Educational Radio Net

The Basics for the New Ham, Bob, No. 75

2009-10-28T20:00:00.000-07:00

Here are a few questions provided by Mike, KF7DTI for the newer ham...

What is “Legal” (1500 watts) vs. Proper ( 5 to 20 watts) and why…
First of all, let's look at what the legal limit is: 1,500 watts PEP (Peak Envelope Power) this is defined as the average power provided to the transmission line over one cycle where the envelope is at it's peak. The envelope is the carrier plus the modulation, so it is the average power of the signal at it's highest modulation. This gives a good indication of the likelihood of the signal to interfere with neighboring frequencies.

So now we get to the real question, what is proper. Well the regulations have something to say about that too. We are required to use the lowest amount of power to accomplish the communications we are trying to do. This is definitely a gray area and a guideline rather than a hard and fast rule. Sometimes it can be obvious, you don't need 50 watts to talk on 2 meter simplex to your neighbor a few blocks away. Sometimes it is not obvious at all, just how much power do you need to be heard by that rare DX station in a South Seas island that dozens of other hams are also trying to reach. There are endless possibilities for arguments here but this is a sort of "good faith" rule. You need to use your own best judgment to decide how much power is necessary.

The other reason to use less power is personal safety. I won't go into the specifics but there is good reason that your handheld doesn't put out more than about 5 watts. If you want to use your mobile rig as a portable, as many of us in emergency communications do, it is important to get the antenna away from your body and anyone elses. Just how far is another judgment call but it helps if you also have it up high so that when it is radiating primarily in the horizontal direction, it will be above your and everyone else's heads.

Proper handling of my unit .. will my Mobile work OK in the Freezing snow?.. 110 degree Desert Sun?... pouring Rain?

Your mobile rig is designed to stay in a vehicle and to operate in one too. There are a handful of new weather-proof and even water-proof rigs on the market but leaving those out, you should use your rig where it will be kept dry and reasonably clean. As for cold and heat, you should check your owner's manual to be sure but generally you can do very well in the cold. When it gets hot you run the risk of overheating your rig when you run full power. Once again, this is a gray area. You can run at a pretty high ambient temperature as long as you use low power. The more power you use, the lower the ambient temperature has to be.

What happens when my batteries get low?.. How can I tell?

I assume you mean your portable here. You should here a beep to tell you. HT's are notorious for beeping about 5 seconds before they shutdown. None of the HT's that I'm aware of have battery charge indicators. I may be wrong about this and if anyone knows of ones that do please speak up.

Why is my brand new Mobile that I just put in my old TRUCK so staticy?
There are a couple of possible reasons. The most likely is the old truck itself. It is either emitting radiation from sparking or other electronics or it is causing fluctuations in the voltage where you are hooking up your radio. For this reason it is usually suggested to connect your radio directly to the battery, properly fused of course. Then all you have to worry about is the radiation caused by your truck. The only way I know to diagnose and fix it is to try putting some filters on the wires and see what happens. But this is a well known problem and there is a lot out there already to help diagnose it. One reason it happens is that mobile and HT rigs usually don't have the good filtering that base stations do. You can pay a lot for a Motorola or other rig designed for professional use in high radiation environments and do a lot better.

I can use my old CB Radio Antenna as my Mobile antenna right?
I wouldn't try it. Antennas are a huge subject that has been covered in various ERN's. You can check the blog for more info. In general, you can probably modify an old CB antenna if you know what you are doing to make it work for amateur radio, but you are almost certainly better buying an antenna build to do the job. Or you can make your own from scratch. Most people don't make their mobile anteannas though, that is better suited for base operations.

What is SWR and why do I care? (that is a good subject)
SWR has been covered a few times and Lee has an exhaustive set of lectures on fundamental electronics leading up to impedance. In short, SWR, the Standing Wave Ratio, is a measure of how much of an electronic signal that you are transmitting, is reflected at a junction. The cause of the reflection is an impedance mismatch at the junction. For example, if you connected your transceiver that has an impediance at it's output of 50 ohms to 75 ohm cable, you will get an impedance mismatch that will cause a high SWR. Since most of us know to use 50 ohm cable the mismatch almost always comes at the connection to the antenna. The impedance at the connection to an antenna is a very complex subject and can depend on the antenna height above ground and other factors. For VHF/UHF it is simplified by the fact that the antenna is high above the ground compared to the wavelength so there is little variation. That's why you can buy an antenna with a 50 ohm connector and be pretty confident that it actually is 50 ohms.

What does QSL, QTH, QRV, 73… etc. mean?.. When is OK to use “Shorthand” like that?
QSL, QTH, QRV and other three letter combinations starting with Q are known as Q signals. They come to us from the days of CW where it was worthwhile to have a shortcut for some commonly used phrases. Q was chosen since it is almost always followed by U so that by creating these combinations, not using U you could be assured that it was not a word. If the Q signal is followed by a question mark it means that it is a question, if no question mark then it is a positive statement.

For example, probably the most common one heard is QSL. You will hear it in place of Roger, Acknowledged, etc. It means, "I acknowledge receipt" or with a question mark, "Do you acknowledge receipt." This is also the reason for QSL cards, which are an acknowledgment of receipt of a contact form another station. These are used to prove that you made a contact with that rare DX station. By the way DX is just shorthand for distance and means a long distance, usually international.

73 goes back a long way as well and just means, "Best Wishes"

There are no hard and fast rules about using these. The most important thing to keep in mind is that you want to make yourself clearly understood. If the person or people you are communicating with understand the Q signals it is fine to use them.

ASCII one oh one, Lee Bond N7KC

2009-10-21T21:07:00.000-07:00

October 21, 2009 Educational Radio Net, PSRG 74th Session

Have you ever wondered about the relationship between computers and data entry? What really happens when you hit a key on your computer and the corresponding character pops up on the monitor? If you are old enough to remember the Mits Altair or IMSAI 8 bit microcomputers then you will have no problem answering these two lead in questions.

Surely one of the oldest schemes for encoding alphabetical characters and numerals is the code developed by Samuel Morse and is known as Morse code. Early amateur radio operators had no choice but to learn the code in order to communicate with their fellow hams. The railroad telegraphers code is a variant of the Morse code and both the radio and railroad schemes were the backbone of the early communications industry.

As telecommunications technique improved the mechanical tele-printer based on the 5 level Baudot code was introduced. Communications was much easier when typing replaced the telegraph key and the distant output was in easily read text. Since only 5 symbols were used the number of possible combinations was limited to 32. If you count all the letters of the alphabet, both lower and upper case, and the numerals 0 through 9, and various punctuation characters it is clear that even a shifted 32 will not do the job.

During the late 50’s, when the early mainframe computers were evolving, it was obvious that something had to be done to improve the encoding of alpha-numerical character information that would be fed to the room sized digital monsters that glowed in the dark.

Enter ASCII, pronounced ass-key, the acronym for American Standard Code for Information Interchange. ASCII is a 7 bit code hence 128 unique bit pattern combinations are possible. Enough combinations to represent all the upper and lower case alphabetical characters plus numbers plus punctuation plus special formatting characters in use at the time. The first meeting of the committee which adopted this code was in 1960. The code later became known as US ASCII since it was only good for English systems.

During this time frame IBM developed a proprietary code known as EBCDIC which was based on all possible combinations of the 8 bits in a byte. There are 256 possible unique combinations of 8 bits so EBCDIC offered twice as many possibilities as did ASCII. EBCDIC was used in the large mainframe computers that IBM produced and ASCII became the standard coding scheme for the micro-computing industry.

From the late 50’s until recently the use of US ASCII dominated the microcomputer industry and information exchange on the Internet. Today ASCII is taking a back seat to the Unicode in its various implementations as UTF-8, UTF-16, or UTF-32 as in Unicode Transformation Format. Using 16 bits, or a word, offers over 65 thousand unique possibilities so numerous languages can be represented in addition to English and this makes the encoding truly universal and a natural for Internet use.

Historically ASCII is a 7 bit code. Always has been and always will be. However, that inviting 8th bit in the word could be useful and double the number of coding possibilities. Implementations of ASCII using all 8 bits became known as "extended" ASCII and found much use for formatting characters and such when word processing came to fore. Other names were "upper" level ASCII in contrast to the original "lower" level scheme.

Let’s look at 7 bit ASCII in some detail to see how it is structured.

Referring to the Bits, Nybles, Bytes, and Words (presentation 71) a few weeks ago we know that computers like to operate with patterns of 4 bits (a nyble), 8 bits (a byte), or 16 bits (a word). If ASCII requires 7 bits then the best choice for a pattern would be the next largest set or byte consisting of an assemblage of 8 bits. The extra 8th bit became useful as a rudimentary error detecting bit and was called the parity bit. More on this later.

A table of the ASCII characters is generally shown as 16 rows and 8 columns. The multiple of 16x8 is 128 so this array matches all the combination possibilities of 7 bits. The first two columns from the left contain all of the, so called, formatting characters, the third column from the left is where you find the various punctuation symbols and math symbols, the fourth column from the left lists the numerical symbols, and the last four columns are the upper and lower case alphabetical symbols.

To identify any one of 16 rows requires 4 bits and the lower 4 bits of the 7 bits is used as the row identifier where bit 1 is least significant. To identify any one of the 8 columns requires 3 bits and the bits 5, 6, and 7 (most significant) are used for this purpose. So, to recap… bits 1, 2, 3, and 4 are used to identify in which row a character is located and bits 5, 6, and 7 are used to identify in which column a character is located. Every box in the array is uniquely identified by a bit pattern. Bit 8 is always a zero unless the optional parity possibility is in play.

The data entry and identification process goes like this. Suppose you depress the capital or upper case "H" key on your keyboard. Bit 7 is forced to a "1" and 6 and 5 remain at zero. Bit 4 is forced to a "1" and bits 3, 2, and 1 remain at zero. Finally the "H" is coded as 01001000 or 48h in shorthand hexadecimal notation. This bit pattern is sent to the computer where it is checked, pattern by pattern, against a table looking for a match. When the match is found the computer proper knows which key was pressed.

Any error in this transmission process is serious since the computer will interpret your intended bit pattern incorrectly. The 8th bit or parity bit allows a low level error check as follows. Parity can be defined as even or odd. If you choose even then if the sum of the 7 bit 1’s is odd you just force bit 8 to a 1 and the overall number of 1 bits is even. If the sum of the 1 bits is even then leave the 8th bit at zero. This same process holds for odd parity. On the receiving end the system will check the count to determine if parity is correct. This scheme will detect all 1 bit errors or odd multiples thereof.

In summary, bits 5, 6, and 7 determine a column and indicate if the symbol is formatting, a number, or alphabetical character. Bits 1, 2, 3, and 4 determine which character of the alphabet or which number or which formatting symbol is to be used.

This concludes the set up discussion for ASCII one oh one. Are there any questions or comments with regard to tonight's discussion topic?

This is N7KC for the Wednesday night Educational Radio Net

The Future of the Educational Radio Net

2009-10-20T00:49:00.000-07:00

Lee and I are considering ending our involvement with the Educational Radio Net. If we do, it will very likely end the net itself.

This has been a labor of love for the two of us. It is a fair amount of work to come up with new subjects each week, research them and write the scripts for them. Getting on the air and doing the net is the payoff. What has kept us going has been the interest and participation of the hams checking in to the net. Lately that interest has fallen off somewhat. We both agree that we do not wish to continue as it is going now.

We are soliciting ideas, suggestions, questions, etc. to assist us with creating future nets. We are also looking to add to our base of regular contributors.

To give your suggestions, please contact Lee Bond: n7kc@comcast.net

We are very grateful for the contributions from those listed below. They have helped sustain the net.
John Pollock, K7MCX
Jim Hadlock, K7WA
Brian Daly, WB7OML
Curt Black, WR5J
Boone Barker, KC7RK

Extra Class Exam Grab Bag, Bob, No. 73

2009-10-14T19:23:00.000-07:00

Tonight was supposed to be about current use of Spread Spectrum in Ham Radio but I couldn't find any information about it. If anyone on frequency knows about it or knows where to point me to look please let me know.

Instead, tonight I will discuss a few test questions from the Extra Class exam.

E9B08 (C)
How does the total amount of radiation emitted by a directional (gain) antenna compare with the total amount of radiation emitted from an isotropic antenna, assuming each is driven by the same amount of power?
A. The total amount of radiation from the directional antenna is increased by the gain of the antenna
B. The total amount of radiation from the directional antenna is stronger by its front to back ratio
C. There is no difference between the two antennas
D. The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna

The important point to take away from this is that the total radiation depends solely on the amount of power that is transferred to the antenna. What the antenna design can do is shape or focus that radiation so that more goes in the direction you want and less in the directions you don't want.

E9D06 (C)
Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?
A. To swamp out harmonics
B. To maximize losses
C. To minimize losses
D. To minimize the Q

The reactance in the loading coil doesn't contribute to heat loss. All heat loss comes from resistance. Resistance acts directly on current, converting it to heat. Reactance, being out of phase with current, doesn't produce heat and doesn't contribute to losses.

E9D08 (B)
What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?
A. It is increased
B. It is decreased
C. No change occurs
D. It becomes flat

E9D14(B)
Which of the following types of conductor would be best for minimizing losses in a station's RF ground system?
A. A resistive wire, such as a spark-plug wire
B. A thin, flat copper strap several inches wide
C. A cable with 6 or 7 18-gauge conductors in parallel
D. A single 12 or 10 gauge stainless steel wire

The reason for the thin, flat copper strap is that it increases the Capacitive reactance vs. the Inductive reactance making the strap less likely to become resonant. For similar reasons the RF ground strap should be as short as possible.

E9D15 (C)
Which of these choices would provide the best RF ground for your station?
A. A 50-ohm resistor connected to ground
B. A connection to a metal water pipe
C. A connection to 3 or 4 interconnected ground rods driven into the Earth
D. A connection to 3 or 4 interconnected ground rods via a series RF choke

We want a very low impedance path directly to earth ground. We are not trying to match impedance here, just reduce it, so no resistors or chokes. The metal water pipe might serve as a safety ground, although today, more and more pipes are PVC so don't count on that metal pipe you are connecting to, to be metal the entire length. But even so, an all metal pipe system in your house makes a pretty active antenna system in itself. This is not what you want for your RF ground. The short-run ground strap to interconnected ground rods in the Earth is the way to go.

