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[W4XKE]

I am putting an APRS station together and just received my new Kantronics KPC 3+ TNC unit.  I bought the modem cable today to connect it to my computer's serial port.  My next item on the agenda is to connect the Yaesu FT-50RD handi talkie to the TNC.  I would like to take a shortcut on this and use the cable that came with my ADMS software programming kit.  I have been cautioned on doing this as it may risk damage to the radio, the cable and the TNC.  I would like to ask if anyone else has ever done this successfully?  Questions in my mind concern the pin-outs of the ADMS cable... do they coincide with the TNC cable requirements?  Are there any hidden components in the plugs of the cable?  Is the cable shielded, so as not to cause RFI to the station?  Should I just try to buy a 4 conductor microphone/earphone plug and make up my own cable as per the KPC 3+ instructions?  Help me out here, guys.  I know someone has tried this before me, so talk to me.  Respectfully,  Johnny W4XKE

[KC0HBM]

The ADMS cable usually only makes one connection: to the data input of the radio.  My Yaesu VX5r also uses the 4 conductor plug.  The second "ring" from the tip is the data connector (from Yaesu's manual), and when I opened up my programming cable I verified only two wires are used by the circuitry to connect to the radio(DATA and GROUND).

APRS/TNC need access to audio and mic/PTT lines.  Basically your TNC "listens" to the audio from you radio and decodes data from what we hear as bursts of noise.  It can also "key" the radio and generate its own noise just like a human operator talking into a mic.  So you programming cable is going to be useless because it never connects to the audio/mic lines (these connections are the tip and third ring of the 4 conductor plug)

I dont know about damaging the TNC, but I doubt you will damage the radio if you did try.  the radio should ignore anything on its DATA connection unless its in clone mode.  Don't take my word for it, its best (and cheaper) to err on the side of caution!

Follow whatever instructions you may have received with the KPC or check out www.packetradio.com - they have alot of good interfacing information.

Mark
KC0HBM