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

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

By Boone Barker, KC7RK October 3, 2009

I was a student in the ham radio class taught by Curt Black WR5J during the summer of 2009. Included in the class were Lee N7KC, Bob K9PQ, Tammy WA7TZ, Glen K7GLE and others. We learned about and experimented with a variety of digital communication modes, many of which could be useful for emergency communications. I know that everyone who participated enjoyed the challenge of learning about digital communications. We all owe Curt a huge debt of gratitude for his success in making this a fun experience.

This paper is my effort to recap the summer sessions and some key points that I wanted to remember. Full descriptions and more are in the WA-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 Net hosted by Curt Black, WR5J.

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

Curt emphasized that nearly everything came from the internet somewhere and sources were cited each time. Only of little of the information was based on direct communication with the authors of the software—only when he had questions on how to make something work or what was the current best approach for achieving some objective.

Training purpose: explore and experiment with a variety of digital 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 Blog Post script for each session. The information below is only a very brief summary of each session; go to the corresponding Blog Post for complete directions and information.

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

Participants were asked to have a computer, VHF and HF radios and—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 Digital Communication, Software and Modes

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

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

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

Session 5 WSPR – Weak Signal Propagation Reporter

Session 6 MMSSTV Slow Scan Image Transmission

Session 7 Digital SSTV EasyPAL

Session 8 WSJT-JT65A – Terrestrial HF

Session 9 WSJT-HS-Meteor Scatter

Session 10 Packet Radio Using Flex32

Session 11 Packet Radio Using AGW Packet Engine

Session 12 WINDRM – Digital Voice

Soundcard to radio interface options

• Acoustic coupling: 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
• Hardware: range from very simple ones for a few bucks to $100 for a Tigertronics SignaLink USB. If you want to keep going you can go up to a $369 US Interface Navigator - Lots of choices.

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

Software now available

• Multifunctional: Multipsk, MixW, Ham Radio Deluxe and 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 the next session.

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

The group owes much of what we know about FLDIGI and the Narrow Band 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, FSK Hell, 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 and with from 8 to 32 tones
• PSK: BPSK-31, QPSK-31, BPSK- 63, QPSK-63, BPSK- 125, QPSK 125, 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 remote signal that is transmitting a steady carrier.
• Tune: generates a continuous single frequency audio signal at 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 detailed instructions. A summary: Go to the web site at http://www.pa-sitrep.com/NBEMS . Follow steps on the left side of the page to get the FLDIGI software, install, and configure it. Calibrate your sound card offsets by downloading and running CheckSR from 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 OS users 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.html and go to it for info on various modes, and for an index of sights and sounds 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 the current state of your audio mixer in a settings file, and to restore the mixer to that state whenever you want.

Try out FLDIGI using some of the following modes and frequencies.

PSK – narrow band low symbol rate modes using single carrier differential Binary Phase Shift Keying, BPSK, or Quadrature Phase Shift Keying, QPSK. This is the most popular digital mode by far. Common PSK31 frequencies: Daytime: 14.070 MHz/USB, 10.140 MHz/USB, 7.070 MHz/USB Evenings/Night: 3.580 MHz/USB, 7.070 MHz/USB, 10.140 MHz/USB

MT63 employs a unique highly redundant Forward Error Correction system which contributes to it robustness in the face of interference 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 low error rates, but can be annoyingly slow.

• HF USB ops – (500Hz/16 Tones): NBEMS recommended USB frequencies: 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 used without Forward Error Correction, as it is very robust. The default speed (11 baud) was designed for NVIS conditions (80m at night), and other speeds suit weak signal LF, and high speed HF use. The use of incremental keying gives the mode complete immunity to transmitter-receiver frequency offset, drift and excellent rejection of propagation induced Doppler.

• Default calling mode - DominoEX11. NBEMS recommended USB frequencies: 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 Good Signal

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

Hints to new PSK users from that presentation:

1. Make sure you are putting out a pure signal. Don't overdrive the rig.
2. Ask on the bands for a report from others – the software of the person receiving your signal can report your IMD – should be less than minus 24dB.
3. Don't type in all caps.
4. Lower your power to a level of 50% of what your rig can produce so you don’t burn out your finals.
5. Tune a little above the PSK activity and call with Hell or MFSK16 or Olivia 16/500.

