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Old December 27th, 2006, 03:22 PM   #1
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How to capture 2-way radio traffic

I need to capture some live radio traffic for a production (airband). What I've tried before - with horrible results - was using the earplug connection from my Sony scanner to an adapter that went directly into the camera XLR input. There must have been a slight impedance mismatch or something because the captured audio was not at all clean - and I'm not talking about the normal background noise that comes from 2-way radio communications.

What is the best way to capture 2-way radio traffic into the camera - or other recording device. (the audio is not being synched to any live action, it's for SFX).
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Old December 27th, 2006, 03:58 PM   #2
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My first guess would be that the scanner's headphone output is too high a level and overloading the input you're feeding. It's absolutely too hot to feed a mic level and probably most line level inputs as well. Just backing off the volume control isn't going to cut it, the difference between completely shut off and too hot is just too small. Hi thee over to Radio Snak and pick up an attenuating patch cable for a couple of bucks.

Because a lot of the characteristic tonal qualities we associate with communications radios is due to the speakers they use, another alternative would be to put a mic a few inches in front of the speaker aimed at the centre of the cone and record the sound that way. That would probably give you more realistic tonality, nicer squelch tails, etc
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Old December 27th, 2006, 04:16 PM   #3
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It might help to feed the scanner output into a decent set of closed headphones and put a good lav in one of the cans.
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Old December 27th, 2006, 04:34 PM   #4
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I'll have to check, but I'm sure we did use an attenuating patch cable; we still got a lot of background hiss that wasn't there when normal headphones were plugged in, giving me the impression of impedance mismatch.

The idea of a mic in front of a speaker or inside headphones won't work because in order to get a strong radio signal means we're in an environment that has too much ambient/exterior noise to make for a clean capture.

All too often I hear 2-way traffic that's been captured cleanly; COPS is a good example and so is a recent Discovery production about carrier air-ops - both had superb radio traffic grabs.

Maybe what I need is a radio that has more than just a headphone jack for an output source. (?)
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Old December 27th, 2006, 04:37 PM   #5
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The best way to do that is to use a scanner that has a "tape out" or line out. Most Uniden mobile scanners have a tape recorder output. Another way would be to tap into the line level signal inside the Sony scanner. You'll need the schematics and a soldering iron. Essentially you'd be bypassing the internal headphone preamp. I did this on a Yaesu VX-7R and the audio is pretty good.

Handheld scanners/receivers usually have a headphones only output, unless it's a specialty receiver like the AOR 8200, for example.

Anyway, if you need this for sound effects only, and it doesn't matter what the content of the radio traffic is, you might want to check out some live online Air Traffic Control feeds at LiveATC.net.
They also have an mp3 archive of those feeds. That'll save you the trouble of having to record a live feed.

Finally, I Just wanted to say, good luck! We're all counting on you.


Edit: Added picture of the back of a Uniden 780. Note the "Tape Out" jack.
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Old December 27th, 2006, 04:52 PM   #6
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Take the earphone out of the radio and plug in into the line-in (NOT mic-in) port of any computer or laptop.

Use a free program like Audacity (http://audacity.sourceforge.net - works on Mac or Windows) to record and edit the sound, saving as a standard .wav on PC/.aiff on Mac file.
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Old December 27th, 2006, 09:49 PM   #7
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I think that's exactly what we need, Adam. So now I just need to find a scanner with the air-band freqs and those outputs and we should be set!
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Old December 28th, 2006, 01:44 AM   #8
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Another approach

Robert,

I note you're here in Scottsdale.

Depending on the audio chain you're using, you might need nothing more than a simple audio pad. If you drop me an email, I could likely help you out.

Drop me a line.
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