Digital Summer Notes, Boone Barker, KC7RK, No. 72

2009-10-06T16:16:00.000-07:00

Notes from Curt Black's“Summer of Digital Communications Fun”

By Boone Barker, KC7RKOctober 3, 2009

I was a student in the ham radio class taught by Curt Black WR5Jduring the summer of 2009. Included in the class were Lee N7KC, Bob K9PQ, TammyWA7TZ, Glen K7GLE and others. We learned about and experimented with a varietyof digital communication modes, many of which could be useful for emergencycommunications. I know that everyone who participated enjoyed the challenge oflearning about digital communications. We all owe Curt a huge debt of gratitudefor his success in making this a fun experience.

This paper is my effort to recap the summer sessions and some keypoints that I wanted to remember. Full descriptions and more are in theWA-DIGITAL Yahoo Group site at http://groups.yahoo.com/group/wa‑digital/.

Overview

Students met Wednesday evenings from June 6 through August 26,2009, on the PSRG Seattle repeater (146.960 MHz) for the Educational Radio Nethosted by Curt Black, WR5J.

All 12 sessions were written and led by Curt– EnvironmentalScientist – ham for ¼ century—had a packet network then in Texas. Also anaturalist – birds and bats and nature in general – Sound Recordist.

Curt emphasized that nearly everything came from the internetsomewhere and sources were cited each time. Only of little of the informationwas based on direct communication with the authors of the software—only when hehad questions on how to make something work or what was the current bestapproach for achieving some objective.

Training purpose: explore and experiment with a variety ofdigital communication modes over radio.

The WA-DIGITAL Yahoo Group established at http://groups.yahoo.com/group/wa‑digital/for this topic has extensive files and messages on this topic, including a BlogPost script for each session. The information below is only a very briefsummary of each session; go to the corresponding Blog Post for completedirections and information.

Session scripts were also posted on the PSRG Educational RadioNet blog at http://www.educationalradionet.blogspot.com/and are still there.

Participants were asked to have a computer, VHF and HF radiosand—eventually—a sound card interface, home-brew or purchased.

Session 1 - Intro to Digital Communication, Software and Modes

Planned activity for the summer

Session 1 Intro to DigitalCommunication, Software and Modes

Session 2 Intro to FLDIGI –Install, Setup and Mode Selection

Session 3 Using FLDIGI – Startingwith PSK-31 and Transmitting a Good Signal

Session 4 More FLDIGI – RTTY, theWRAP Utility and RS-ID

Session 5 WSPR – Weak SignalPropagation Reporter

Session 6 MMSSTV Slow Scan ImageTransmission

Session 7 Digital SSTV EasyPAL

Session 8 WSJT-JT65A – TerrestrialHF

Session 9 WSJT-HS-Meteor Scatter

Session 10 Packet Radio UsingFlex32

Session 11 Packet Radio Using AGWPacket Engine

Session 12 WINDRM – Digital Voice

Soundcard to radio interface options

Acoustic coupling: microphone feeding shack audio intoyour computer and the rig audio softly coming out of a speaker in the roomwith you fairly close to the mic
Hardware: range from very simple ones for a few bucks to$100 for a Tigertronics SignaLink USB. If you want to keep going you cango up to a $369 US Interface Navigator - Lots of choices.

[See http://www.kc2rlm.info/soundcardpacket/1cablestart.htmand http://uspacket.org/network/index.php/topic,21.msg23/topicseen.html#newfor DIY soundcard interfaces.]

Software now available

Multifunctional: Multipsk, MixW, Ham Radio Deluxeand FLDIGI
Specialized: Digipan, MMSSTV, EasyPal, WSPR, WSJT,Flex32
Interface: AGW Packet Engine, Packet Engine Pro
Winlink: Airmail, Paclink

Assignment: install FLDIGI and get ready to receive at thenext session.

Session 2 - Intro to FLDIGI – Install, Setup and Mode Selection

The group owes much of what we know about FLDIGI and the NarrowBand Emergency Messaging System (NBEMS) to the Pennsylvania group at http://wpanbems.org/ .

Fast Light Digital Modem Application(FLDIGI) Software by W1HKJ and Friends (http://www.w1hkj.com/)

Modes:

CW AFCW (A2).
DominoEX: (4,5,8,11,16,22)
Hell: Feld Hell, Slow Hell, Feld Hell 5, Feld Hell 9, FSKHell, FSK Hell-105, Hell 80
MFSK: from 4 to 64 tones
MT63: 500, 1000, 2000 Hz bandwidths
Olivia: – several flavors from 250 to 1000Hz bandwidth andwith from 8 to 32 tones
PSK: BPSK-31, QPSK-31, BPSK- 63, QPSK-63, BPSK- 125, QPSK125, BPSK-250, QPSK-250
RTTY: 45 baud, 50-baud, 75-baud
Thor: (4, 5, 8, 11, 16, 22)
Throb: (1, 2, 4)
WWV: calibration of soundcard oscillator)
Frequency Analysis: measure the frequency of a remotesignal that is transmitting a steady carrier.
Tune: generates a continuous single frequency audio signalat the exact frequency to which the waterfall cursor has been set

To Install the Software:

See Blog Post 2 in the WA-DIGITAL group files for detailedinstructions. A summary: Go to the web site at http://www.pa-sitrep.com/NBEMS . Followsteps on the left side of the page to get the FLDIGI software, install, andconfigure it. Calibrate your sound card offsets by downloading and running CheckSRfrom http://www.pa-sitrep.com/NBEMS/fldigi_calibration.htm. Also download and install NBEMS macros from http://www.pa-sitrep.com/NBEMS/fldigi_macro.htm.

Application Notes

Win XP users should load FLDIGI 3.12.4. Vista OSusers should install FLDIGI 3.11.4-WinV (available at http://groups.yahoo.com/group/wa-digital/) until bugs in the later version are fixed.
Bookmark fldigi on-line help at http://www.w1hkj.com/FldigiHelp/index.htmland go to it for info on various modes, and for an index of sights andsounds of digital modes.
Install QuickMix by Product Technology Partners at http://www.msaxon.com/quickmix/.This is a simple applet that allows you to store all or part of thecurrent state of your audio mixer in a settings file, and to restore themixer to that state whenever you want.

Try out FLDIGI using some of the following modes andfrequencies.

PSK – narrow band low symbol rate modes usingsingle carrier differential Binary Phase Shift Keying, BPSK, or QuadraturePhase Shift Keying, QPSK. This is the most popular digital mode by far. CommonPSK31 frequencies:Daytime: 14.070 MHz/USB, 10.140 MHz/USB, 7.070 MHz/USBEvenings/Night: 3.580 MHz/USB, 7.070 MHz/USB, 10.140 MHz/USB

MT63 employs a unique highly redundant Forward ErrorCorrection system which contributes to it robustness in the face ofinterference and fading.

MT63 FM 6m/2m/70cm ops (2K Long Interleave)
MT63 HF USB ops – (1K/Long Interleave):NBEMS recommended USB frequencies: 3.590, 7.090, 14.109 MHz

Olivia is a very robust mode with lowerror rates, but can be annoyingly slow.

HF USB ops – (500Hz/16 Tones): NBEMS recommended USBfrequencies: 3.584, 7.074, 14.074 MHz

[See http://hflink.com/olivia/for a full list of Olivia calling frequencies.]

Domino The mode is normally usedwithout Forward Error Correction, as it is very robust. The default speed (11baud) was designed for NVIS conditions (80m at night), and other speeds suitweak signal LF, and high speed HF use. The use of incremental keying gives themode complete immunity to transmitter-receiver frequency offset, drift andexcellent rejection of propagation induced Doppler.

Default calling mode - DominoEX11. NBEMS recommended USBfrequencies: 3.583, 7.073, 14.073 MHz

Feld Hell frequencies 3.580, 7.037, 10.137, 14.0635, 21.063,28.120 MHz

Description of Feld Hell is at http://www.qsl.net/zl1bpu/FUZZY/Feld.htm

Session 3 Using FLDIGI – Starting with PSK-31 and Transmitting a GoodSignal

Recommended reading: Clint Hurd KK7UK presentation at AlaskaHamfest in 2008: go to http://kk7uq.com/html/hamfest.htmand click on Digital Communication Basics.

Hints to new PSK users from that presentation:

Make sure you are putting out a pure signal. Don'toverdrive the rig.
Ask on the bands for a report from others – the softwareof the person receiving your signal can report your IMD – should be lessthan minus 24dB.
Don't type in all caps.
Lower your power to a level of50% of what your rig can produce so you don’t burn out your finals.
Tune a little above the PSKactivity and call with Hell or MFSK16 or Olivia 16/500.

All PSK31 frequencies

160meters 1.838 MHz

80meters 3.580 MHz

40meters 7.035 MHz

30meters 10.140 MHz

20meters 14.070 MHz

17meters 18.100 MHz

15meters 21.080 MHz

10meters 28.120 MHz

6meters 50.290 MHz

2meters 144.144 MHz

1.25meters 222.07 MHz

70centimeters 432.2 MHz

33centimeters 909 MHz

Note: you will frequently see the wider signals of PSK63 justa little higher.

Session 4 More FLDIGI – RTTY, the WRAP Utility and RS-ID

More features of FLDIGI described in Blog Post 4

Macros: content can be edited byright clicking on the button. Other sets can be accessed by clicking on the endof the bar. Left or right clicking on the mode button brings up options.

Waterfall: the size can beadjusted and magnified.

2-minutes buffer: constantlysaving the audio so that a new signal in a different mode can be selected fordecoding of that last 2 minutes.

Signal to noise and intermodulationdistortion of a received signal are displayed on the bottom of the screen.

The Wrap Utility (downloaded with FLDIGI)

Wrap allows you to transmit a text message, image, or binary fileto either single or multiple stations and allow each receiving station toverify that the transmission was received without error. Blog Post 4 hasdetailed instructions for configuring FLDIGI, converting and sending a“wrapped” message, and receiving and decoding wrapped messages.

RS-ID

The "RS" ("RS" for "Reed-Solomon")identifier allows automatic identification any digital transmission done in oneof the RX/TX modes handled by FLDIGI if the sending station is using thefeature. In receive mode it can be activated by clicking on the RSID button inupper right.

RTTY (Radio Teletype) is the second most common digitalmode.

Look to the following websites for RTTY guidance:

Getting Started in RTTY with MMTTY athttp://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13022
An RTTY Tutorial for Beginners by Bill W7TI is athttp://www.iw5edi.com/ham-radio/26/a-rtty-tutorial-for-beginners

RTTY frequencies:

80 meters: 3580 - 3650 (3520 - 3525in Japan)

40 meters: 7080 - 7100 in the US (see note below)

30 meters: 10110 to top of band

20 meters: 14080 - 14099 (avoid theNCDXF beacons at 14100)

15 meters: 21080 - 21100

10 meters: 28080 – 28100

Note: RTTY allocations for 40 meters vary greatly all overthe world. In the US, RTTY is permitted between 7000 and 7150, although most US activity is between 7080 and 7100. DX activity is often found between 7020 and 7045. TheARRL promotes 7040 as the RTTY DX calling frequency, but the CW QRP’ers use itas their calling frequency too.

Three main digital packages are:

FLDIGI by David Freese, W1HKJ and Skip Teller, KH6TY: http://www.w1hkj.com/

HRD/DM780 by Simon Brown, HB9DRV: http://www.ham-radio-deluxe.com/

MULTIPSK by Patrick Lindecker, F6CTE: http://f6cte.free.fr/index_anglais.htm

Patrick’s MULTIPSK is a great technical achievement. He offersthe most sensitive modems and detection routines available and many modes (suchas ALE-400) that are not available in any other software. The challenge is hisuser interface is very dense and can be tough on a first-time user. Hisphilosophy is he wants all the controls in one place – and they are.

FLDIGI is a very elegant package that is fully featured butsimple to setup and use. HRD is not so simple, but is a great package and whenused with DM780 is very fully featured. MULTIPSK offers the most sensitivemodems and detection routines available and many modes (such as ALE-400) thatare not available in any other software. The challenge is his user interface isvery dense and can be tough on a first-time user.

Other packages of significance

WINWARBLER, part of the DXLAB suite and available here: http://www.dxlabsuite.com/winwarbler/download.htm

DIGIPAN – by Skip Teller KH6 and one of the authors of FLDIGI anda founding father of digital modes in amateur radio: http://home.comcast.net/~hteller/digipan/

MixW – updated in Jan, 2009 after a long hiatus. Payment of $50required after a 15-day trial period. http://www.mixw.net/index.php?j=downloads

Check out this repository of digital and other ham radiosoftware: http://www.g3vfp.org/download.html

Session 5 WSPR – Weak Signal Propagation Reporter

Joe Taylor, K1JT, of Princeton has written a series of programsfor brilliantly combining Digital Signal Processing (DSP) and ham radio toallow us to plumb the depths of weak signal work. WSPR (pronounced"whisper") stands for "Weak Signal Propagation Reporter."This program is designed for sending and receiving low-power transmissions totest propagation paths on the MF and HF bands. Users with internet access canwatch results in real time at http://wsprnet.org/drupal/.

Downloads for Windows and documentation are at http://physics.princeton.edu/pulsar/K1JT/wspr.html.Follow the Quick Start Guide to install and configure.

Application notes

Soundcard: In Configure>Options, enter the numbers fromthe “Audio Device” list on the black WSPR screen that comes up at startup. Notethat power is in dBm.

Frequency settings are automatic. Just choose the band.

Install Dimension 4 from Thinking Man Software at http://www.thinkman.com/dimension4/download.htmto keep your computer clock accurate to within 0.01 sec.

This is a weak signal mode – it really doesn’t need muchpower – try 1 watt (30 dBm) and see who hears you and where they are.

Try operating at local sunrise or sunset to really seewhat happens as the bands change.

Session 6 MMSSTV, Slow Scan Image Transmission

Download MMSSTV from http://mmhamsoft.amateur-radio.ca/mmsstv/

Install and configure it using the Help file in theprogram, or instructions in the WA-DIGITAL Yahoo Group files.

Most common modes: Scotty 1 or Scotty 2 in US. Martin 1 or2 for DX.

Suggested SSTV frequencies:

· 10 Meters:28.67328.67728.680=calling frequency28.68328.68628.690=K3ASI repeater28.700=ON4VRB repeater

· 15 Meters:21.33421.33721.340=calling frequency21.34321.346Avoid SSTV around 21.350 because there is a Phone DX Net running

· 20 Meters:14.230=calling frequency14.23314.23614.239Avoid SSTV on 14.227 because there is a Phone DX Net running there.

Application Notes

Soundcard oscillator calibration is critical to avoidtransmitting slanted images. See “Slant Correction” in the Help menu.

To use this software, just go to the SSTV watering holes at14.230 or 14.233. This is the best known and possibly the best defendedfrequency in all of amateur radio.