All PSK31 frequencies

160 meters 1.838 MHz

80 meters 3.580 MHz

40 meters 7.035 MHz

30 meters 10.140 MHz

20 meters 14.070 MHz

17 meters 18.100 MHz

15 meters 21.080 MHz

10 meters 28.120 MHz

6 meters 50.290 MHz

2 meters 144.144 MHz

1.25 meters 222.07 MHz

70 centimeters 432.2 MHz

33 centimeters 909 MHz

Note: you will frequently see the wider signals of PSK63 just a 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 by right clicking on the button. Other sets can be accessed by clicking on the end of the bar. Left or right clicking on the mode button brings up options.

Waterfall: the size can be adjusted and magnified.

2-minutes buffer: constantly saving the audio so that a new signal in a different mode can be selected for decoding of that last 2 minutes.

Signal to noise and intermodulation distortion 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 file to either single or multiple stations and allow each receiving station to verify that the transmission was received without error. Blog Post 4 has detailed 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 one of the RX/TX modes handled by FLDIGI if the sending station is using the feature. In receive mode it can be activated by clicking on the RSID button in upper right.

RTTY (Radio Teletype) is the second most common digital mode.

Look to the following websites for RTTY guidance:

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

RTTY frequencies:

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

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

30 meters: 10110 to top of band

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

15 meters: 21080 - 21100

10 meters: 28080 – 28100

Note: RTTY allocations for 40 meters vary greatly all over the 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. The ARRL promotes 7040 as the RTTY DX calling frequency, but the CW QRP’ers use it as 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 offers the most sensitive modems and detection routines available and many modes (such as ALE-400) that are not available in any other software. The challenge is his user interface is very dense and can be tough on a first-time user. His philosophy is he wants all the controls in one place – and they are.

FLDIGI is a very elegant package that is fully featured but simple to setup and use. HRD is not so simple, but is a great package and when used with DM780 is very fully featured. MULTIPSK offers the most sensitive modems and detection routines available and many modes (such as ALE-400) that are not available in any other software. The challenge is his user interface is very 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 and a 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 $50 required after a 15-day trial period. http://www.mixw.net/index.php?j=downloads

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

Session 5 WSPR – Weak Signal Propagation Reporter

Joe Taylor, K1JT, of Princeton has written a series of programs for brilliantly combining Digital Signal Processing (DSP) and ham radio to allow 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 to test propagation paths on the MF and HF bands. Users with internet access can watch 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 from the “Audio Device” list on the black WSPR screen that comes up at startup. Note that 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.htm to keep your computer clock accurate to within 0.01 sec.

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

Try operating at local sunrise or sunset to really see what 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 the program, or instructions in the WA-DIGITAL Yahoo Group files.

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

Suggested SSTV frequencies:

· 10 Meters: 28.673 28.677 28.680=calling frequency 28.683 28.686 28.690=K3ASI repeater 28.700=ON4VRB repeater

· 15 Meters: 21.334 21.337 21.340=calling frequency 21.343 21.346 Avoid SSTV around 21.350 because there is a Phone DX Net running

· 20 Meters: 14.230=calling frequency 14.233 14.236 14.239 Avoid SSTV on 14.227 because there is a Phone DX Net running there.

Application Notes

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

To use this software, just go to the SSTV watering holes at 14.230 or 14.233. This is the best known and possibly the best defended frequency in all of amateur radio.

The Ten Commandments of Slowscan by Dave Jones - KB4YZ

1. Use voice before sending SSTV.
2. Wait for voice and SSTV traffic to finish before sending SSTV.
3. Choose an SSTV mode that is proper for the image to be sent, band conditions, and the receive capability of the receiving stations.
4. Announce the SSTV mode used prior to sending.
5. Transmit on frequency as confirmed by calibration of the VFO with WWV.
6. Send straight pictures as confirmed by calibration of the clock timing with WWV.
7. Send quality pictures with call sign on image.
8. Send full frame.
9. Avoid sending a CW ID unless required by regulations.
10. Describe the picture only after it is confirmed that it was properly received.

