By Gary Hoffman, KB0H
Contributing Editor
May 1, 2010

I often hear people say, “Oh yes, I know how to program a computer”, when what they really mean is that they know how to invoke some esoteric feature of Excel or Word. As a software professional, I do not consider that sort of ability to be anything remotely like actually programming a computer.

But I have to admit that I lapsed into the same erroneous mindset. Not with computers, of course, but with packet radio. Having connected a transceiver to a computer, and having sent and received packets, I blithely believed that, oh yes, I understood packet radio. Recently, however, I learned that, oh no, I didn’t.

Engineer

I didn’t think that packet radio was plug-and-play, mind you. My first efforts did involve a fair amount of puzzled frowns and head scratching. But, other smarter souls had gone before me and had at least left some well-marked trails. I also followed the path of least resistance, in that I bought, rather than built. And what I bought was for a very specific application.

I understood well enough that I had not conquered the field of packet radio, at least initially. But over time, complacency crept in and I eventually did start thinking that way. Hey, my packet application worked, so I must know what I’m doing. Right?

Before I proceed with the rest of my tale let me briefly describe my stations. There are two of them, and most of the time they both reside in my shack.

The first and oldest consists of a Yaesu FT-847 and a Compaq desktop computer. The FT-847 can operate on the HF bands, as well as 2 meters and 70 cm. I call my Compaq “Longwave.” I refer to this computer/transceiver pair as my “base station.”

My second station consists of an Alinco DR-135T 2 meter transceiver and a Dell Inspiron 1150 laptop computer. The computer’s name is “Surprise.” (does anyone give names to their transceivers?). This pair is, as you’ve probably guessed, my “field station.” though most of the time it is solidly plugged into power, antennas and other ancillary items in my shack.

Although I had operated in various digital and data modes on my base station, virtually all of my packet work was done on my field station. The reason was simple: The Alinco came with a built-in TNC (Terminal Node Controller).

I don’t want to put down the Alinco, or any of its components. They did the job that I originally wanted them to do, which was simple terminal-to-terminal communication through a digipeater. But the day came when the Alinco’s built-in TNC (a Tasco modem) wasn’t quite up to performing a new task that I was attempting, namely running Winlink. I was able to find a work-around, more than one, actually. But the initial failure of the Tasco did start me thinking about better, more robust TNCs.

One of the work-arounds that I mentioned actually was to buy a new TNC. I got a Kantronics KPC3+, which seemed to be a very popular model. It was vastly superior to the Tasco modem in many ways (and much more costly), but I only used it on the Alinco once. Yes, it worked fine. But the KPC3+ was an external TNC and the Tasco was internal. Connecting the KPC3+ required running wires to the Alinco’s microphone and speaker ports, making it a dedicated packet transceiver. If I used the internal Tasco modem instead, I could jump back and forth between operating in packet mode and operating in voice mode.

I set aside the KPC3+ with the idea that I would one day connect it to my base station. For my field station though, I decided that I would stick with the internal Tasco modem. If I needed to run Winlink, there were a few more work-arounds that I could put into play.

The Knack

One day, I found out that there was a beefy replacement for the Tasco modem -- the Argent T2-135. Argent made a number of APRS products and the T2-135 was designed specifically to fit into an Alinco DR-135. Oh boy! I just had to have one! I begged my wife Nancy, N0NJ, to get me one for my birthday. And she did.

And that was the beginning of my harsh education on TNCs. I was about to learn that there was a lot more going on than I had ever imagined.

I had no difficulties installing my new Argent T2-135 TNC. The Alinco was easy to open. The Tasco modem came out without a fuss. The T2-135 slipped right in. I closed up the Alinco and reconnected all of the cables. I was a happy ham.

Until I cranked up my computer and called up the packet software I had been using. I couldn’t connect to the digipeater. In fact, it didn’t look like the Alinco was transmitting at all.

At that point I remembered that AGWPacketPro, the software that managed the TNC, had a setup page that asked which model was being used. I called up the page. Hmmmm. The Argent T2-135 didn’t seem to be listed. I tried some generic TNC settings, but none of them worked.

Okay, time for Plan B -- switch to simpler software until I got my bearings. I called up Microsoft’s Hyperterm. Gee, that didn’t work, either. I simply could not connect to the digipeater.

It was time for Plan C, which was to read the instruction manual. I had finally grasped that TNCs were not completely interchangeable. It was not going to be a simple matter of popping out an old TNC and popping in a new one.

Confusion

I read the instruction manual. Then I re-read it. Then I read it again. The very first thing that struck me was how complex the Argent TNC was. No, let me rephrase that: how rich it was. It could do a multitude of tasks that I had never imagined. My simple terminal-to-terminal application was just the tiniest fraction of a much larger packet radio world.

The second thing that became apparent was that the one command that I wanted -- the oh-so-vital “Connect” command -- did not seem to be in the T2-135’s menu. That was a little disturbing, but I’d already found that the terminology varied from manufacturer to manufacturer, so I wasn’t terribly worried. I just needed to find out which command to substitute for the “Connect” command.

I couldn’t find it. So I sent e-mail messages to our local digital gurus asking for help. Surely they would know. In the meantime, I started looking around Argent’s Web site to see if they had supplemental information. They did, in the form of a Yahoo discussion group. I went over to the Yahoo page, looked around and yes! Someone had encountered exactly the same problem that I had! They had posted the very question I wished to ask. And the answer was…

The T2-135 didn’t have a “Connect” command. There was no “connected” mode. The device was designed to run a myriad of APRS applications, but nothing like a simple terminal-to-terminal operation.

Despondent, I removed the T2-135 from the Alinco and re-installed the Tasco. I didn’t consider the affair to have been a waste of time, as I had learned a whole lot about TNCs and their capabilities. And I’m sure that sooner or later I will get into APRS and the Argent T2-135 will suddenly become my best friend.

A while later I did receive responses from the local digital sages. They confirmed that the T2-135 did not have a “Connect” command. They assured me, however, that there was a work-around.

Dazed, I could only shake my head. Hadn’t I just left this party?

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 at kb0h@arrl.net.