The Ten Commandments of Slowscan by Dave Jones - KB4YZ

Use voice before sending SSTV.
Wait for voice and SSTV traffic to finish before sendingSSTV.
Choose an SSTV mode that is proper for the image to besent, band conditions, and the receive capability of the receivingstations.
Announce the SSTV mode used prior to sending.
Transmit on frequency as confirmed by calibration of theVFO with WWV.
Send straight pictures as confirmed by calibration of theclock timing with WWV.
Send quality pictures with call sign on image.
Send full frame.
Avoid sending a CW ID unless required by regulations.
Describe the picture only after it is confirmed that itwas properly received.

Session 7 Digital SSTV: EasyPAL

EasyPAL is a piece of software by Erik VK4AES that usesDRM encoding and allows us to send any type of file on your computer, includingimages. We can request “fills” or retransmission of any blocks not receivedperfectly. Or you can Reed-Solomon encode everything you send to increase theprobability your information will make it through the first time.

Download the software from http://www.g4rob.co.uk/easypal.htmand go to the help file on that web site for configuration instructions andhelp files.

SSTV frequencies are listed above.

Application notes

Soundcard volume settings are critical. Too high or toolow a signal level from your Receiver via your Radio Interface to your PCsoundcard will result in Total or partial LOSS OF RECEIVE SIGNAL. EasyPal willcorrectly receive and decode when ALL RECEIVE INDICATORS SHOW GREEN. Get itright and then use QuickMix to save settings for this application.

Go to Setup>Calibrate Waterfall (WWV) to use WWV signals to calibratewaterfall frequency scale.

[N.B. EasyPal could be a powerful tool for emcomm. It could be usedto transmit a standard ICS form along with photos from the field to the EOC.]

Session 8 WSJT-JT65A – Terrestrial HF

The WJT Software was also written by Joe Taylor, K1JT. Itfacilitates basic digital communication using protocols explicitly optimized fora number of different propagation modes. Specifically:

FSK441 for meteor scatter
JT6M for ionospheric scatter
JT65 for EME at VHF/UHF, and for HF skywave propagation

Download for Windows is at http://physics.princeton.edu/pulsar/K1JT/wsjt.html. The user’s guide is included with the download.

JT65 has three sub-modes known as JT65A, B, and C. They areidentical except for the spacing between transmitted tone intervals. At thepresent time JT65A is generally used on HF and 50 MHz, JT65B on 144 and 432MHz, and JT65C on 1296 MHz. JT65 uses 60 second transmission and receptionintervals.

Andy K3UK has an excellent JT65A guide at http://www.obriensweb.com/bozoguidejt65a.htm

By far the simplest method of figuring out where the action canbe found is to use your web browser and go to the JT65 Terrestrial Link website by N0UK at http://www.chris.org/cgi‑bin/jt65talk.

The most commonly used JT65A frequencies are:14.075 to 14.0767.0757.076 in North America7.042 to 7.0437.025 LSB for Europe and Oceania3.576 (North America)3.796 (Europe)18.102 & 18.10610.14721.07624.9101.805 to 1.808.

14.076 or 10.147 or 7.076 are the best places to start. These areDIAL frequencies.

Application Notes

Important: use the WSJT7 black and white DOS-like windowto check your input and output device numbers –then transfer that info to thecolorful WSJT7 by K1JT window - look under the SETUP menu - OPTIONS choice andenter the AUDIO IN and AUDIO OUT device numbers you got from the first columnon the DOS-like black window.

As before, input volume level is critical.

Soundcard oscillator calibration is also important. Seethe help files.

Operating with WSJT

By longstanding tradition, a minimal valid QSO requires theexchange of call signs, a signal report or some other information, andacknowledgments. WSJT is designed to facilitate making such minimal QSOs underdifficult conditions, and the process can be made easier if you follow standardoperating practices. The recommended procedure is as follows:

1. If you have received less than both calls from the otherstation, send both calls.

2. If you have received both calls, send both calls and asignal report.

3. If you have received both calls and a report, send R plusyour signal report.

4. If you have received R plus signal report, send RRR.

5. If you have received RRR — that is, a definiteacknowledgment of all of your information — the QSO is “officially” complete.However, the other station may not know this, so it is conventional to send 73s(or some other conversational information) to signify that you are done.

Typing the F5 key will cause WSJT to pop up a screen thatreminds you of the recommended procedures.

Digital on Six at http://www.ykc.com/wa5ufh/DOS/index.htmlpromotes the use of digital modes on the 6 meter band. A weekly event is theJT65B activity on Friday evenings in 2 phases: 9:00 pm Eastern and then 8:00 pmPacific time. Default Mode JT65B on 50.294MHz. When the "Band IsOpen" QSY to PSK / Olivia / etc.on that mode’s appropriate calling frequency.50.260 WSJT Modes (Calling Frequency)50.290 PSK3150.2925 Olivia50.294 JT65B & Friday Activity Period Calling Frequency50.300 RTTY and MFSK

Session 9 WSJT-High Speed-Meteor Scatter

WSJT/FSK441 is now the primary meteor scatter programand mode over nearly all the world.

Go to http://www.qsl.net/w8wn/hscw/papers/fsk-sop.htmlfor Standard Operating Procedures for FSK441 meteor scatter communicationswithin the Americas. Read this!

Go to Ping Jockey Central at http://www.pingjockey.net/cgi-bin/pingtalkand click on “read this!” at the top of the page to see Ping Jockey Etiquette.On that page are messages from ongoing HSMS scheds and contacts.

Go to http://www.ykc.com/wa5ufh/for the WSJT Group –information and news about meteor scatter,including Random Hour operations on Saturday and Sunday mornings. See also the WSTJYahoo group.

Application Notes

Computer clock must be accurate.

In North America, 50.260 MHz and 144.140 MHz are calling(CQ) frequencies—not operating frequencies. Schedules should alwaysbe made at least 5 kHz away from the calling (CQ) frequencies.

"CQU5" means "I'm listening and will reply Up 5kHz.""CQD8" means "I'm listening and will reply Down 8 kHz".The offset frequency is always relative to the CQ frequency.

“CQ123” means "I'm listening and will reply on 144.123 MHz."

The commonly-accepted (and expected) exchange for all HSMSoperation is the burst duration-signal strength report("2-number" report).

First Number: Ping Duration	Second Number: Signal Strength
1 - Ping with no info. (Not sent)
2 - ping, up to 5 sec in length	6 - up to S3 in strength
3 - 5-15 sec in length	7 - S4 to S5
4 - 15-60 sec burst	8 - S6 to S7
5 - over 60 sec burst	9 - S8 and stronger

Best time for MS operations is in the morning hours,around 0600 local time, when that part of the earth is facing the samedirection as the direction of travel of the earth in its orbit around the sun.

Session 10 Packet Radio Using Flex32 and Paxon

Soundcard packet makes amateur packet radio available to any Hamwith a VHF transceiver and a soundcard-equipped computer, at little or noexpense.

For the classic “Introduction to Packet Radio” by Larry Kenney,WB9LOZ, go to http://www.choisser.com/packet/.

Flex32 Software written by Gunter Jost DK7WJ

Go to http://uspacket.org/network/index.php/topic,21.msg23/topicseen.html#newfor a tutorial by Charles Brabham N5PVL with download and installationinstructions. Two programs are downloaded:flexnet32.zip this file contains the Flex32 software, some assorteddrivers, and a simple terminal program andsoundmodem-flex.zip this is the soundcard driver module, along with asetup utility.

Installation: See Blog Post 10 for details. Briefly: Unzipinto C:\FLEX32. Run soundmodem.config to configure soundcard driver. RunFlexctl.exe to bring up the Flexnet Control Center and add “soundmodem” to thechannel parameters. Create a command-line shortcut to Tnc32.exe with parameters“call‑sign 4 4” to bring up TNC32. Key Esc to enter commandmode and key H to list available commands. This is a simple terminal programthat may be used to connect to a packet network

In Seattle, connect to SEA on 145.010 MHz.

Paxon software written by Ulf Haueisen DG1FAZ

Go to http://uspacket.org/network/index.php/topic,20.0.htmlfor another tutorial by Charles Brabham N5PVL with download and configuration instructions.The web-site, help files and installation program for Paxon are all in German,but the program comes up ready for English speaking users. However, the helpfile is still in German.

Paxon download is at http://www.paxon.de/download.htmlfor download. See Blog Post 10 for details of installation and configuration.

First Steps are listed in the Help tab

Click on Tools, Settings.

Select General, My Calls, Add.

Enter your Callsign and specify theconnectable SSIDs.

Setup your Modems and TNCs:Devices, Device drivers, Add.

Select Flexnet or Hostmode.

Select your devices in the list,and edit their Properties.

Confirm the settings with the OK-Button.

Click on Connect to make your firstconnect with Paxon. Have Fun!

Try browsing around in Paxon's "Settings" and you willbe amazed at all of the nice things this program can do. It can be used forfile transfers, remote SYSOP'ing, and as a personal terminal.

Session 11 Packet Radio Using AGW Packet Engine

AGW Packet Engine by George Rossopoylos SV2AGW handles allthe traffic between packet applications and the computer/radio interface—TNC orsoundcard. It is freeware from the SV2AGW web site at http://www.sv2agw.com/ham/ in the “Downloads”section. A lengthy tutorial by Ralph Milnes KC2RLM for installation andconfiguration is located at http://www.kc2rlm.info/soundcardpacket. See Blog Post 11 for details.

A full featured version is Packet Engine Pro, with one month freeand then $59 license fee. The SV2AGW web site also has software downloads forAGWTerminal and AGWMonitor, both useful accompaniments to AGWPE.

Application Notes

When you configure a radioport in AGWPE for SignaLink USB, selectan unused printer port (LPT3) as your PTT port.

Always format packet and WL2K messages in plain text. HTML formatadds unnecessary bytes to the message.

For use with Airmail software, download and install AM to PEsoftware by Brian Smith KG9OG from http://www.qsl.net/mararc/ampe.htm.

Session 12 WinDRM—Digital Data and VoiceUsing Digital Radio Mondiale on the Ham Bands

The problem with digital voice modes is the loss of the use of a proprietarycodec. Digital voice is about dead and probably will remain that wayuntil a MELP equivalent codec is found or some new technology is found. SeeBlog Post 12 for more information.

If you want to try it, here is the link: http://n1su.com/windrm/download.html.14.236 MHz is the calling/net frequency for digital voice.

Postscript

At this writing, the WA-DIGITAL Yahoo Group is active—and thegroup web site at http://groups.yahoo.com/group/wa‑digital/has a large collection of files and information about digital communications forRadio Amateurs. If you are interested in this topic but not yet a member of thegroup, please consider joining.

October 5, 2009

Bits, Nibbles, Bytes, and Words, Lee Bond N7KC

2009-09-30T19:25:00.000-07:00

September 30, 2009 Educational Radio Net, PSRG 71st Session

The digital computer is ubiquitous. These computers are everywhere. Kids have their own and, more than likely, so do the grandparents. Most users are very proficient with the keyboard and blaze through the games, documents, spreadsheets, and whatnot without even a thought of what is going on inside that mysterious box called a computer. I am willing to bet that not one in ten users can define a "bit" and I will further wager that not one in 100 users has a good grasp of computer arithmetic or how the rational coding of bits makes their computer tick.

My task tonight is to lead you down that magic path and explore the idea of the "bit" and how it can be used to represent numbers or events. We will then extend the bit notion into nibbles, bytes, and words. Some of the net participants tonight are likely to be expert in this bit world so, if you quality, think of ways to help me clarify the notion when I break for questions or comments.

Let’s start with our very familiar decimal number system and dissect it in a way that I bet few of you have done. We will concern ourselves only with integers so no fractions are allowed in our discussion. Integers are the numbers 1, 2, 3, etc. that have no fractional part. You may call them whole numbers if you please. Integers can be precisely defined but that would muddy the water a bit so we will dispense with such formalism in favor of simplicity. We will start with the integers 1 through 9 and include the notion of nothingness as in zero.

When we think of the decimal integers we must consider the ordering. For example after nothingness as in zero we think of 1, then 2, then 3, etc. in order through 9. Our standard notion of 9 is that it is ‘bigger’ than 8 and 8 is ‘bigger’ than 7 or 6 or 5, etc. In the following discussion throw ordering out the door. We will not be interested in ordering. In fact we will not even use numbers rather we will choose a collection of identical marbles and call then symbols. So, zero (or nothingness) plus 1 through 9 equals 10 symbols which we represent with 10 marbles.

Unfortunately this forum of ours does not include a chalkboard so we must create a virtual chalkboard in your mind. If it helps then close your eyes and imagine the following: in your mind arrange 6 boxes in a 2 row x 3 column array. Each of the boxes in the top row has 10 identically sized marbles and the row of lower boxes have ‘nothing’ or zero marbles. Just so we do not get marbles in the wrong boxes lets choose black marbles for the rightmost box, brown marbles for the center box, and red marbles for the leftmost box.

Ok, lets do something useful with this scheme. Assume that you are sitting on the back porch looking toward the Cascades and you want to tally lightning strikes. When the first strike occurs you move a black marble from the top right box into the box below. At the next strike you repeat the previous operation and move another black marble from the top right box into the box below. As you notice more and more lightning strikes you move black marbles until you have no more black marbles in the top right box. At this point you have used all of your marbles, so to speak, and you indicate this fact by moving a brown marble into the middle box below then move all of the ‘used’ black marbles back into the top right storage box.

The lightning strikes continue and you move black marbles, one by one, into the lower box until you again run out of marbles. At this point you move a brown marble from the top box into the box below and reload the top box with the black marbles. Eventually you will run out of brown marbles in the top center box so you will move a red marble from the top left box to the box below and reload the top boxes with appropriate black and brown marbles.

The point of this mental exercise is to illustrate that you can tally objects with symbols and that every time you exhaust, or cycle through, your symbol set you just indicate this fact by incrementing the symbol set to the left. You can choose as many symbols as you please. In this example, based on the decimal system with 10 symbols, each box to the left is weighted or "heavier" by 10 with respect to its neighbor to the right. As a result, this 10 symbol scheme goes units, tens, hundreds, thousands, etc. so is very convenient for us mortals. Once you know the weighting you can easily figure out how many lightning strikes you tallied by counting the symbols in each weighted box.

In the interest of time let me assert that you can use a set of 12, or 9 or 8 or 7, etc. symbols and the scheme holds true. Now lets examine the case where we have reduced the set to two symbols. Thinking for a moment you realize that "bi" means two as in binary star or binocular. Could the binary number system be as simple as accounting for just two symbols? The answer is, of course, yes. The beauty of using two symbols in numerical computing is that transistors are very good switches and can be used to represent the two binary states perfectly. A SPST switch normally has two states such that it is either on or off. Open or closed. It is a trivial exercise to arrange a circuit with a mechanical switch such that one switch position results in +5 volts and the other position results in zero volts. The symbols associated with a two state switch are zero and one as in 0 or 1.

