Wednesday, December 15, 2004 Zulu
K2 PSK Cable

I made a PSK interface cable for my K2. I have a TigetTronics SL-1+ interface that I bought to replace a similar one I had constructed, but which had mechanical reliability problems. I had previously bought Don Wilhelm's Fixed Audio Out board, but wanted to see if I could get by with something simpler.

First I tried the AF IN on the Mic jack and AF Out from the headphone jack, but all the plugging and unplugging bothered me.

Next I tried Sverre Holm's suggestion to take the AF off of the audio gain pot through a 1K Ohm resistor. I found this worked but the audio level was low enough that I was losing signals.

Next I tried W4GS's suggestion of just taking the amplified output before it hits the headphone jack, as part of his fat wire PSK interface. I didn't like having to hook the mic jumper block on the control board over to the RF board, but with the Fixed Audio Out modification, I'd have to run 5 wires instead of just one, so I decided to go ahead and do that. I used a gold-plated pin connector which I trimmed on both sides, and then some insulated stranded wire (probably should have used Elecraft green standard!) and took it from R36 common to numbered side of pin 5.

The cable I made from a Cat 5 STP (shielded) cable which I cut off at one end. I used the shield wire for pin 8, which goes nowhere on the interface side. I used a signal ground for the other one (one connected to ground on the TigerTronics box) and then the appropriate AF IN and AF OUT wires from the connector. My choice of connections was determined by wanting to use the same TigerTronics configuration for the FT-817 cable, so I didn't get to optimize the twisted pair usage.

Anyway, it all appears to work. I get acceptable signal levels with acceptable sound levels from the speaker, and if I want to muffle it completely, I can plug in headphones or an unterminated headphone plug.

I'm keeping the W3FPR board unbuilt, in case I need it for some other reason, or become dissatisfied with this solution.

- posted by Leigh @ 07:13 z
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