Ray,
That cable connects to a digirig, 
It's kind of same thing like a signal link. 
I believe it has all the circuitry for a PTT and other things. 

But it's a good idea what you're saying about bringing the power level up with a dummy load. 
Take a look at the link to see what I'm talking about.

https://digirig.net/product/digirig-mobile/



Best regards
Dave
KD2GIY

On Wed, May 27, 2026, 9:16 PM Ray Fantini <RAFANTINI@salisbury.edu> wrote:
A pin-to-pin cables are crap! No impedance match between high impedance output of computer and low input impedance of the radio. Also how are they attempting to do the PTT control?  Maybe they assume you're using VOX? That's always fun outside of the program, and the computer is making random noise. The general rule for proper ALC is to start with outgoing audio all the way down and start turning it up slowly to you see output power. Start out using a dummy load and power meter first!  Most digital jockeys tend to drive the crap out of the radio and introduce distortion.
I have bult several of these interfaces for use on GRC-106, Harris Falcon stuff and played around with it on your 70 without issues running both desktop and laptop systems. I use a 9-pin plug to an adapter with cables built up for the small microphone and large connectors on different radios.
The transformer is a Bogen WMT-1 available on eBay

Ray F/KA3EKH


From: mrca-bounces@mailman.qth.net <mrca-bounces@mailman.qth.net> on behalf of KD2GIY via MRCA <mrca@mailman.qth.net>
Sent: Wednesday, May 27, 2026 6:29 PM
To: MRCA <mrca@mailman.qth.net>
Subject: [MRCA] U-329 cable for digital work

Riddle me this? 
Has anyone tried these cables for the digi rig? 
If yes, what radio did you use it with and how did you monitor your ALC so the digital signal did not over modulate? 

https://digirig.net/product/u329-cable/



Best regards
Dave