Now, in a fashion similar to the decimal box exercise above let’s arrange 8 binary boxes side by side in a row. We know that the state of each of these "binary" boxes can be represented by either a 0 or a 1. Assume that the rightmost box is the, so called, least significant box and that all boxes are in the 0 state. Visually the boxes look like 0000 0000. Now, bump the rightmost box to the 1 state and the visual presentation goes to 0000 0001. Well, the rightmost box has now used all of its symbols so to tally the next event it must return to 0 and the box to the left is bumped from 0 to 1 as in 0000 0010. If you carry this process forward you will eventually achieve 1111 1111 and the next event will change all positions back to 0000 0000. The weighting goes by 2 rather than 10 as in the decimal case so each position to the right is ½ of its left neighbor or each position is twice its neighbor to the right. The sequence is 256, 128, 64, 32, 16, 8, 4, 2, 1. These 8 boxes represent a byte and each of the positions is a binary digit or bit. Two sets of 8 boxes as in 2 bytes or 16 bits represents a binary "word". Half a byte as in 4 bits is a nibble (or nybble to some).

The total number of distinct combinations of 8 bits from 0000 0000 to 1111 1111 is 256 and goes as 2^8. A binary word composed of 16 bits can assume 2^16 or 65,536 distinct combinations. Recall that we are limiting ourselves to positive integers so we are only able to handle numbers up to 65,536. There are schemes to handle signed integers such as 2’s complement arithmetic and to be completely flexible there are floating point schemes which look a lot like scientific notation.

Four binary bits can assume 16 distinct combinations and is the basis of the hexadecimal number system which has symbols 0 through 9 plus A, B, C, D, E, and F. Four binary bits are also used for BCD or binary coded decimal notation by throwing away the six unused states.

How would one go about doing math operations on a computer? Well, microprocessors are very good and quick at adding or subtracting but clumsy when multiplying or dividing. Early microprocessors required many operations or, so called, clock cycles to produce numerical products and it was common to have a math coprocessor standing by to do the heavy lifting. For example, if you want to multiply a number by 10 in the decimal system you just move the decimal point one position to the right. In the binary system you would shift left (x2), shift left again (x4), shift left again (x8), and then add twice to achieve the 10x product. Clearly, there is a lot of time consuming overhead doing math in this fashion. Contemporary microprocessors are constructed with onboard and dedicated numerical processors with slick routines and which unburden the main unit.

If you look at the schematic of any computer one thing will pop out immediately. There are lots of parallel paths connecting the various semiconductor packages. These parallel wire structures are called busses and might be as wide as 16 bits… possibly more… for memory addressing as an example. There is likely a data buss as well. One line generally represents the buss with breakouts at the ends. Each wire handles one bit of data on the data buss.

In summary, the intent of this presentation is to show that symbols can be used to tally events and that recycling symbols will work in any number system. Starting with the familiar decimal number system and showing that symbol manipulation leads handily to the very simple two state, or binary, number system. A bit is a two state binary digit, a nibble is four associated bits, a byte is 2 associated nibbles or 8 bits, and a word is 2 bytes of 16 associated bits. Modern computers are said to have 32 bit words and, in some cases, 64 bit words.

This concludes the set up discussion for bits, nibbles, bytes, and words. Are there any questions or comments with regard to tonight's discussion topic?

This is N7KC for the Wednesday night Educational Radio Net

Phase Shift Keying, Bob, No. 70

2009-09-23T18:02:00.000-07:00

Tonight I am continuing with my series on Spread Spectrum Radio. I am going to discuss Phase Shift Keying (PSK), which is the form of modulation used by Direct Sequence Spread Spectrum (DSSS) Radio.

Spread Spectrum Radio Review
Let's have a short review of spread spectrum. The two main kinds in use in ham radio are Frequency Hopping and Direct Sequence. Frequency hopping is relatively easy to understand. Your carrier, rather than being on a fixed frequency, jumps from one frequency to another. As long as the equipment receiving makes the same jumps you will be able to transmit the signal and prevent interference on any one frequency from causing a problem. This can be used for analog or digital transmission but is most commonly used for digital. Note that you must have a pattern of frequency changes that is known to both parties in order to allow the receiver to follow the transmission.

In the other method, Direct Sequence, you only transmit digital information. In fact the name "Direct Sequence" comes from the 11 digit sequence of ones and zeros that is used to modulate the carrier. If your data bit is a zero then you send the sequence normally. If your data bit is a one then you send a one where the sequence has a zero and send a zero where the sequence has a one. For example 101 would turn into 010. I mentioned that the carrier is modulated by this sequence but I didn't say how. It is modulated using Phase Shift Keying.

Phase Shift Keying (PSK)
So, what exactly is phase shift keying? It is a way of changing the phase of a carrier to transmit a digital signal. In essence what you are doing with PSK is phase hopping. In the simplest example called Binary Phase Shift Keying (BPSK) you hop 180 degrees out of phase to transmit a certain piece of digital data. So the signal is either in it's "normal" phase or in it's 180 degree out phase which is to say, inverted. Note that the frequency of the carrier isn't changed but when you change the phase and modulate the carrier you create side-band emissions. The faster you modulate the signal, the wider the side-bands. In addition to BPSK there is Quadrature PSK (QPSK) where the phase can be one of four values, 0, 90, 180 or -90. There is also 8PSK using 8 phase angles and so on. The general term is Multiple Phase Shift Keying (MPSK).

Differential Phase Shift Keying (DPSK)
Basic BPSK has the signal at normal 0 phase to represent a digital zero and at 180 degrees out to represent a digital 1. A commonly used variation on this is called Differential Binary Phase Shift Keying (DBPSK) and instead of a 1 being 180 degrees out of phase, a 1 always changes the phase while a 0 always keeps the phase the same. This way you don't need a reference signal to know which is 0 degrees and which is 180 degrees.

PSK-31
If you want a very narrow signal you are limited to a slow digital transfer rate. This is the case with PSK-31. The 31 comes from the 31.25 bits per second data rate which generates 31.25Hz sidebands. This is pretty much the opposite of spread spectrum. The whole point of PSK-31 was to use such a small slice of the band that you could actually fit many PSK-31 channels in the space of a typical SSB voice bandwidth.

PSK for Spread Spectrum
With spread spectrum you want a very wide bandwidth; by definition, one that is much wider than necessary to convey the information. By encoding each bit of data with the 11 bit sequence used in DSSS you now modulate the signal 11 times for each bit transferred. So for a 1 Mbit/sec transmission, you modulate at 11 MHz. This achieves the spread spectrum you are looking for. This modulation is encoded using DBPSK and a suppressed carrier.

THE VACUUM DIODE EXPOSED, Lee Bond N7KC

2009-09-16T19:39:00.000-07:00

September 16, 2009 Educational Radio Net, PSRG 69th Session

What a digital summer we experienced at the hands of Curt Black, WR5J! Curt pulled all the stops on a summers survey of free software downloads for your computer which, more or less, turned your radio into an analytical tool. As impressive as this tour was, one must ultimately realize that the most complex task that your computer performs is based on tiny packets of electrons or "charge" being directed here and there by the software commands. Elemental electrons in motion, or moving electric "charge", is the bottom line idea in electrical theory and all electrical devices including radio equipment.

Let's review what we know about "charge". We know that it enjoys the symbol Q in the literature. We also know that it is an assembly of electrons and can be as few a one electron. We know that a collection of electrons numbering 6.14 x 10^18 is known as a Coulomb of charge. We know that charge will move under the influence of an electric field. We know that the original notion, or conventional notion, of charge was based on the erroneous idea that charge carried a positive sign hence moved in the direction of an applied electric field. Modern theory has reversed the original positive charge idea since electrons are negative entities and, in fact, move counter to the direction of any applied electric field. We know that charge can be motionless as in static charge. We know that an electrical current is charge in motion. It would seem that we know a lot about charge.

The study of charge is best represented by the science of Physics with Physical Chemistry running a close second. The study of charge as it applies to the vacuum tube would come under the heading of Classical Newtonian Physics in contrast to the study of charge in semiconductor materials which would come under the heading of Modern Quantum Physics. In my view the vacuum tube represents the most elegant device for demonstrating the behavior of electrical charge influenced by an electric field. Lucky me to be raised in the heyday of the vacuum tube. As late as 1963 the US Navy destroyer to which I was assigned had a single piece of transmitting equipment that had modern solid state diodes in the circuitry. The selenium rectifier preceded germanium devices and modern silicon devices and required no heater but it is a stretch to include it as more than a rudimentary solid state device. The solid state transistor with all its ramifications is a relative newcomer to the field of electronics. Modern radio equipment's are solid state for the most part and only the old timers can relate stories of warming their hands in the glow of those magnificent glass bottles.

No one has actually seen an electron. These entities are very, very tiny and to image them requires wavelengths small in comparison to the size of an electron. The one common instance of, more or less, stationary electrons occurs in the lattice structure of many crystals and x-ray crystallography has demonstrated diffraction images suggesting that these things are real. The fact that we can manipulate these tiny guys to the degree that we can is testimony to the very clever work of early scientists.

We know that conductors have an abundance of so called "free" electrons. This is in contrast to tightly "bound" electrons which are not available to contribute to electric current flow. For example the neutral copper atom has 29 electrons associated with the nucleus in 4, so called, shells with the innermost shell containing 2 electrons followed by the next shell containing 8 electrons followed by the next shell containing 18 electrons followed by the outermost shell with a single, so called, valence electron. The three inner shells are tightly bound to the atomic nucleus but the outer single electron is easily forced out of place and can contribute to the electric current bumping along a copper wire. Most metals are conductors to varying degrees with silver, copper, and gold at the top. A copper atom missing its valence electron is known as a copper ion.

I think we now have enough information to appreciate how a two terminal vacuum diode works so let's move on to some apparatus to demonstrate the effect. Forget the little glass bottle for the moment. We are going to use a laboratory bell jar and good quality vacuum pump as a part of our apparatus. Everyone has seen the "bell" jar on a stand with a mechanical vacuum pump attached. For our purposes the bell jar stand needs some electrical penetrations so that we can supply potentials to the bell jar innards. The first of the two inside devices is the filament or heater which also serves as a cathode. There are several schemes for heaters so let me select the one known as the directly heated filament cathode. This will be a tungsten wire section which will glow a bright red to orange when filament voltage is applied. Adjacent to the filament-cathode wire we will position a "plate" of flat metal such that it does not touch the filament. This metallic plate is, in fact, called the "plate" electrode in vacuum tube terminology and serves as the anode. Note that the plate may be cylindrical and surround the filament in real world devices.

Our demonstration diode is complete. We have a filament (cathode) and plate (anode) plus a means of producing a good vacuum so on goes the bell jar but someone forgot to start the vacuum pump. Not realizing that a good vacuum is missing we switch on the filament voltage and sure enough the filament starts to light. Then there is a bright flash as the oxygen in the bell jar contributes to the destruction of the filament. Oops. Off with the jar and we install another filament wire. Ok, this time we turn on the pump and let it run until it chortles. Now when we flip the switch for the filament the wire glows a cheery orange. The chortling pump indicates that the internal vacuum (or pressure) is in the 1 to 10 micron range and suitable for our demonstration. The low internal pressure means that atoms of oxygen and nitrogen are scarce and will not interfere with the electronic process that we are interested in observing.

Let's think about the filament voltage for a moment. I did not mention it but the source of the filament voltage is a battery. Traditionally the battery used for filament power is known as the "A" battery.

So, here is our situation... we have a nicely glowing filament with an unconnected plate nearby and both are within a reasonably good vacuum. The glowing filament is probably heated to 800 degrees F or thereabouts and the thermal energy of the filament has caused lightly bound electrons to break free and form a cloud in the immediate vicinity of the filament-cathode. The thermal energy for breakaway is known as the work function and metals vary in this regard. Some substances such as barium offer very low work functions and are used in cooler, indirectly heated, cathode structures.

Our cloud of electrons is negatively charged. If we cause the nearby plate element to become positively charged with respect to the filament-cathode then the electrons will move toward the plate anode and, since moving electrons constitute electrical current, we can measure a plate current if we insert some current measuring device in series with the plate. With regard to the plate, the battery traditionally used to supply plate voltage is known as the "B" battery hence follows the term B+ for the plate positive voltage supply.

There is a third battery associated with vacuum tubes which is known as the "C" battery however it is not relevant here since we are using a two terminal device or diode and the C battery is only relevant in triode structures and beyond for grid biasing.

At this point we have demonstrated that electrons will traverse a vacuum if the plate is positive with respect to the source of electrons. If the plate is negative relative to the source then the electrons are repelled and no plate current will flow. Herein lies the secret of the rectifying diode. If the plate is alternately positive then negative with respect to the cathode as would happen if connected to alternating mains then plate current only flows on positive excursions of plate voltage. Bi-directional current from AC mains becomes unidirectional current in the plate circuit. A single diode offers half wave rectification and a dual diode (or two individual diodes) offers full wave rectification.

The high vacuum in the bell jar or little glass bottle performs two functions. First the pumping process removes virtually all oxygen so the filament suffers no oxidation. Secondly, the high vacuum is synonymous with low pressure both which equate to few residual gas particles present to hinder electron flow from cathode to plate anode. In reality small glass bottles with high internal temperatures will out gas damaging particles which will poison the vacuum so special devices known as "getters" are used internally to trap these vacuum destroyers.
Special attention must be given to the metal leads going through the little glass tube envelopes. If the glass and wire conductors do not expand and contract in the same manner with extreme changes in temperature then the seal will be broken and the tube will be rendered useless in short order. Special wire alloys which match the glass thermal characteristics are used to avoid this problem.

In summary, the physics and mathematics associated with the classic vacuum tube is elegant and a fun pursuit for the very curious. The concept of electronic charge flow within a triode vacuum tube is easily grasped and directly applicable to field effect transistors. The natural extension from diode to triode by introducing a control grid between cathode and plate made possible amplification and the rest is history.

This concludes the set up discussion for the Vacuum Diode. Are there any questions or comments with regard to tonight's discussion topic?

This is N7KC for the Wednesday night Educational Radio Net

Winlink 2000, Boone Barker KC7RK, no. 68

2009-09-09T00:35:00.000-07:00

The Winlink 2000 System: E-Mail by Radio for Radio Amateurs
Boone Barker, KC7RK

Introduction
This paper provides a brief introduction to the Winlink 2000 system—what it is and how it works, and how to become a user.

