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A Cheapskate's Approach to Packet Radio (Part 1 receiving)


Packet radio Terminal Node Controllers (TNCs) are packet radio modems capable of communicating with each other over the air using the AX.25 protocols running at 300, 1200 or 9600 baud.

The radio side has connections for transmit and receive audio as well as the PTT (press to talk). The TNC also has a 12 volt power input and an async serial data connection allowing it to communicate with a computer (and human).

When operating packet with VHF radios, most use 1200 baud because it works well with voice radios and is a relatively forgiving data mode.

Since packet radio is an old digital mode, it's hardware is often found at hamfest flea markets. Some common brands were Kantronics, MFJ, Pacomm and AEA.

Because the TNC's are often 30 years old, they sometimes need some TLC to use them again.

My point here is your mileage may vary.


Another option that can work well is a virtual software TNC running on your computer.

This method uses the computer's sound card to listen for and emit the 1200 baud modem audio (packet racket the old timers called it).

While there are likely options for every computer type, I'll discuss a popular Windows program suite.

A Ukrainian Ham named Andre UZ7HO has created and maintained a popular packet radio program who's latest version is called soundmodem114.

He also has a terminal program called easyterm49 that operates seamlessly with soundmodem running.

The terminal program provides the user a TNC like interface that is functional and uncluttered while soundmodem is like the packet "engine under the hood".

Installing:

Andre's packet radio TNC webpage:



The 3 files needed:

soundmodem114.zip

easyterm49.zip

user_guide114_EN.zip

I created a sub directory named /packet which holds the unzipped programs.
Unzip the downloaded files to your new directory.
Make desktop shortcuts for the programs.

The user_guide114_EN.zip is a very handy .pdf document.


Receiving packets:

The following assumes your computer soundcard's MIC input is connected to a 2 meter FM radio's audio out. This usually takes a 1/8" stereo connector patch or jumper cord.

Set the frequency to a packet channel like 145.670 (local node WILMAR) or 144.390 APRS. You'll want some activity to see things work.


First start the soundmodem114 program. Then start the easyterm49 program.

The unplugged volume should be adjusted low audible with squelch open. When the program is running and it's hearing the radio's open squelch, the effects should be visible on the waterfall display.

An outdoor antenna will likely yield much more packet activity than one indoors, which will likely only hear the local node WILMAR.

When a packet is decoded you will see it a a lot of info on the soundmodem screen, while the easyterm screen is much more like what you would see with a real TNC.

Once you get it working, one of the fun things to do is listen in on the International Space Station (ISS) when they pass overhead several times a day on 145.825 MHz.

You might even hear me use them as a APRS digipeater, sending the world my location.

73
Mike N0QBH

Hi Randy!

I'm looking for a user interface that adds TNC functionality to Direwolf.
Any suggestions?
I'm looking for low cost ways local users can explore packet radio.
Direwolf with a Signalink USB is attractive because the Signalink is so versatile for all sorts of digital ham stuff, one can justify the investment.

73
Mike N0QBH?

I am getting active in the VHF/UHF world again after a long hiatus away.
A bit of history...
Back in the 1990's when I was active, packet radio was all the rage and my forte.
We had a thriving packet THENET network here in the Willmar area with a 100' high wide area node (MNWIL) out at the college and another on the Spicer Dietz Bros tower at 150' (MNSPI).
A UHF 9k6 baud backbone was constructed from Minneapolis to a high natural site near Cold Spring. That node fed St Cloud, Little Falls to the north and Willmar to the south.
We had from 1 to 3 BBS services going at any time which were tied into the world network so you could "e-mail" other hams all over the world. We also seen our first "flame wars" there, a precursor to today.
Several local hams had a personal computer attached serially to a TNC (packet modem). The modem has transmit, receive audio, built in PTT and connects to a 2m transceiver or even handheld.
That was all you needed to get on the air. We had a blast!?

Fast forward to today - the Internet made packet radio seem obsolete and it evaporated.? Ironically, in the packet era, the Internet was the Holy Grail.

I discovered there was an active 2m 1k2 baud node operating in Willmar on 145.670 called WILMAR.
I had some issues using it until I figured out it would only do a full connect if I used the alias WILMAR. I was trying to use the callsign associated WB0MNU-15. That doesn't do anything but connect and wait for a password or something.
The rest of the MN network is at least 2 hops away during the day, and may be better at night. However, a local node allows the locals to either keyboard to keyboard qso or e-mail to other's personal mailboxes using modest antennas and power.
Since most hams today don't have TNC modems, I'm experimenting with a software packet package called Direwolf. So far, I've found it works great to receive, but haven't the additional program(s) for full TNC capability located - yet.
I am going to try make the Oct club meeting and meet the gang.
73
Mike Berg N0QBH

?

Noticed I could key the .91 with and without tone encoding today.?

Problems?
73
Mike N0QBH

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Ten Ten International Summer QSO Party

The Ten Ten (10-10) International QSO Party is this weekend, beginning at 0000 UTC on Saturday, August 5, and concluding at 2359 UTC on Sunday, August 6. The 10-10 QSO parties are a great way for anyone interested in operating on 10 meters to get on the air. All amateurs with operating privileges on the 10-meter band may participate. For rules and other information about Ten Ten International, visit?.