Session 7 Digital SSTV: EasyPAL

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

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

SSTV frequencies are listed above.

Application notes

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

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

[N.B. EasyPal could be a powerful tool for emcomm. It could be used to 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. It facilitates basic digital communication using protocols explicitly optimized for a 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 are identical except for the spacing between transmitted tone intervals. At the present time JT65A is generally used on HF and 50 MHz, JT65B on 144 and 432 MHz, and JT65C on 1296 MHz. JT65 uses 60 second transmission and reception intervals.

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 can be found is to use your web browser and go to the JT65 Terrestrial Link web site by N0UK at http://www.chris.org/cgi‑bin/jt65talk .

The most commonly used JT65A frequencies are: 14.075 to 14.076 7.075 7.076 in North America 7.042 to 7.043 7.025 LSB for Europe and Oceania 3.576 (North America) 3.796 (Europe) 18.102 & 18.106 10.147 21.076 24.910 1.805 to 1.808.

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

Application Notes

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

As before, input volume level is critical.

Soundcard oscillator calibration is also important. See the help files.

Operating with WSJT

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

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

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

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

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

5. If you have received RRR — that is, a definite acknowledgment 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 that reminds you of the recommended procedures.

Digital on Six at http://www.ykc.com/wa5ufh/DOS/index.html promotes the use of digital modes on the 6 meter band. A weekly event is the JT65B activity on Friday evenings in 2 phases: 9:00 pm Eastern and then 8:00 pm Pacific time. Default Mode JT65B on 50.294MHz. When the "Band Is Open" QSY to PSK / Olivia / etc. on that mode’s appropriate calling frequency. 50.260 WSJT Modes (Calling Frequency) 50.290 PSK31 50.2925 Olivia 50.294 JT65B & Friday Activity Period Calling Frequency 50.300 RTTY and MFSK

Session 9 WSJT-High Speed-Meteor Scatter

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

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

Go to Ping Jockey Central at http://www.pingjockey.net/cgi-bin/pingtalk and 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 WSTJ Yahoo 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 always be made at least 5 kHz away from the calling (CQ) frequencies.

"CQU5" means "I'm listening and will reply Up 5 kHz." "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 HSMS operation 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 same direction 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 Ham with a VHF transceiver and a soundcard-equipped computer, at little or no expense.

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#new for a tutorial by Charles Brabham N5PVL with download and installation instructions. Two programs are downloaded: flexnet32.zip this file contains the Flex32 software, some assorted drivers, and a simple terminal program and soundmodem-flex.zip this is the soundcard driver module, along with a setup utility.

Installation: See Blog Post 10 for details. Briefly: Unzip into C:\FLEX32. Run soundmodem.config to configure soundcard driver. Run Flexctl.exe to bring up the Flexnet Control Center and add “soundmodem” to the channel parameters. Create a command-line shortcut to Tnc32.exe with parameters “call‑sign 4 4” to bring up TNC32. Key Esc to enter command mode and key H to list available commands. This is a simple terminal program that 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.html for 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 help file is still in German.

Paxon download is at http://www.paxon.de/download.html for 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 the connectable 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 first connect with Paxon. Have Fun!

Try browsing around in Paxon's "Settings" and you will be amazed at all of the nice things this program can do. It can be used for file 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 all the traffic between packet applications and the computer/radio interface—TNC or soundcard. 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 and configuration 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 free and then $59 license fee. The SV2AGW web site also has software downloads for AGWTerminal and AGWMonitor, both useful accompaniments to AGWPE.

Application Notes

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

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

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

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

The problem with digital voice modes is the loss of the use of a proprietary codec. Digital voice is about dead and probably will remain that way until a MELP equivalent codec is found or some new technology is found. See Blog 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 the group web site at http://groups.yahoo.com/group/wa‑digital/ has a large collection of files and information about digital communications for Radio Amateurs. If you are interested in this topic but not yet a member of the group, please consider joining.

October 5, 2009