To start, here are a couple of defining quotes from the Winlink web site at www.winlink.org .

“Winlink 2000 (WL2K) is a worldwide system of volunteer resources supporting e-mail by radio, with non-commercial links to internet e-mail.”

“To use the Winlink 2000 system, you must hold an Amateur Radio license or be a member of a supported organization or agency. Use of the system and all software is free of charge for those who qualify.”

So Winlink is global, with access around the world. It is developed and supported entirely by volunteers. It is free. The system provides e-mail services to licensed Radio Amateurs without access to the internet such as mariners at sea or expeditions in remote areas.

In addition, a growing number of government agencies and organizations have included WL2K in their emergency communication plans. Winlink 2000 can provide user -to-user e-mail services in a familiar format from inside a disaster area, using only a radio to connect to the outside world.

Elements of Winlink 2000
At the heart of the WL2K system are five mirror image, redundant Common Message Server (CMS) hubs. They are located in San Diego (USA), Wein (Austria), Perth (Australia), Halifax (Canada), and Washington DC (USA). With this redundancy, the system will remain operational even if large segments of the internet are down.

Connected to the five CMS sites are a multitude of Radio Message Server (RMS) nodes, like spokes on a wheel. Traffic flows between the CMS hubs and the internet e-mail recipient, and between the end users and the RMS gateways.

As an aside, the term “PMBO” (for a participating mailbox) is being phased out, but still shows up in Winlink writings.

The radio network has both RMS HF stations and RMS VHF/UHF Packet stations.

RMS HF stations form a controlled and frequency-coordinated global network of Winlink stations. The HF stations all use Pactor, a digital ARQ mode that transfers text files and graphics quickly and error-free. Pactor 2 and 3, the faster modes, are only available on TNC’s produced by SCS in Germany. The WL2K Development Team is working on WINMOR, a new HF transmission protocol that will be freely distributed. It will complement, not replace Pactor; RMS HF stations will be able to handle both modes.

RMS VHF/UHF Packet stations are also part of the network, providing automated messaging capability using AX.25 packet radio in combination with the WL2K Common Message Servers. Although limited in range, RMS Packet stations are widely available in the United States and a few other countries. RMS Packet can provide regular local access to Winlink, or a temporary emergency portal for radio e-mail users, or for fixed installation at unattended remote locations where it can provide radio e-mail communications to the “last mile.”

The locations of public and emcomm RMS stations are shown in maps on the Winlink web site. Related status tables list station call sign, with frequency and mode and grid locator. Note that information about frequencies used by RMS HF emcomm stations is limited to authorized sysops and users.

WL2K Client Software
Paclink is a Winlink 2000 radio e-mail client that links to common e-mail programs such as Outlook Express and Mozilla Thunderbird. Paclink adds telnet, VHF packet radio, HF Pactor radio and WINMOR HF radio channels for WL2K connectivity to compatible user e-mail client programs. Installation and configuration are relatively easy.

Airmail is the oldest and most widely used e-mail program for sending and receiving messages on the Winlink system. Airmail supports HF Pactor, VHF/UHF Packet, and telnet connections over any TCP/IP medium including the internet and high-speed radio media like D-Star. Airmail also has position reporting capability, and a very nice HF propagation prediction program. It can be linked to common e-mail programs such as Outlook Express. Installation and configuration are somewhat difficult, but a nice guide is available; just Google “INSTALLATION AND SETUP FOR WINLINK AIRMAIL”.

Airmail is a stand-alone e-mail program. The primary drawback of Airmail is that it only works with a short list of hardware modems. But it is well suited for WL2K HF connections using a Pactor modem. And the latest version of Airmail 3.3.081 can be used with AGW Packet Engine and a soundcard to make VHF/UHF packet connections, by installing AMPE software. See http://www.qsl.net/mararc/ampe.htm web site.

On the other hand, Paclink has to be linked with an e-mail program. But it works with a wide variety of hardware TNC’s and modems and with AGW Packet Engine. TNC initialization scripts can be modified by the user. Also, scripts can be used to connect through a digipeater or packet node. CMS Telnet is simple and easy on Paclink, to send and receive WL2K messages on an internet connection.

Both programs are free to download from the Winlink web site.

Other software
AGW Packet Engine (AGWPE) handles traffic between your TNC or soundcard and packet programs that are configured to use AGWPE. It is free to download from the SV2AGW.com web site. A lengthy tutorial for installation and configuration is located at http://www.kc2rlm.info/soundcardpacket .

Winlink 2000 RMS Packet gateways can also be accessed with regular packet software, to compose and send a message from the keyboard. Just connect to the RMS Packet node and read the greeting. Type H for help and then follow the instructions to compose a message. This is perhaps the easiest way to try out Winlink if you already have a packet setup.

Hardware
For telnet connection to a CMS, the only hardware needed is a computer with internet access. WL2K e-mail through RMS Packet stations requires a VHF radio, a compatible TNC or modem or soundcard, and necessary interface cables.

To connect with an RMS HF gateway on Pactor 1 requires that you have any one of the hardware TNC’s on setup lists in Airmail or Paclink. Pactor 2 or 3 requires that you have a Pactor TNC made by SCS . These cost $1,000 or more.

How do you get started?
First and obviously, you need an amateur radio license. With that, here is a suggested initial sequence.

Go to www.winlink.org, register on the web site, and download Paclink or Airmail—your choice. Install and configure the software for telnet to a CMS site. Compose a test message to your internet e-mail address. Send the message using the telnet connection. When that is successful, reply to your Winlink e-mail address.

Another option: if you already have an operational packet setup, use it to connect to a local RMS Packet node. The Winlink web site has a map that shows all of the active RMS Packet stations. Just zoom in on your local area and pick them out. Then go to the Reports tab on the Winlink Web site, scroll down to RMS Packet Status, and look up frequencies of those stations in the table. Sometimes these local nodes are not functioning. So if you don’t get a connection, try another station.

With your first radio or telnet e-mail you will be registered in the WL2K system. Your e-mail address will be [your call]@winlink.org.

You can use WL2K client software with packet and your TNC if it is listed in the setup for Paclink Packet TNC Channels or in Airmail VHF Packet Client Setup. Check out the TNC using a simple terminal program. Then try connecting to one of the local RMS Packet stations.

If you want to use a soundcard for packet, first download and install AGW Packet Engine. Create a new radioport for your soundcard. Then configure Paclink or Airmail to use AGWPE. Remember that Airmail requires that AMPE be running. There is a link to AGWPE is the Airmail TNC list but it is not functional.

You might also want to download AGWTerninal, and AGWMonitor from the SV2AGW web site. They are free. AGW Monitor lets you see all the traffic to and from your TNC/modem/soundcard, and AGWTerminal is a nice simple terminal program. AGWTracker is a simple APRS program, also nice. All require that AGWPE or Packet Engine Pro be running.

If an online course is to your liking, there is a “Winlink for Dummies” course that takes you through all the steps. It can be accessed through www/winlink.org/GetStarted.

Some recommendations
You should always format WL2K e-mail messages in plain text. HTML format adds unnecessary bytes to the message. Attachments should be made as small as possible.

Learn about the Winlink Whitelist and how to work with it. This is an anti-spam filter. E-mails to your Winlink e-mail address need to have //WL2K in the subject line or they will be rejected—unless they come from an e-mail account on your Whitelist. E-mail addresses on outgoing messages are automatically added to your Whitelist.

When you configure a radioport in AGWPE for SignaLink USB, select an unused printer port (LPT3) as your PTT port. It’s easy to hang up at this point in the setup.

Summary
Winlink 2000 has been used since 1999 by Radio Amateurs at sea and in the jungles to send e-mail messages by radio. As a result of experience in Katrina recovery operations and other disasters, Winlink has been included in operational plans of a growing number of emcomm organizations such as RACES and ARES units, Red Cross, MARS, Baptist Relief, and the Salvation Army.

Another defining quote from the Winlink web site:

“The WL2K mission is to provide, through a volunteer network, effective last resort communications in civil emergencies and personal communications in non-emergency conditions.”

As a Radio Amateur, you may already have experience with packet radio—that’s all you need to access Winlink by radio. Another simple start involves connecting by telnet over the internet. And if you are already a Winlink user, you might consider becoming the sysop for your own RMS Packet station. Software and guidelines are on the web site.

So have fun setting up Winlink and trying it out. It might well be very useful in an emergency, to you and to your community.

September 9, 2009

Spread Spectrum Communications, Bob, no. 67

2009-09-01T22:58:00.000-07:00

Tonight's topic, spread spectrum communications, may seem to be the stuff of spy fiction and ultra-expensive military hardware, but you have almost certainly used spread spectrum whether you know it or not and you probably have the sophisticated spread spectrum radio gear right in your own house. I'm talking about wireless networking gear, also known as WiFi. More on that later.

WHAT IS SPREAD SPECTRUM?
According to the ARRL Handbook, spread spectrum is defined as using an RF bandwidth much larger than needed to carry the signal, and where the bandwidth of the signal is independent of the modulation by the signal. It is a form of radio transmission that makes use of a wide bandwidth to avoid interference by noise or other signals. You can imagine that if you are transmitting a simple AM signal over 100 frequencies at the same time then someone transmititng on any one of those frequencies will only contribute one percent toward the final recombined signal. This would be fine until you had someone else also transmitting an AM signal on the same 100 frequencies. Then you would be back to a big interference problem. Partly in order to allow hams to use the same frequency range, there are more sophisticated ways to use those multiple frequencies. We will discuss those in a moment.

SPREAD SPECTRUM TRADE-OFFS
In general, spread spectrum transmissions offer three big advantages:

Relative Immunity to Interference
As described above, unless someone else is using the very same spread spectrum technique and is synchronized with you, you likely won't notice the interference
Security
As we will see, there are sophisticated ways to encrypt a signal. This is why it is still valuable to the military.
Lower Power Density
By spreading the signal over a range of frequencies, the power at any given frequency is so low it can be below the noise floor and unnoticed.

There is only one real trade-off and that is the technical complexity necessary to accomplish spread spectrum.

HISTORY OF SPREAD SPECTRUM
In a sense you could say that spread spectrum began with the earliest radio transmitters. Spark gap transmitters created CW signals that covered a very broad spectrum. You could charitably say that this signal could get through interfering signals but really, it was more of an interfering signal.

Early experiments with intentional spread spectrum began in the late 20's but it was World War II and the military that really pushed the technology forward. Unfortunately, because spread spectrum is still used by the military, much of the history is still kept secret.

SPREAD SPECTRUM IN HAM RADIO
In 1981, a group called the Amateur Radio Research and Development Corporation (AMRAD) began experimentation with spread spectrum. In 1989 an idea was put forth to use the Wireless LAN (WLAN) devices in ham radio, and in 1999 the FCC relaxed their rules about hams using spread spectrum. This relaxation opened the door for hams to use equipment already being made for WLAN.

Analog signals can be carried over spread spectrum transmissions, but nearly all spread spectrum use today is with digital signals and that is what we will discuss.

COMMON TYPES
Frequency Hopping Spread Spectrum (FHSS)
As the name implies, the transmitting frequency hops around in a pre-arranged pattern. In the 802.11 spec, there are 3 sets of 26 such patterns using 75 frequencies. By some clever hopping algorithms you can have 802.11 devices using different sequences, or channels, on the same 75 frequencies without interfering with each other. Because there are only 78 sequences, a receiving device could discover the channel being used by the various transmitters and sync up with one.

Direct-Sequence Spread Spectrum (DSSS)
In this method, a pseudo-random code is used to modulate the signal and drive a phase modulator using phase shift keying. I have to admit this it getting into the fringes of what I know so I am going to leave it at that.
Note that by using a pseudo-random code that is not generally known it would be possible to securely encrypt a signal with DSSS. Of course we are not allowed to do that in amateur radio and we avoid that pitfall by using published codes as can be found on the ARRL web site.

Orthogonal Frequency Division Modulation (OFDM)
This method is more like what you may think when you think of spread spectrum. In this mode, the signal is transmitted on 52 carrier frequencies simultaneously. Four of these are called pilot carriers and they help provide the synchronization. The other 48 each transmit independent bit streams so at any given time, 48 bits are being transmitted at once. The reason it is called orthogonal is that the frequencies and modulation patterns are chosen so that each frequency falls in the null of the neighboring frequencies.

THE FUTURE
Since this mode is so new and underutilized in ham radio, I'm going to do something I don't normally do and that is predict the future of spread spectrum. It is here to stay until something better comes along and, though it may not happen, I wouldn't be surprised to see it adopted in the low bands eventually. I know some of the new digital modes use it to some degree and I can see the FCC, being the pragmatists they are, expanding the use of it as the technology allows.

I want to acknowledge two primary sources for tonights lesson. The ARRL Handbook, a wealth of all things Ham; and Spread Spectrum Scene which I barely scratched the surface of.

Reminder - Educational Radio Net Wednesday night 8:00pm and Last Summer of Digital Fun Post

2009-08-25T22:29:00.000-07:00

Reminder - Educational Radio Net Wednesday night 8:00pm PSRG 146.96

For the new folks on this WA-DIGITAL list, the Summer of Digital Fun Series
finishes up this Wednesday on the PSRG machine, 146.96 (-600 kHz offset, 103.5
tone)in Seattle.

All are welcome.

Make no mistake, the Educational Radio Nets will continue and the Digital Series
will also continue, but for things digital, probably once or so per month as we
keep exercising with these amazing modes.

I was tempted to talk about the Automatic Position Reporting System, APRS - a
tasty flavor of packet radio. Just eavesdrop on 144.39 for a sense of how
popular this mode is. However, it seems the last couple of weeks have seriously
challenged the group which has been winnowed down to just a few players. I hope
folks will pursue APRS on their own or contact me off list for any help they
might need with that system - it is really a blast. For lots of help including
a well developed Elmering program, check out http://www.nwaprs.info/ or just
look at the cool maps at http://aprs.fi/

So, for this last Summer Session we'll have more digital fun with a recap of
what we've done through the summer. Please begin the net with FLDIGI up and
running with acoustic coupling between your radio and the computer.

The best way to enjoy the Educational Radio Net is to have your software set up
and running as the net starts at 8:00.

If you have an interface, hook it up to your two-meter rig, otherwise use
acoustic coupling with a microphone feeding shack audio into your computer and
the rig audio softly coming out of a speaker in the room with you fairly close
to the mic.

If this is your first session, no problem. Pull the software off the WA-DIGITAL
files section and install it. Tune in and we'll go over set up of the software
during the session. The software is on the WA-DIGITAL yahoo group. If you are
using VISTA, please load the version FLDIGI 3.11.4-WinV. When the update went
to 3.12.4 for all windows systems, something bad happened, and VISTA stopped
working. There are Linux and Mac versions of the software as well - just Google
NBEMS or go to http://www.w1hkj.com/ .

