Icom f521 VHF for packet

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emd001

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Hey Everyone,
As the title states I have an ICOM f521 and f621 that I no longer use and would like to repurpose them. I am thinking I want to use the f521 for packet radio, at this point APRS. I have no idea where to start. I know I need a TNC connection to a computer from the radio, can I use something like a signallink or is it just the programming cable going to a usb port? Any point in the right direction is much appreciated.
 

W9BU

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If you want to do AX.25 packet, and APRS uses AX.25, I would recommend against the Signalink products. The Signalink USB has a built-in sound card, which is useful for sound card based data modes, but it keys the radio using was is basically a VOX circuit. In other words, it keys the radio when it detects audio on the transmit line. A real TNC keys the radio when the AX.25 logic in the TNC says it's time to key the radio. It's a slightly different approach, but the TNC is just more reliable.

Your TNC options among currently available products are:

The Argent Data and Byonics products are specifically made for APRS, but they can function as standard TNCs. If you are going to get into standard packet, the KPC3+ or Tiny-2 might be useful because they have a built-in mailbox for packet messaging.

You can find lots of earlier KPC3s on the used market, but you'll need the version 8.2 or later firmware to get standalone APRS features. You may also find some MFJ 1270Bs or AEA PK-88s on the used market that will work just fine for regular packet.

The advantage to a TNC that can do standalone APRS is that, once the TNC is configured, you don't need a computer. One of the highest-profile APRS digipeaters in Indianapolis is running a KPC3+ standalone. I run a fill-in digi just west of Indianapolis with just an Argent Data Tracker2. Neither site has a computer attached to the TNC. Of course, for a human to interact with the APRS world, you'll probably need a computer. Or, to run an APRS I-gate, you'll need a computer.

With any of these products, you are going to have to figure out how to access the receive audio (preferably detector audio), the transmit audio, and the PTT in the radio. Many of the Icom commercial radios have provisions for an optional accessory pig-tail that brings out those signals to a DB-9 connector. There's some information on the Repeater Builder site about accessing these signals in earlier Icoms which might apply to your radios. My aforementioned digipeater runs an Icom IC-F1020 with the OPC-617 accessory cable.
 
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