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The Amateur Amateur: Packet, Part 1

03/30/2009

Packet is like that. It's ubiquitous. It insinuates itself into your life and you never notice it. Think about this: This very column came to your computer via packets.

I suppose I first became aware of packet radio when my wife Nancy and I studied for the Technician exam. At that time it was just a bunch of more-or-less meaningless words: PACTOR, AMTOR -- just alphabet soup. But soon after getting our licenses, we got to see packet radio for real. We visited an Amateur Radio field demonstration being sponsored by the Suburban Radio Club (now the St Louis and Suburban Radio Club). It was a simple demo with just a few people, but one of the stations was running packet. I was kind of impressed. This was 1995, and at that time I hadn't see all that many computers operating in the field. And I had definitely never seen one connected to a ham radio.

After that I pretty much forgot about packet radio. I was having enough trouble with our home computer without trying to load strange software or add weird devices to it. Back then, it spent most of its time crashing and rebooting. It had apparently been placed on this Earth just to aggravate me, because that's all it did. It certainly didn't do anything useful.

Meet Me in St Louis

Then about four years ago some members of our ARESĀ® (Amateur Radio Emergency Service) group began to demonstrate digital modes at our meetings. They showed us PSK31, RTTY, SSTV and something called MEPN (the Missouri Emergency Packet Network). They illustrated how easy it was to run digital modes with our existing radios and computers. All of it could be done using our computers' soundcards. A lot of us got hooked on digital modes at that point, and nets using PSK31 and the MEPN have become a regular part of our group's activities.

I've heard a number of hams say, "Some of us played around with packet a while back. We don't do it anymore."

Let me tell you, a lot has changed. Oh, I don't mean to imply that there have been any Earth-shattering discoveries, such as little green alien packets from another dimension. No, the fundamentals of packet radio are pretty much unchanged. What has happened, though, is that various special interest groups have used packet radio as a foundation and have built some very interesting systems on top of it.

MEPN is a good example. It is an ambitious project to link together emergency agencies all across Missouri via packet radio. It has been designed so that the simplest ham radio and computer configurations can use it with little or no additional software.

There are even more far-reaching packet-based programs, such as Winlink and APRS (Automatic Packet Reporting System). And there are even higher-level systems built on top of APRS itself.

For my part, after I'd played around with RTTY, PSK31 and SSTV for a while I decided I'd also give MEPN a shot. After all, its ultimate purpose was emergency communications. And I was an emergency communicator, right?

But I am also The Amateur Amateur, so naturally, things didn't go quite as I'd expected.

(Peter) Packet Radio

Let me say right away that there was nothing wrong with the Missouri Emergency Packet Network. All of my difficulties had to do with my computer-to-radio interface.

It used to be that you needed a TNC (Terminal Node Controller) to link your computer to your radio. But there weren't a lot of TNC manufacturers out there, and the TNCs that were on the market tended to be a tad on the expensive side. Then some brilliant folks figured out how to emulate a TNC using a computer soundcard. It was a lot cheaper and it worked just as well.

Sometimes.

As it happens, packet radio is a lot more finicky than RTTY or PSK31, and the input and output levels of your soundcard must be set with the same precision as a Swiss watch. It can be done, but it takes a lot of fiddling. It's a lot like trying to parallel park for the first time. And unfortunately, once you've got everything set, it is very easy to undo the settings. You don't even have to do it yourself. Some random program in your computer will mess it up for.

Anyway, the soundcard adjustment problem put a crimp in my efforts to access MEPN. I could never get the settings right. Still, I had no intention of giving up (hams are obstinate, just ask their spouses).

It seemed to me that I had two choices. The first was to buy special software to manage the soundcard. The second was to buy a TNC. The cheaper, easier solution was to buy the special software. So, of course I decided to get a TNC instead (remember what I said about hams being obstinate?).

Actually, I bought a transceiver that had a TNC already built into it. It was an Alinco DR135T, and with a data port right on the back of it, I could run packet without having to run exotic connections through the microphone and speaker ports. That was nice.

Having a genuine TNC made all the difference -- I was able to run in packet mode and access the MEPN with no trouble at all. And I would like to end the column on that upbeat note. I'll save all of the unexpected debacles that ensued for next time.

To be continued...

Editor's note: ARRL member Gary Hoffman, KB0H, lives in Florissant, Missouri. He's been a ham since 1995. Hoffman says his column's name -- "The Amateur Amateur" -- suggests the explorations of a rank amateur, not those of an experienced or knowledgeable ham. His wife, Nancy, is N0NJ. Hoffman has a ham-related Web page. Readers are invited to contact the author via e-mail.

Gary Hoffman, KB0H
Contributing Editor



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