Posts 2 and 3 go into setting up for FLDIGI. The first part of Post #4
describes the set up for acoustic coupling. IF you are set up for acoustic
coupling, you should see a difference in the waterfall as you open and close the
squelch on the rig you are using to monitor the PSRG machine. If you don't, go
to the CONFIGURATION menu and the AUDIO tab, then devices to point the software
to the audio source.

We will start out tonight with a blast of MT-63 preceded with an RS-ID to
automatically switch your software to the correct mode and frequency, so get
ready to receive on the output of the PSRG machine, 146.96. Remember to setup
FLDIGI with menu item CONFIGURATION, then under the ID tab to check the box next
to "TRANSMIT MODE RSID" and "RSID SEARCHES ENTIRE PASSBAND" Finally on the main
receive screen, be sure and check the little box up in the upper right corner of
the screen labeled "RS-ID" so that a green light is visible indicating you are
ready to switch modes and frequency when the signal is received. This feature
has to be turned on each time you want to use it - mostly to keep from being
wrenched out of an ongoing QSO by receiving another RS-ID.

If you have trouble with copy during the net, you might check the input of the
repeater to see if that is better for you. Several folks sent messages last week
suggesting that.

See you on the Net.

Hopefully this will be just the beginning of some great digital adventures.

I would like to suggest we continue using the WA-DIGITAL mail reflector to
schedule digital QSOs with other folks, also don't forget
http://www.obriensweb.com/sked/ to set up SKEDS or WSPRNET.ORG to monitor your
received whisperings.

Also, please consider joining the Pennsylvania NBEMS group via Echolink on a
local repeater or in the privacy of your home computer. The Pittsburgh hams have
been having a net using about 50% voice and 50% MT-63. We may join them by
Echolink by connecting to W3YJ-R (node 177325) at 5:00pm Sunday evenings (8:00pm
Eastern Time).

After the 5:00pm net I would like to suggest we retire to the SEA machine on
145.010 simplex. (just "Connect SEA" and then type "TALK" to join the group and
//ex to leave (the instructions come up when you join.)

As the fall comes on, I would like to suggest we dive into some of the major
pieces of software available and checkout all that they are capable of - I'm
thinking of MULTIPSK which does way more than just PSK, and HAM RADIO DELUXE -
HRD with D780 for digital modes - a beautiful piece of software.

Our continuing thanks to the PSRG for the use of the repeater for this net and
so many others that enhance our radio community.

vy 73 de WR5J

Curt Black
black@nwfirst.com

As a reminder, here is what we covered this summer:

Blog Post - #1 Intro to Digital Communication, Software and Modes Wednesday,
June 3, 2009

Blog Post - #2 Intro to FLDIGI – Install, Setup and Mode Selection, Wednesday,
June 10, 2009

Blog Post - #3 Using FLDIGI – Starting with PSK-31 and Transmitting a Good
Signal Wednesday, June 24

Blog Post - #4 More FLDIGI – RTTY, the WRAP Utility and RS-ID, Wednesday July 1,
2009

Blog Post - #5 WSPR – Weak Signal Propagation Reporter, Wednesday July 8, 2009

Blog Post - #6 MMSSTV/EasyPAL, Slow Scan Image Transmission, Wednesday July 15,
2009

Blog Post - #7 Digital SSTV (week 2) EasyPAL, Wednesday July 22, 2009

Blog Post - #8 WSJT-JT65A – Terrestrial HF, Wednesday July 29, 2009

Blog Post - #9 WSJT-HS-Meteor Scatter, Wednesday August 5, 2009

Blog Post - #10 Packet Radio Using Flex32, Wednesday August 12, 2009

Blog Post - #11 Packet Radio Using AGW Packet Engine, Wednesday August 19,
2009

Blog Post - #12 WINDRM – Digital Voice and HRD/DM780, Wednesday August 26, 2009

OK - we didn't really do WINDRM - take a look at the blog post and you will see
why - we still might give it a try, but it is the same modulation approach used
by EasyPAL and that didn't fly very far through the PSRG machine - However, we
did very well with an after-net on the 444.550 WW7SEA machine - as in perfect
copy and 22dB S/N ratios. We've got to find out what that is about...

Blog-Post-12 – WinDRM—Digital Data and Voice Using Digital Radio Mondiale

2009-08-25T13:09:00.000-07:00

Blog Post 12 – WinDRM—Digital Data and Voice Using Digital Radio Mondiale on the Han Bands

Wednesday August 26, 2009

This is Curt Black, WR5J, with the Educational Radio Net –

Please standby for a WinDRM Digital QST

OK, we are out of time for the Summer of Digital Fun, but I had prepared some material for this mode, so here is what I have so far.

The problem with these digital voice modes is the loss of the use of a proprietary codec - here is a recent message from Mel Whitten:

Curt,

The MELP codec is no longer available because it was brought to

The attention of one of the IP holders that we were using it. I

don't think the IP holder would really "care" because of the way

we were using MELP, but when confronted by this "person" in writing..

then the IP holder had to defend his property. Thus, we are left

with LPC-10, which does not sound "too bad" and could be used to

demonstrate capability.

… 14.236 is calling/net freq for digital voice. Some stations may be

heard around noon central time. Nets are still run (summer time thy're

not as frequent) on Sat and Sun on the times given on the web site.

keep in mind, that you may find FDMDV, AOR's DV and WinDRM on these frequencies. FDMDV suffered the most from the loss of MELP and does not sound very good with the lower bit rate LPC-10 but it has "instant" sync and simple to use. With MELP, FDMDV was a real winner. Work continues to find a replacement, but this is very difficult. There are no "legal" problems with any DV using MELP or SPEEX codecs. They are both open source. DV is about dead and probably will remain that way until a MELP equivalent codec is found or some new technology is found. AOR's DV is not robust enough to cope with current poor band conditions do to low sun spot activity. It does work very good with at least S9 signals and no QRM. Excellent voice quality but so -was- WinDRM with MELP.

Channelization for DV would be optimum. QRM is a real problem from SSB. FCC rules say DV must operate in the Voice sub-bands. . .

<<>>

The software is on the Yahoo WA-DIGITAL files section http://groups.yahoo.com/group/wa-digital/files/

It sounds like the loss of the Codec may have delt a fatal blow – but here is the installation and use information for those who might want to experiment – 73 de WR5J

http://n1su.com/windrm/download.html

WinDRM Docs – Release 1.3 was developed by Cesco, HB9TLK from a relatively new broadcast standard called Digital Radio Mondiale (DRM) and it’s open source

encoder/decoder named Dream (http://drm.sourceforge.net/). DRM is based on a proven

data communications technology called Coded Orthogonal Frequency Division

Multiplexing (COFDM) with Quadrature Amplitude Modulation (QAM). COFDM uses

many parallel narrow band sub-carriers instead of just one single wide band carrier for

transporting the data. As a result, WinDRM provides an efficient and robust method to

exchange information over HF including Digital Voice using open source CODECs.

WinDRM utilizes Forward Error Correction (FEC) and an Automatic-Repeat-Request

(ARQ) mode to ensure error free data transfers. WinDRM runs efficiently under

Windows operating system 2000 and XP. No modifications are required for modern SSB

HF ham transceivers. Current releases of WinDRM software may be found at

www.n1su.com/windrm. Other digital HF data/picture transfer software such as Digtrx,

EasyPal and HamPAL share the same core ham-DRM standard and therefore are

compatible with WinDRM. WinDRM is not compatible with all newer encoding methods

now being used by HamPal. WinDRM is not compatible with AOR’s ARD 9000/9800

fast radio modem.

The WinDRM GUI (graphic user interface)

Five “State” Radio Buttons - (enabled under program control during receive ) as follows:

Input/Output

IO – Enabled: Sound card is linked and passing data to the processor. Disabled:

Indicates sound card is not compatible and/or PC’s processor is too slow. If not enabled,

WinDRM

WinDRM will not decode data. Note: IO should always be enabled during receive and

transmit.

Frequency Acquisition

Freq – Enabled: The three FAC reference carriers/pilots (3 higher intensity vertical lines

in the waterfall displays) have been found. These correlate with the DC Offset frequency

(normally 350Hz) which is graphically shown as a blue vertical line.

Time Synchronization Acquisition

Time – Enabled: Timing acquisition is done. This indicates the search for the beginning

of the OFDM symbol has been completed. Disabled: No synchronization, (usually

caused by poor SNR) distortion of the transmitted signal and/or receive band pass is too

narrow. Note: False indications (flickering) can be caused by AWGN (atmospheric

noise) and generally, may be ignored.

Frame Synchronization

Frame - Enabled: Frame synchronization is completed and the start of a DRM frame

(400ms) has been found. The Receiver is in synchronization with the transmitting station.

Disabled: Lost frequency synchronization due to poor SNR or change in frequency (avoid

“tuning” once in sync). Note: False indications (flickering) can be caused by AWGN

(atmospheric noise) and generally, may be ignored.

Fast Access Channel

FAC – Enabled: Receiver is in the tracking mode, has received a good Cyclic

Redundancy Check (8-bit CRC) and is in synchronization with the WinDRM transmitting

station. FAC is a separate logical channel and modulated with 4-Amplitude Quadrature

Modulation (4QAM). FAC provides bandwidth spectrum occupancy (2.3/2.5khz), call

sign and other DRM transmit parameters for the WinDRM receiver. Time, Frame and

FAC always precede (must be enabled) MSC channel data. Disabled: Caused by lost

sync, failed CRC, QRM, change in frequency and/or distortion of the transmitted signal.

FAC provides the data for the receiving WinDRM station to set it up to automatically

receive data for file transfer or digital voice (no intervention required by the receive end

operator).

Main Service Channel

MSC - Enabled: Indicates actual audio and data bits are being decoded for voice, text

message and/or images. MSC may be modulated using 4QAM, 16QAM or 64QAM (see

DRM TX settings). 4QAM is unique to WinDRM (DRM uses 16 and 64QAM in the

MSC). The larger the QAM rate the higher spectral efficiency but with lower

performance (less robust in presence of errors caused by poor propagation or

QRM/QRN). Robustness is improved through interleaving of the MSC symbols. This

provides time diversity so that a burst of errors is spread across up to several frames

minimizing the destructive effects on the received data. Like FAC, MSC enabled

indicates the Cyclic Redundancy Check (CRC) has been acknowledged and good data

has been received (Info’s data for MSC will increment after the CRC has been

computed). Disabled: Disruptions (dropouts), text message not received, or missed

block/segment/packet image data. QRM/QSB/QRN and weak signals can cause MSC to

fail or “flicker” during reception. A minimum SNR of 7dB generally ensures MSC will

remain enabled. Note: All these radio buttons must be enabled (from decoded

transmitted data) before the file/picture or voice data will be received.

Files: (download from: www.n1su.com/windrm/ )

The .wav files must be created using Digtrx or similar program. For docs on how to

create these files, go to http://www.kiva.net/~djones/index.htm . Note: These wave files

are not necessary to execute/use WinDRM. WinDRM stores files/pictures with errors in

the Corrupt folder. Good, error free Files/pictures are stored in the Pictures folder.

Mixer.bin contains data for the sound card’s mixer settings. Settings.txt file stores user

settings such as com port, call sign, etc. User files/pictures to be sent may be stored in

any directory for transmission, but are normally kept in the WinDRM directory for quick

access. Note: Digtrx creates 16bit 8000Hz sample rate wave files. WinDRM requires

16 bit 48000Hz wave file format. Use a freeware program like Audacity

(http://audacity.sourceforge.net/) to convert the wave files from 8000Hz to 48000Hz

mono.

Other files are created by WinDRM include:

bsr.bin

bsr0.bin

bsrreq.bin

bsrreq0.bin

RX_Log.txt

Known specs and definitions:

TX Data rate

MSC transmit data rate in bits-per-second (bps) is shown in the SNR box when

transmitting. For the DRM TX “Default” setting this is 2617bps. The Mode box will

display B/S/16/0/2.5 for this setting (see “Mode” for explanation of this data). The

CODECs (Linear Predictive Coding, SPEEX and Mixed-Excitation Linear Predictive)

require at least 2400bps. For data, WinDRM offers a “Speed” mode at a higher bit rate

of 4362bps and a “Robust” slower bit rate mode of 997bps. By changing these DRM TX

settings, the MSC protection, Coding, Bandwidth, and Interleave may be carefully chosen

to match the transceiver filters and current band conditions. For HF, a good starting point

is the default TX DRM setting. For poor band conditions, try the robust mode. Refer to

the specs found at: http://www.qslnet.de/member/hb9tlk/drm_h.html

Modulation and Forward Error Correction

Carriers are modulated using 4QAM, 16 or 64 in the MSC. The QAM constellation size

is selected by the user under the DRM TX settings. QAM4 is set by WinDRM for FAC

since it is the most robust. OFDM/QAM modulated carriers would appear to be

overlapping within their spectrum. However, once they are synchronized at the receiver,

they no longer over lap (now orthogonal/unique) and can then be demodulated. QAM

has both fixed amplitude and phase modulation. Forward Error Protection (FEC) is

provided by Reed Solomon (RS) code. By definition, RS has the ability “…to produce at

the sender ‘n’ blocks of encoded data from ‘k’ blocks of source data in such a way that

any subset of k encoded blocks suffices at the receiver to reconstruct the source data.”

This gives DRM the ability to “repair itself on the fly” by accurately rebuilding the audio

or file data as it was originally coded at the transmitter. If this can’t be done, then

WinDRM keeps track of the errors (bad data segments) in the file and with the BSR, the

data can be replaced with error free data using either the manual request (user

intervention required) or automated using the ARQ feature in a point to point QSO.

PC requirements

Windows OS, 2000 or XP. 700mHz minimum processor speed with 1.2GHz or higher to

ensure smooth operation. Avoid executing other programs while WinDRM is decoding or

transmitting. For testing/experimenting, 2+ GHz PCs can run two instances (i.e. A to B)

of WinDRM in a back-to-back mode (connect sound card line out/speaker to line in/mic

and carefully set levels or use Virtual Audio Cables VAC. Instance A may then be used

to transmit pictures to instance B. If VAC is available (a separate program), DV may

also be demonstrated since VAC take care of exchanging data between each instance of

WinDRM allowing microphone voice input to the sound card.

Status of received data in the Info box for images (RX Pics)

The “Info” box during receive provides a status of the data being decoded as it is

received. These counters are shown in three sets of one to three digits separated with a

forward slash (/). The first set is the number of memory segments (size) in the file. The

second set shows the number of good segments decoded. The last set shows the segment

number of the last segment decoded.

