I am trying to work satellites with a handheld antenna and a Wouxon HT. Need to be able to record the QSOs because I don’t have enough hands to record callsigns.
You can do it in many ways, but easiest is to get a cheap earpiece, split the cable and send a ‘sniff’ of it to a portable recorder. Most of the zoom types are quite happy with their xlr pin 2 and 3 wired across the headphones and the level taken down with a pad. Depends on your equipment, but a simple split with battery kit seems by far the easiest.
The things you need to consider :-
If your record uses a mic level input, the earphone/headphone/aux speaker output is way too high level to pass straight into a mic input, so you’ll want to set the audio output (measured listening via a line-level input) and adjust radio side AG gain (volume) until the peaks do not exceed 1V peak to peak, slightly under is better - best done monitoring a fix level injected/received Sig modulated with a fixed test tone (if you look in a servicing manual for radio, it’ll quote an appropriate audio level reference for test tones).
Having got your receiver AF Gain/Volume setting, you then need to attenuate it to match the correct range for the mic input on recorder or not if using a line-level input.
It’s also worth noting there’s an argument that you should impedance match too, but getting the right appropriate levels is usually adequate and effective.
That’s how I pass line-level/active speaker level outputs from anything to mic level inputs when I need to record with limited resources. If I’m using serious kit, I pass the receiver output into an appropriate channel of a multi track recorder mixer section (using an MD era MT Tascam as a mixer, I feed the high level into a line level channel, if it’s a true earphone level output on receiver use an attenuated direct channel output intended for external MT recorder to feed a mic level input on digital recorder.
Note, level ranges from dynamic insert mics and capacitive insert mics (condenser/electret) and ribbon mics differ somewhat, so what actual attenuation you’ll need to feed a recorder mic input depends on era of recorder and it’s designed support for types of mics. Line level simply depends on if the line level input is built for consumer line level (1v peak to peak) or professional line level (has a higher peak level tolerance and different noise floor level in recording).
So, in short, headphones level to line can be done with a simple patch, just don’t overdrive the input else you’ll have compression and/or distortion problems. Passing headphone level output or higher into a mic level input is well into feeding a dog which will be well into the distortion and compressed end result territory without attenuation. Sure, turning the phones/active speaker output to just above mute level will work at a push, but the SNR will be ludicrously poor and definitely not lead to good recordings.
If my refs to AF Gain confuse, that’s what most serious comms receivers and transceivers refer to volume as, which is what I’m used to, so the reference stuck with me.
Awesome! Thanks guys for the input!
The important bit really, however you wire it up, is to ensure the peak level is matched to what the input can handle, so in the case of most pure digital voice recorders (which usually have an input intended for electret type ‘condensor’ element microphones), you’re talking attenuation from x V peak to peak audio feed from receiver (depends on what the output was built to drive) to x or 0.x type mV levels. It’s a bit like trying to feed the HiZ instrument input on a guitar amp with a line level or headphones level source. The actual attenuator is a scratch build affair easily built out of junk pull components (mostly resistors), and can (if you can use narrow enough resistors) fit inside a regular meyal or plastic film can type size (the kind 35mm film rolls came in).
Even though I’d do something impedance match wise, it’s not strictly necessary. You may find you’ll need to have a DC blocking capacitor on the attenuator output to block the phantom DC normally piped up the mic lead to drive non self-powered electret mics. Whilst the lack of won’t harm anything, you really want to block that DC as it can compromise the quality of what’s recorded. This blocking capacitor bit is usually part of the amp/matching circuit built into ‘active‘ mics (self powered type) where the phantom DC (where present at the mic input) isn’t used. You’ll be able to determine if you have a DC source in the mic input as it’ll show in a spectrogram of a recording. Some recorders allow you to shut off the phantom where not needed, so consult the manual for your recorder.
If you’re going to archive recordings, somewhere down the line, opt for a recording format combination (if compressed format) which has a sample rate suitable for a higher bandwidth than the audio range intended and a bit rate that favours long recording and good voice readability and clarity above anything else.
Again, out of preference, I’d employ (for compressed recording, out of necessity not choice) a sample rate a minimum of 4x the bandwidth of the audio range, but 2x will be nearly as good. But I’d normally record direct to lossless or uncompressed was and posted it compress to what suits the contents and intended post-edit use.
But that’s overkill for most people, so use what works for you.