This took quite a bit of drive compared to the amateur radio I had been using with the same TNC for testing, but the Kantronics KPC-9612+ has plenty of oomph to accomplish the task. With everything buttoned up, I adjusted the TNC for the appropriate amount of drive to get about 3kHz of deviation.
I soldered to the top of each pin here to gain access. To the left of CN2 (above, in the picture) is the external alarm socket, which contains labeled pins for E (ground) and SB (switched battery). The nice thing about the older TK-805 is that all the components are larger and easier to solder to. It takes a steady hand and a good eye, as these pins are tiny. Since the pins aren’t exposed on the bottom side of the board, I carefully soldered to the top of each as they leave the board and enter the socket. DEO is pin 1, DI is pin 4, and PTT is pin 7. The pins on the large connector are numbered from right to left, with the right-most pin being #1 and the left-most being #8. On the main TX/RX board of the radio, on the left side (if facing the front panel), there is a small group of three connectors, two small and one large eight pin socket labeled CN2. If you want to power your TNC from the radio, you also need SB (switched battery). In the manual, these signals are listed as DI (external modulator input), DEO (detector output), E (earth) and PTT respectively. In order to make high-speed packet work, you need access to the modulator for TX audio, the detector output for RX audio, ground, and of course PTT to transmit.
The service manual can be found on repeater-builder, which shows the various boards and the signals on each of the inter-board connectors. However, you can follow those instructions to remove the speaker jack, jumper the proper traces to enable the internal speaker, and route a cable through the resulting hole in the case for interfacing. This one is pretty common, but it actually only describes high-level audio connections, which aren’t suitable for high-speed stuff. This rig is similar to (but much newer than) the oft-used Kenwood TK-805, for which there are documents available about general interfacing. While you could use the well-documented mic and speaker jacks for 1200 baud, 9600 baud and faster require low-level access to the radio’s internals.
However, not much is available “out there” on how to interface it to a high-speed TNC. While not frequency-agile or field-programmable, it is more than adequate for a fixed installation, such as a remote base or digital mode transceiver. It is happy in the ham bands, has a good screen, excellent rubber-covered buttons, and is quite small and rugged.
There is a wide selection of mobile radio accessories available for the radio which is depicted below.The Kenwood TK-840 is a nice commercial UHF radio that is starting to go for $50-$100 on eBay due to the fact that it is not narrow-band capable.
Other features include, large 10 character backlit dot matrix LCD display, 3 digit sub display for system number, function / status LCD icons, renowned KENWOOD audio quality, companded audio, VOX, have 25W VHF, 45W VHF High Power, 25W UHF, 40W UHF High Power, 4W speaker audio, talk group ID lists, individual ID lists, caller ID display, 6 programmable backlit front keys, optional full DTMF microphone, call queuing, late entry, 2 priority monitor IDs, flash firmware upgrades, DTMF encode and decode, 12.5KHz & 25KHz channels, optional voice guide & storage, status memory, paging call, emergency call, emergency man down option, call key, time out timer (TOT), ignition sense, busy channel lockout, cloning, front panel test & tune, status messaging, short & long data messages, conventional & LTR zones, FleetSync & FleetSync II, PTT ID Digital ANI, power on-off messages, serial interface, QT, DQT, 2 tone decode, single & 2 tone encode, operator selectable tone, dual priority scan, list scan. The radio is capable of the following modes of operation: analog simplex, analog conventional repeater, analog LTR trunking. This radio has a wealth of robust features including VHF 150-174MHz & UHF 450-480MHz or 480-512MHz, 250 conventional channels, 600 trunked channels, 32 zones, 250 groups per system LTR mode.
The TK-780(H) & TK-880(H) series mobile radio is Kenwood’s high tier analog trunking radio which has all the features you need in an analog radio.
This is Kenwood’s newer and most robust full featured line of analog only radios and they will out perform the competition for any comparable price. The Kenwood series of TK-780 & TK-880 mobile radio products has many features to provide you with the ability to excel the performance of the radio system.