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Updating the Kantronics KPC-3 TNC

The currently produced Kantronics KPC-3+ is kind of the "gold standard" of 1200 Baud TNCs (Terminal Node Controller.) Just about any article you read about Packet Radio, VHF Winlink 2000, or APRS mentions the KPC-3+ and gives examples of how to program one for your application.

Prior to the KPC-3+ a model designated the KPC-3 (no "+") was manufactured. My understanding is that it went out of production because some of the parts were no longer available.

The original KPC-3 is still readily available at hamfests, eBay, and various sell, swap, and trade sites. Often at prices much less than half of the current $200 or so retail price of a KPC-3+. The KPC-3 was sold for several years and has various versions of firmware. For many applications that does not matter. For some applications such as APRS Digipeating the firmware version is very important.

Kantronics no longer supports the KPC-3 and will not provide firmware updates. Updating the firmware involves swapping the EPROM in your TNC with one containing the latest firmware. That is Version 8.2 to the best of my knowledge.

Mike Freeman runs the website/Blog called Freeman's Garage. He has details on how to upgrade your old KPC-3, links to the V8.2 EPROM firmware that you'll need, and links to PDF manuals that describe the original KPC-3 and the new features/changes added by the V8.2 firmware.

Mike recommends buying an inexpensive EPROM programmer to program your own chips. If you don't imagine needing this capability for other projects you might ask around your local radio club. It's a good bet someone already has a suitable programer. It only takes about 30 seconds to program and verify an EPROM.

The original EPROM in the KPC-3 is a ceramic body 27C512 part. The "E" stands for erasable and the part has a small clear window that is covered with a small label. By shining ultraviolet light through the window for a few minutes you erase it so it can be reprogrammed. EPROMs are not often used in newer products. The ceramic bodied "window part" is expensive to produce and new parts can cost as much as $5 each.

I upgraded my KPC-3 using a One Time Programmable or "OTP" part. The down side is you cannot erase it because there is no window. The upside is the body of the part is plastic so it's less expensive. Since V8.2 was the last version released for the KPC-3 you're not going to be changing it again so there isn't a need for reprogramability.

The OTP part was $2.06 in March 2010. I bought mine from:

Mouser Electronics, Part #511-M27C512-90B6.

By the way, if you are ordering parts anyway, the coaxial connector used to power a KPC-3 or KPC-3+ is a 5.5mm O.D., with a 2.1mm hole for the center pin. (Kobicon 1710-0721.) It is also available from Mouser and it never hurts to have a spare or two:

Mouser Electronics, Part #1710-0721.

You can get these parts or comparable from a variety of suppliers. Mouser is one of my favorites because they do not have a surcharge for smaller orders and have never objected to orders with one or two pieces of an item.

NOTE: In July of 2011 I got a note from Chris NØTTW saying that the OTP part I mentioned above is no longer available. He found what appears to be an acceptable substitute -- an Atmel AT27C512R-70P. It should be available from Mouser and other electronic distributors.

73, Tim N9PUZ
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