#Ham radio speech recorder manual
#Ham radio speech recorder professional

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. 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. 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. 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).Įven though I’d do something impedance match wise, it’s not strictly necessary. 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 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. 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. 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. 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. 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.

#Ham radio speech recorder professional

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). 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. 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.

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. 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.

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.

#Ham radio speech recorder manual

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).