Cables and connectors for connection between the PK-232 TNC and Yaesu FT-847 for HF

There are a few issues to be aware of. In the case of using the Data port in the FT-847, there is a hang time on the PTT that is too long for Packet QSO's to be viable. I posted a message in the Packet Radio Forum that I belong to and another user of the FT-847 had the same issues and resorted to the Front Mic Connector, and rear Ext Speaker for the connection. That started to look a bit of a cable nightmare when dealing with all the other cables I have here. I had a bit of a google around and fell upon a note in a page about long changeover on the FT-847 and there was another way.

The note said that some people had good results with using a 100nF (0.1uF) capacitor or 200nF (0.2 uF), so I set about trimming off all the nice neat heatshrink that I'd put on when making the cable up. Replacement of the capacitor for a 100nF has speeded up the transfer to one that will now support AX-25 Packet.

Anyway, I learned so you don't have to. You can either build the cable as I have below or experiment with a different capacitor value. There are also notes elsewhere that say to up the resistor to a 2.7k Ohm one but there is little explanation of why.


FT-847 Data Connector for HF Digital Modes

The FT-847 uses a 3.5mm stereo jack for HF digital signals, and therefore is fairly easy to connect to a TNC. The difficulty with the PK-232 is the lack of TNC connectors, if you are not lucky to get cables with your TNC. I didn't with any of my TNC purchases, so looked around in the supplies boxes and USB 5-pin Motherboard headers work just fine. These are wired to a small piece of strip board to populate the Capacitor/Resistor circuit to provide PTT, as designated by the Yaesu Radio User Manual.

The cables need to be at least shielded and wired to provide good ground connections between the TNC and Radio, else ground loops will give poor signals, transmit and receive. I have used JY-8022 Audio Cable (Twin shielded cable, in 8-form), Neutrik 3.5mm Jack and a homebrew TNC connector.


JY-8022 Twin Audio Shielded Cable
2k Ohm 1/4 watt Resistor
10 uF Electrolytic Capacitor - SEE ABOVE NOTE FIRST
5 pin Female Dupont Connector
REAN Stereo NYS231BG-LL Extra large entry 3.5mm Mini Jack plug


Connect as diagram with 3.5mm Jack TRS ;

Tip - Signal T
Ring - Signal R
Sleeve - Ground

Connect Veroboard as circuit diagram ;

PK-232 TNC connector ;

Pin 1 - RX Audio = Signal R
Pin 2 - TX Audio = Signal T
Pin 3 - N/C
Pin 4 - Gnd = Ground
Pin 5 - PTT = Via Veroboard circuit

AEA pin-out for PK-232


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