Sunday, April 10, 2011

Getting started with HF Packet Radio

Shack glowI'm enjoying some time off between jobs at the moment. When I get up in the morning, it's as if a mystical glow draws me to the shack.

My electronics and radio room is very small - I have to slide in sideways to fit in the door. It's tucked behind the television in the lounge room.

The first projects have been to route antenna coaxes from other parts of the house in through the ceiling of the shack. I now have 80m, a half sized G5RV and 2m all going in there.

The next project was to get a PacComm TNC-320, which I purchased at the last "Trash and Treasure", working. It's been a bit of a struggle, so I thought I'd record these notes for others.

There's a lot of material out there about packet radio, but it's often very detailed and fails to answer the "obvious" first questions.

One problem for me is that while the TNC (Terminal Node Controller or modem) came with a quick reference card, the manual is lost and PacComm don't seem to put them on their web site.

I found the wiring required for a cable to my Icom radio's accessory socket here.

Tnc 320To get started I'm using a serial USB adapter (with a gender switcher) and the unix minicom serial terminal software.

There is frequent activity on 40m but I couldn't decode it. Patrick, VK2PN gave me some clues about the baud rate I should expect (300 baud) but still no luck. Finally doing a RESET on the TNC seemed to fix whatever brain scrambling it had suffered and it started decoding.

Now I'm seeing traffic with the dial set to 7037.17 LSB at 300 baud. Stations I've seen so far include VK2RX, VK4ALN-2, VK2WL, and VK2TT.

Up at 7039.15 I can see VK2AAB and VK2SLM who seem to be transferring a jpeg image with lots of re-tries - not too interesting to watch!


I have successfully connected to another station, so I know it works. Unfortunately there was no-one there and so I stumbled around for a while trying to figure out how to break out of the connection. (I even tried +++ like the old days with Hayes modems {the trick is Control-C}).

TNCs have a huge command set. Here are the ones I've used so far:

  • reset - to return to factory settings
  • mycall VK2TPM - to set your call sign (replace VK2TPM with yours!)
  • monitor on - display traffic (it was on by default)
  • connect VK2XXX - to connect to another station, (to get back to the command prompt use ^C)
  • disconnect
  • display - show all settings
  • mheard - display a list of all stations heard by the TNC
  • mhclear - clear the list of heard stations

I failed to find any friendly packet software for Linux so I've switched back to Windows and am currently using WinPack v6.8. It adds a little to the terminal interface but I'm hunting for something better.

The TNC-320 looks to have some interesting built-in capabilities including a mailbox store, more investigation is required.

Having used PSK31 on 20m for digital keyboard to keyboard chat, which works really well and is easier to tune thanks to the waterfall display, I'm not sure that we still need TNCs but I'll have a play around and see how it goes on 40m.


Anonymous said...

It is not the 320, but I would be the command set is similar if not the same:

Should get you a bit of the way. As for the no packet software in Linux. You should put the TNC in KISS mode (if it can do it) and just use the call program along with many other programs that can run with a TNC in kiss mode and run most anything you want.

If the TNC becomes old, you can always use your sound card and a simple circuit to key up and have fun without the tnc. Soundmodem link:
How to set up soundmodem:

Have fun and hope to see you on HF some time. KB0GBJ - limited to 10M due to the fact I have not yet gotten off my duff and taken my general test yet :-)

Peter Marks said...

Thanks KB0GBJ,

I hadn't thought about kiss mode but I'll definitely try it out.