Sharing Headphones between two rigs fails.

[KB1NGQ]

I wanted to share one set of headphones between two rigs (Kenwood TM-241 and IC-718) via an "A/B" audio switch. There seems to be no problem on the TM241 side but, when I switch the A/B switch to the IC-718 "phone" output side and hit the PTT I hear myself (i.e. it does not cut out the audio feeding the headphones). If I disconnect the phone out feed to the A/B box from the Kenwood, or if I disconnect the pwr feed (feeds to both rigs from a "Rigrunner") the PTT cuts off my audio on TX to the headset as it should. The TM-241 does not have to be turned on to cause the problem and disconnecting just the ground or the power to the TM-241 fails to eliminate the problem. Both power and ground, or the phone connection has to be disconnected from the TM-241. Also, with common ground from all equipment to external ground rod, disconnecting any or all grounds has no effect on the problem. Ideas? KB1NGQ

[K2QI]

Can't you just use a 1/4" Y-splitter?

[KB1NGQ]

K2QI,

I'd thought of that but I don't see how that would actually "switch" between the audio from one rig to another and that was the point. During SET's/Drills I'm often trying to monitor 2m and HF but when I need to copy messages, I need to hear and talk on one rig. I'd thought a simple A/B "A/V" switch, using just one side of the stereo would work. Not! However, I gave up on the A/B switch and did quick and dirty jumper connections to a DPDT switch that completely isolates the feed and ground from either "phone out" from each rig. Problem solved! Apparently, the IC-718 does not like sharing the phone out ground with the TM-241. I'm not quite sure why. Maybe the tied A/B box ground is providing a path that disables the PTT's ground(?) ability to cut out the TX audio back to the phones. I'd like to really know why it doesn't work but, for now the A/B box goes back to the store and I'll build a small box with the DPDT switch with the needed I/O connections. The mess of alligator clips and wires on the bench are completely unacceptable. Thanks for the reply. KB1NGQ

[K2QI]

I'm sorry - I misread your first post. I thought you were trying to share one rig between two headsets.

[KB1NGQ]

K2QI,

Understood. Thanks for the thought. KB1NGQ

[K2QI]

Posting on QRZ while working, and on one hour of sleep, can be embarassing... lol

Anyway, in my haze I'm thinking of something involving a relay and closed loop between two jacks that switches in the presence of voltage. Key rig A, and the relay completes the audio circuit for rig A. Release the key, and relay goes back to ground or null. Key rig B, and the relay completes the audio circuit for rig B. This way one when rig is keyed, the other is completely isolated.

[KC9GVB]

Wouldn't an inexpensive passive audio mixer work, such as the type used for professional audio?

[G0GQK]

You can buy some good headphones over here for about a fiver, try buying another headset ! Are they really that expensive in the US ? Go on ! Getcha hand in yer pocket !

G0GQK

[W4PG]

You might try one of these!

[K2QI]

You might try one of these!

Ding! Ding! Ding! We have a winner!