The first set of numbers represents what WinDRM “knows about” at the start of the

transmission and will change because the program begins assembling the data before the

total is known. If a segment is received in error (CRC failure), a following instance

provides the opportunity to receive it again. If received OK, the counter will increment.

After all the data is received, the segment counts will all agree indicating the file has been

received error free. If a picture was received, it will open up in Irfanview or the

viewer/program associated with the file’s extension. Note: The segment size increases

with the constellation size (4 thru 64) of the QAM since it is possible to transmit more

bits per symbol in the higher order constellations.

Status of received data in the Info box for voice (RX)

While receiving voice, the Info block displays 1 to 100% representing the quality of the

decoded data. The quality is determined by the number of good frames of data received

*versus bad since the last synchronization. Drop outs (speech loss) may be experienced

with 70 percent or less. With SNRs of 12 or higher, expect a quality number near 100

percent (no dropouts).

Status of transmitted data in the Info box for files ( TX Pics)

After transmitting the lead in sync data, the Info box provides the status of the file as it is

being sent. The counter consists of two sets of numbers separated by a forward slash (/).

First set shows the instance being sent while the second set shows the percentage (1 to

100 percent) of the total segments sent. The number of instances the file will be sent is

shown in the “Select File” window. A choice of 1 to 3 may be selected but additional

instances can be sent by adding the file in the Select File window more than once.

Status of transmitted data in the Info box for voice (TX)

No data is shown in the Info box during voice transmission except during the lead in sync

period.

Info box during “lead in” transmission

In both picture and voice transmissions, lead in sync data is sent to the receiving station

for setting up the timing and other OFDM carrier information. This lead in maybe

lengthened to provide more set up (sync) time at the receive end by selecting long lead in

under the Select Files window. While the lead in is being sent (up to several seconds),

the Info box will increment various numbers indicating this data is being transmitted and

the actual file data has not started. Some of this data includes determining the size of the

file and packetizing data prior to be sent.

Text Message data

Up to 128 ASCII characters (including spacing) may be transmitted. Greater than 128

will be truncated at the receive window. Text messages may not be sent with data

(file/picture transmissions). Text messages may be added or changed during TX. The

data rate is only 80bps, but the message is continuously transmitted during the voice

transmission. In receive, the text message window remains open at the end of the

transmission. This message window may be closed at any time but will re-open while

data is being received. Text messages may only be sent and received with Digital Voice

transmissions.

Transmit and Receive parameters (and transceiver setup)

For optimum performance, the OFDM carriers must fit within the band pass of the

receiver and transmitter. The default 350 Hz DC Offset was chosen to ensure the 2.5Khz

wide OFDM signal is inside both the transmit and receive audio band pass. The 350Hz is

an offset from DC (0 hertz) and where the carriers of the OFDM begin. The timing

(OFDM searches for this) locks on and starts all it’s shifting up in frequency from the DC

offset for all 57 carriers. This offset can be changed but it must chosen so the spectrum

will fit within the TX and RX band passes. If the DC is moved too much from 350, all

the OFDM carriers may not fit within these band passes. Although it is not important to

be exactly on the transmitting stations frequency, modern transceivers should allow the

receiving station to be within 100hz of this offset frequency. Too far off frequency may

result in lowering SNR if OFDM carriers fall outside the receiver’s band pass. If any

tuning of the frequency is made during receive, the signal is phase shifted and attenuated.

The orthogonality of the OFDM symbols may also be destroyed and this causes ICI

(inter-carrier-interference). This will immediately stop decoding data. Click on “Reset”

to re-sync the data if any tuning must be done to bring all carriers within the band pass of

the receiver. When the WinDRM users talk on SSB, carefully tune to their SSB

frequency. This will ensure you are on the frequency being used for DRM data also. Be

sure the receiver’s band pass is at least set to at least 2.5 kHz FLAT band pass with no

DSP and/or audio processing. For most receivers, setting AGC to Fast (or OFF) will

improve SNR. For transmit, minimize distortion by turning off compression, EQ (or DSP

filtering within the band pass) and avoid any ALC action. For 100 watt rigs, set power to

approximately 15 watts average power. This mode works best with very linear

transmitters and amplifiers. All commercial DRM transmitters are Class A. OFDM has a

rather high crest factor caused by the mathematical FFT operation applied to the

transmitted signal. The peak power is much higher (7-9 dB) than the average power read

on a conventional wattmeter. Experience has found that operating out of the linear region

of your transceiver and/or amplifier may result in a 3 to 4 dB lower SNR at the receiving

station. For a detailed explanation of how to set the power out of your transmitter, go to:

http://www.tima.com/~djones/DRM_power.htm WinDRM’s Shifted Power Spectrum

Density (Shifted PSD) in the absence of multi-path/QRM, will display a “Flat top” signal

across the entire bandwidth of the received signal. Ask the receiving station to comment

on your transmitted signal using this display. If it is not “flat”, then either the transmitter

or the receiving station’s is not set up properly which can degrade performance.

CODEC

Select under DRM TX Settings, “CODEC” (voice) or “DATA” (files/pics) being

transmitted will be displayed. Under program control (FAC data), the receiving station

will automatically decode and display the mode of transmission being sent (LPC,

SPEEX, or Data).

SNR

Signal-to-Noise-Ratio is an estimated value that indicates the quality and strength of the

received signal. Experience has found, near error free data may be decoded with a SNR

greater than 7.0 dB. The higher the number, the better the signal is being received. An

SNR of 10 or better usually ensures error free copy. QRN, QRM, transmit distortion and

propagation problems caused by multi-path cancellation lower the SNR. Transmitters

and amplifiers operating out of their linear region (trying to run too much power!), failure

to turn off compression or DSP/EQ and too narrow band pass all degrade SNR. Under

ideal band conditions, SNR will rise to 25db or greater when both the transmitting and

receiving stations are set up properly. Note: SNR is determined from the carriers

between the low (725Hz) and high (1850Hz) reference pilot carriers only.

Refers to the frequency offset from 0 Hz to the start of OFDM carriers. Default is set at

350Hz. This is an arbitrary number chosen to ensure both the 2.3 and 2.5 kHz signal BW

“fits” within the bandpass of the receiving station. This may be confirmed by observing

the shifted PSD, transfer function displays or the moving waterfall displays. The accuracy

of the receiving station’s tuning for the COFDM signal is dependent upon this factor

which will allow a 100-125Hz tuning error without affecting the decoding process. It is

important to note however, that once sync is obtained, no further “tuning” of the signal

should be attempted. A blue vertical line indicates the location of DC offset. Values of 50

to 5000 Hz are valid entries but 350 Hz is normally used.

Mode

Displays the DRM TX settings. The default is:

B (DRM Mode B) S (Short Interleave) 16 (Main Service Channel 16 Quadrature

Amplitude Modulation) 0 (Protection level) 2.5 (2.5 kHz Bandwidth). Most stations

use 2.5kHz since additional carriers are available with this wider BW giving better

receive performance. TX DRM modes are selected to correlate with the quality of the

signal (as affected by propagation, signal strength, QRN, etc) available at the receive end.

These modes affect the transmission speed and robustness of the received signal. For

more info, see “DRM TX Settings” later in this doc.

Setup

PTT Port

Any com port 1 through 8 may be selected for control of the transmitter’s PTT using

conventional RS232C data terminal ready (DTR) line. For most applications, a standard

RS232C cable is used to connect the PC’s com port to the sound card interface

(RigBlaster or equivalent). In addition, the DTR or ready to send (RTS) line may be

used to mute the receiver’s speaker while receiving data. Implementation of this feature

may be found at KB4YZ’s web site. (http://www.kiva.net/~djones/index.htm ) WinDRM

may be started and the PTT controlled in the “Remote” (PTT on CTS or PTT on DSR)

mode using the com port’s CTS or DSR line. This Remote mode will allow the use of

external switching from the PTT switch on a microphone or a PTT foot switch. To avoid

a possible ground loop, an optical isolator or a relay should be used to assert (apply a

positive +5 to 12vdc) to either the DSR or CTS line. Note: Due to some ambiguity

between Windows OS and WinDRM, the CTS and DSR are reversed (CTS is pin 6 and

DSR is pin 8 in the 9 pin Sub-D PC’s com port connector). Use of a pull-down resistor

on these pins will help ensure no false PTTs. For com port protection, a current-limiting

resistor may be used in series with the positive voltage applied to the DSR or CTS pin.

This Remote feature is not saved in WinDRM’s user’s settings file therefore when used,

it must be checked each time the program is executed. TX voice may also be activated

using the keyboard’s spacebar. With “TX Voice” in focus (as show in above display),

taping the spacebar will put WinDRM in transmit (activating PTT) and pushing it again

will return WinDRM to receive (a toggle function). To un-focus TX voice and avoid

placing WinDRM in transmit while using the keyboard for other functions, push the

keyboard’s “Tab” key. Spacebar PTT will not function while in the “Remote” mode.

Setup

Call sign

Up to 8 number/letters may be entered. “NOCALL” is the default.

Setup

Display

Receive Spectrum

The Spectrum’s display is approximately 2.5 kHz wide in the horizontal while the

vertical shows the amplitude in dB (no scales are shown for any of the displays). The

shape of the signal is rectangular (flat top) and represents the 2.3 or 2.5 KHz band width

of the received signal. This display may be used to set the audio input level of the sound

card. Too much input will over-drive the sound card (line input should always be used

when available) and may cause distortion and low SNR. Carefully adjust the line input

level and the receiver audio until the top of the COFDM spectrum averages

approximately half way up in the display window. Although there is normally good

dynamic range in most sound cards, the goal is obtain the highest SNR reading. After

sync has been obtained, a blue vertical line will appear in the spectrum. This blue line

shows where the timing for acquiring the COFDM signal has started (the DC offset

frequency) which is normally 350Hz. This line may pop up intermittently as it will

“false” on random noise and should be ignored when no valid COFDM signal is being

received. The three reference pilot carriers are easily seen in the display with frequencies

of 725, 1475 and 1850Hz.

Receive Waterfalls

Three waterfalls are available, Moving, Static, and Flicker reduced. The COFDM

spectrum will be displayed with an even intensity level across its 2.3 or 2.5 KHz

bandwidth. Within the waterfall, three FAC reference (or pilot carriers) of higher

intensity can be seen. These stand out because they have higher gain (transmitted at

twice the power). These FAC pilots are modulated with known fixed phases and

amplitude which optimize DRM’s performance for initial synchronization, duration and

reliability. They are used to calculate the initial coarse frequency offset of the received

DRM signal. This is the first part of the COFDM sync process and must occur before the

received DRM signal can be decoded. The high-lighted red markers at the top of the

waterfall display indicate where the FAC reference carriers are located when the

transmitter and receiver DC offsets match. The moving waterfall sweeps from top to

bottom with the red marker’s indicating the position of reference carriers remaining fixed

at the top of the display. The moving waterfall adds a visual method to monitor the

health of the decoded signal in the form of a vertical line on each side of the waterfall

spectrum. During the decoding process, the green vertical lines indicate data is being

received without errors and red lines indicate errors. These green/red indicators move

with the spectrum instantly showing when and where the data errors occurred. The

horizontal line across the top of this display indicates the bandwidth of the COFDM

signal. The signal in the waterfall should fully extend the width of this line. The Flicker

reduced waterfall is a modified moving waterfall designed to reduce “flicker” from some

types of fast LCD or laptop displays. Note: The waterfall display shown above depicts

the effects of multi-path cancellation as shown by the darkened (“notches”) areas. The

carriers in this area are being attenuated due to these phenomena. The two bright lines (on

the bottom left, just before the start of data) is unwanted noise (probably caused by a

ground loop between the transceiver and the PC soundcard) on the Speaker Out audio

line to the transceiver’s Mic input. Every effort should be made to eliminate this type of

interference when connecting audio cables between the PC and the transceiver. To

minimize ground loop and/or RFI problems associated with sound cards and the

transceiver, refer to these informative papers found at:

http://audiosystemsgroup.com/SAC0305Ferrites.pdf

and http://audiosystemsgroup.com/Ferrites-Ham.pdf

Important: It can not be emphasized enough that common mode noise (i.e. ground

loops – ac currents) must be eliminated or risk the high probability that unwanted noise

will be heard in the speaker at the receiving station while decoding digital voice. When

this noise is present, it is directly proportional to the TX microphone (mixer) level input

and will reduce the favorable experience expected of this mode. Only the decoded voice

should be heard from the PC speakers.

Input Level (receive)

This display graphically shows the received audio. Sound card (recording) Line Input

may be set to approximate the level as shown in the display above.

Shifted PSD (receive)

This display plots the “estimated Power Spectrum Density (PSD) of the input signal”.

The X axis measures the PSD of 0 to 50dB while the Y axis is frequency from 0 to 12

KHz. Here the incoming DC frequency (350 Hz) is mixed with 5650 Hz to give a 6 KHz

(the blue vertical line is correctly shown in DRM mode B only). The peak on the left is

the mirror image (5650 – 350 = 5300 Hz) and is partially suppressed by the WinDRM’s

internal IF filter. If a peak is displayed between the signal and the mirror signal, a

50/60Hz noise could be in the transmitted audio from ground loop. The three peaks seen

at the top of the waveform are the pilot carriers for sync and have twice the power. Any

roll off or dips in the waveform indicate the carriers in these areas have a loss of power

caused by QSB and/or attenuation in the band pass of the transmitter or receiver. If the

transmitter or receiver does not allow the 2.3/2.5khz wide (350 to 2850Hz) DRM signal

to pass without attenuation, this waveform will roll off on either end. Up to 10dB or

more SNR can be lost because careful attention has not been taken to properly set up the

transmitter, receiver and soundcard for the “flat top” OFDM spectrum.

Transfer Function ( receive)

This plot shows the “squared magnitude of the channel estimation at each sub carrier”.

The green line is the transfer function (TF in dB) while the blue line shows the phase

distortion of the channel (Group Delay in ms). Optimum signals will yield a flat response

and display even/flat lines across the width of the display.

Impulse Response (receive)

This plot shows the “estimated Impulse Response (IR) of the channel based on the

channel estimation”. This pulse is used in determining the HF channel’s frequency and

phase characteristics so the signal may be restored as close as possible to what it looks

like at the transmitter. The time delay of the shortest path is taken as the zero reference

for the estimated pulse response.

