I think you want a "DJ splitter" cable. Typically a stereo (TRS) plug and two separate MONO output jacks, one for the left and one for the right channel. DJ's use one to monitor a track they are playing on one channel while cueing up a 2nd track in their headphones; the DJ software is configured to output to one track or the other. Use when you have a laptop or tablet with one audio output and don't want to or can't use a mixer or 2nd (USB?) audio device. Usually well-made because DJs hate equipment failures mid-gig. (and we hams hate equipment failures in mid-pass!) I have a Griffin DJ Cable and will have to test this myself. Native Instruments (Traktor) and other DJ equipment vendors sell these. $10-$12 give or take.
The use in this thread is to combine 2 signals into one input jack, while keeping them on separate tracks. Play the recording back in software like Audacity as suggested by others.
I agree the easiest approach is wire a cheap electret mic for local (Uplink) audio. If you tap audio from your uplink radio mic input, you may need to pad down the audio level to the recorder and take steps to isolate the recording line from the radio input.
The other "splitter" cable described connects left and right channels in parallel and is intended . Usually called a headphone audio splitter. You may get a mess unless you wire the plugs from your downlink and local audio to put signals on just one channel. More trouble than it is worth IMO. YMMV.
73 Steve KS1G
-----Original Message----- From: John Brier [mailto:johnbrier@gmail.com] Sent: Friday, May 18, 2018 10:52 PM To: Steve Kristoff Cc: AMSAT BB Subject: Re: [amsat-bb] Recording TX & RX from one or two radios?
Probably because I used the wrong term. It is a breakout cable. Here is what I have. Haven't used it yet, but it should work.
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73, John Brier KG4AKV