Fast Access Channel (FAC) Phase (receive)

This plot shows the 4 QAM rectangular constellation. For more info on QAM see above

info under FAC radio button and this URL:

http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation

Main Service Channel (MSC) (receive)

This plot shows the various constellations for a 4 through 64 QAM logical channel that

provides the voice and file data. High SNR keeps the points in a close (tight)

constellation but some scattering is expected on HF where the Reed-Solomon error

correction coding is applied. QAM varies the amplitude and phase of each one of the

carriers (for 16 QAM and up). Then, through frequency multiplexing (adding these

carriers together across the 2.3/2.5 kHz BW) the OFDM is created. 16QAM is shown

here.

Setup

CODEC

Either Linear Predictive Coding (LPC) or SPEEX open source CODECs may be selected

for digital voice. LPC is the default. All three require 2.5 kHz/2400bps minimum data

(default DRM TX settings provide this for the MSC). For further understanding of these

CODECs, see: http://www.otolith.com/otolith/olt/lpc.html and http://www.speex.org/.

Robust DV is not “easy” to do on HF and may never meet everyone’s needs. A couple of

seconds delay is required for sync before voice can be decoded therefore fast break-ins

are not currently possible. And, DV is not as robust as SSB.

Setup

Text Message

Edit TX Text Message (voice mode only)

Selecting “Edit TX Text Message” will open up a window to enter text.

Up to 128 ASCII characters (including spacing) may be transmitted. Greater than 128

will be truncated in the receive window. Text messages can not be sent with data

(file/picture transmissions). Text messages may be sent, changed or deleted during a

voice transmission. The data rate is only 80bps, but the message is continuously

transmitted during the voice transmission. This may be used to send your QTH and

station info and will remain open after the DV transmission has been completed.

Allow RX Text Message (default)

Default provides a window for receiving the transmitted messages. This text message

window remains open for further review after the transmission has ended. (For more info,

see previous “Edit TX Text Message” description)

Setup

Save Received Files

Checked (default) indicates files received without errors will be saved in the sub-folder of

WinDRM named “Pictures”. If a file is missing segments, it will be saved in the

“Corrupted” subfolder. Both of these folders are initially created by WinDRM.exe.

Show Received Files

Checked (default) indicates error-free files will automatically be displayed (when

associated with a viewer such as Irfanview). Irfanview is the “viewer of choice” and may

be downloaded free at www.irfanview.com Irfanview requires a plug-in and must be

associated with the image file extensions (.jpg, jp2 etc) to display pictures. In Irfanview,

go to Options>Set File Associations>Extensions then select “Images Only” or just check

the extensions you wish Irfanview to display. Note: Received files and pictures will be

saved in the Pictures or Corrupt folders even if no viewer has been configured. Note:

Plug file name is typically named irfanview_plugins_xxx.exe (xxx = version).

Show Only First Instance

Checked (default) indicates only a single instance of an error-free file will be displayed

when received multiple times.

Soundcard

Opening the mixer will display the sound card’s “Recording” and “Playback” sliders for

Audio in and out. These are associated as follows:

RX Input = Mixer Recording Line-In (connect to receiver’s speaker)

TX Output = Mixer Playback Master Volume (connect to transmitter’s microphone input)

Voice input = Mixer Recording Mic-In (connect PC microphone to soundcard)

Voice output = Mixer Playback Master Volume (connect to amplified PC speakers)

For Digital Voice using a single sound card, inputs are switched under program control

(receive line-in switched to mic-in for transmit). Adjust mixer sliders for proper input

and output levels. Start with the “sliders” approximately one-third up. Only the

RECORDING microphone should be enabled. For transmit, PLAYBACK Master

Volume and Wave Out must be selected. Use the Master Volume for the coarse

adjustment and Wave out as the fine adjustment. Note: Uncheck/deselect all other

inputs/outputs. For decoded Digital Voice, Mixer Playback Master Volume must be

manually switched between the PC’s amplified speakers for receive and the transmitter’s

mic input for transmit. If two sound cards are available, set up one card for Receive and

the other for Transmit. Then, no manual switching will be required. Note: For ease of

setup/use, two sound cards are highly recommended Digital Voice. It is very easy to add

a second sound card especially if it is a USB. A low cost “USB 2.0 to Audio Adapter

w/Microphone Jack” card for (under $10) may be found at www.geeks.com. This is a

thumbnail size card (p/n HE-280B) and requires no additional drivers for XP. Just plug

it in, XP finds and installs the drivers and WinDRM will display both cards under

“Soundcard”. USB headsets may also be used (i.e. Logitech 250/350) For further help

with the Soundcard Mixer, see http://www.sagebrush.com/mixtech.htm

DRM TX Settings

Mode A/B/E (A = Ground wave B = Single to multi hops E = NVIS Multi-hops)

MSC Protection (Normal = 0 Slower Low = 1 Faster)

BandWidth (2.3Khz – 2.5Khz)

Interleave (Short 400ms – fast QSB Long 2sec – Slow QSB)

MSC Coding (4/16/64 Quadrature Amplitude Modulation)

DC Offset (50-350-5000Hz)

Clicking the Default button will result in the following DRM TX settings:

Mode MSC Protection Bandwidth Interleave MSC Coding DC offset

B Normal 2.5 Short 16QAM 350

Robust lowers the transmission BPS by changing 16QAM to 4QAM. Speed raises the

transmission BPS by changing Mode to A, MSC protection to Low and Interleave to

Long 2 seconds. Long interleave requires additional sync time. Voice requires 2.5kHz

bandwidth for the 2400 bps CODECs. 64QAM on a HF channel requires a higher SNR

and minimum multi-path to perform well. MSC Protection A, B and E provides different

levels of forward error protection (FEC) to protect the MSC from the detrimental effects

of QSB/QRM/QRN. B is higher than A with E (known as D in DRM) for Near Vertical

Incidence Skywave (NVIS) transmission where the signal is transmitted with a very high

angle of radiation short path propagation. In practice, however the extra protection for

this mode appears to have limited results. In DRM, Mode A is used for ground wave

propagation where Mode B for single hop/multiple hop propagation. The default mode

“B” on HF has shown to have the best overall performance. Mode E has been shown to

be the most robust in the presence of multipath and weaker signal levels.

Note: A BSR request may be made using different (larger to smaller QAM constellation)

DRM TX settings. This is sometimes done under poor band conditions in attempt to get

the request through lower SNRs. However, the originating station responding to this

request must send the response to this request (“Send bad segment report”) in the same

DRM TX settings it was originally sent.

DRM RX Settings

Default settings are:

Freq. Acq. Sens. Search Window Size Auto Reset

60 350 Enabled

Higher settings increase sensitivity for weak signals but with higher probability of false

sync. Fast Auto Reset has shown to be effective in providing faster sync recover under

poor signal conditions. These settings work well in the default mode, however this is a

good area for hams to experiment and find what settings are best under varying

signal/band conditions.

BSR (Bad Segment Report – automated)

BSR provides a procedure to repair (sometimes called a “fix”) a defective file or picture.

Normally, a defective file or picture is caused when the received station does not receive

all the memory segments error free (segment failed CRC check). Depending upon how

many segments were not received, the picture may not be displayed using the SPA (Show

Picture Anyway) or will appear unclear/blurry. When this happens, clicking on the

“BSR” button will open a window and show the number of segments “missing”. The

received station may then send a BSR “Request” to the sending station and request these

missing segments be resent so the file (picture) may be repaired and displayed. This is the

manual method and requires user intervention. The “automated” BSR completely

automates this procedure for P2P (point to point) transfer of files. Auto Open BSR

request, TX ARQ and RX ARQ must be checked to initiate this procedure. Note:

WinDRM does not look for activity on the frequency. The procedure simply relies on

timing between the tx to rx and rx to tx change-overs and does not “listen” on the channel

for other activity. Therefore, users should maintain control of the station while this

automated BSR is being executed, i.e. “attended” operation. Upon a successful Auto

ARQ exchange, the sending station will send “Good Copy” to the receive station’s

waterfall. Note: Up to 30 additional segments are sent in with the receiver’s BSR. These

“additional” segments are sent to ensure the receiving station is in sync. Up to four

multiple BSRs windows may be open at one time. There requests may be transmitted one

at a time or all can be transmitted by clicking on the “BSR send” button while any one of

these request are being made (during transmission).

Load last RX file

When selected, the last error free file received will be loaded in the “Select Files”

window. This is normally used when the entire file is to be re-sent.

Auto open BSR request

Automatically opens up the BSR window when a defective file is received. This must be

checked to initiate the automated BSR procedure.

TX ARQ

Automates the “send” request for the BSR

RX ARQ

Automates the “receive” request for BSR Note: For auto BSR, both transmit and receive

stations must have Auto open BSR Request, TX ARQ and RX ARQ checked.

BSR (button)

Bad Segment Report

When a picture is received with segments missing, a left click on this button will display

the number of segments. Press “OK” to request these segments be re-sent.

SPA (button)

Show Picture Anyway

Left click on this button will attempt to associate and display the last received picture

even if it the file is incomplete. If there is enough data for the picture to partially

assemble the picture, it will be displayed. Dependent up on the amount of missing data

(memory segments) and preference of the received station, the user may then click on the

BSR button to show the number of segments missing. Now, the BSR the request can be

made to resend the missing data. The picture above is an example of a picture displayed

using the SPA with missing segments.

Picture shown “repaired” after receiving the missing 35 segments using the BSR request

procedure. Note: This entire procedure may be automated when the “Auto Open BSR,”

“TX ARQ” and “RX ARQ” checked.

Example of the transmitting station’s responding to a BSR request. Note: This is not the

data used in the previous repaired picture.

G (button – works with Windows XP only)

Good (good picture received)

Left click on G will transmit a pre-recorded wave file displaying “GOOD” in

the received station’s waterfall. Filename: g.wav

B (button – works with Windows XP only)

BAD (bad picture received)

Left click on B will transmit a pre-recorded wave file displaying “BAD” in

the received station’s waterfall. Filename: b.wav

ID (button – works with Windows XP only) Left click on ID will transmit a pre-recorded

wave file displaying the transmitting station’s call sign in the received station’s waterfall.

Filename: id.wav

For help in creating these wave files, go to KB4YZ’s web site:

http://www.kiva.net/~djones/index.htm

TUNE (button)

Left click on TUNE will transmit a pre-recorded wave file for setting the proper output

level of the transmitter. Three reference pilot (sync) carriers will be displayed in the

received station’s waterfall. From left to right, A=1850Hz, B=1475Hz and C=725Hz.

With a properly adjust transmitter (good linearity – not overdriven!), the receiving station

will only see these 3 carriers. Any others displayed (at the receiving station) are products

of inter-modulation distortion which will degrade performance. See KB4YZ’s WinDRM

tuning file at http://www.tima.com/~djones/drmtune.htm. Non-linearity can cause

spectral re-growth of unwanted carriers. Driving the typical transceiver and/or power

amplifier too hard will cause this spectral regrowth (unwanted carriers). Yes it is just as

bad as it sounds and it should be avoided. Drive 100w transceivers to only 20w max

average and a typical 1kw amps to 200w average power. For the adverse effects caused

by non linear transmissions, see http://www.tima.com/~djones/DRM_power.htm

TX Pic (button)

Left click opens a window to add or remove files for transmission. Radio buttons enable

from 1 to 3 instances of the file be transmitted. Additional instances of the same file may

be sent by adding the file multiple times in the Select Files window. Long Leadin

increases the time for sync data at the beginning of the transmission. This is used in the

presence of weaker signal conditions or QRM to help ensure the sync is made at the

receiving station prior to sending the file data. Return button closes and returns to the

opening WinDRM display. TX button starts transmission of sync data followed by the

file data.

TX Voice (button)

Left click starts a voice transmission (or if in focus, tap the spacebar). The microphone

must be connected to the soundcard’s “MIC” input. The display graphically shows the

transmit microphone level (sound card’s microphone input). Adjust the mixer’s Record

slider while speaking across the PC microphone. Best results will be found when the

microphone input level is kept rather low while speaking in a loud tone of voice. Keep

the average level so peaks fill approximately 50-75% of the display. Speaking too loud

will cause the display to turn red. Some PC electret microphones have poor non-linear

response and may sound “basey” yet tend to accentuate the highs which cause high peaks

and distortion in this application. Experiment in this area to find the best microphone and

level for the highest speech quality The audio filter may help the intelligence of the

speech in some conditions. SPEEX sounds like it adds more fidelity to the speech (when

compared to LPC) but at the same time, it is a bit muffled and tends to “flat top” the input

easier. This is an area where a well chosen microphone (such as a one from Heil Sound)

will improve the voice quality. The input impedance of most sound cards microphone is

approximately 2500 ohms. This impedance may vary but should be a consideration when

choosing a microphone. The TX button name changes to “RX” while transmitting.

“Echo” of the decoded voice may be caused by some combinations of PC and soundcard.

This may be a soundcard latency problem related to the timing and transfer of data or a

ground loop. Changing sound cards may correct this problem. Known “good” low cost

sound cards include M-Audio, and Sound Blaster Audigy series. When retuning to

Receive, the button label will momentarily display “Wait” (for approximately 2 seconds)

while the transmit buffer empties. If the “Remote” feature is activated (PTT on DSR or

PTT CTS checked under Setup>PTT Port), the TX Voice button is disabled and will

display Remote.

Note: A very small low cost (less than $10 USD) USB sound card by C-Media (HE-

280B has shown to perform very well with WinDRM. It may be found at

www.geeks.com Or use a USB headset such as the Logitec model 250 or 350.

RESET (button)

Reset re-starts the sync process in receive. Normally, this button is rarely needed.

About

Info

About

Help

Typical connections between PC, interface and radio

See “Setup PTT Port” info in this doc for more information on these connections. Any

available com port 1 thru 8 may be used for all functions (PTT, Spacebar PTT, Remote

PTT and Transceiver Speaker Mute).

Further DRM technical info and software may be found at:

http://www.drmrx.org/, (DREAM 1.10.6cvs or later) and www.drmradio.co.uk

------------------------------------------ -------------- ------------------------------------------

updated 23-Jul-2008

Suggested Frequencies: (Warning – most of these are from web pages dated two or more years ago…things look bad)

80 Meters:

3.606 net, 7pm CST, usually daily except Saturdays

40 Meters:

7.130 2230Z net
7.096 EU
7.169.33, 7.170, 7.173, 7.177, 7.286, 7.291 (USB)
20 Meters:

14.255 EU

Monday-Friday daily net at 11AM Eastern time - 14.236
Saturday/Sunday net at 1900 UTC - 14.236

14.236 is most popular AOR frequency

17 Meters:

18.1625
15 Meters:

21.370

Sorry, many dead links on the AOR and FDMDV pages – especially the on-line finder for skeds

http://n1su.com/aor-ard-9800.html

http://n1su.com/fdmdv/download.html