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Convert the extension cb jack to line out audio

nomadradio

Analog Retentive
Apr 3, 2005
5,463
7,943
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Louisville, KY
www.nomadradio.com
Using an "aux" audio output, at a line level or line impedance is typically used to feed an audio recorder of some sort.

Trouble is, a recorder needs a predictable signal level, and a way to set that level so the recorder will be happy.

This means tapping into the receiver audio upstream from the volume control. An "aux" output is generally the same signal level regardless of volume setting.

And tapping in anywhere downstream of the volume control will have a level that depends on the setting of the volume control.

The impedance you want to feed into from this 'aux' output will matter. The higher it is, the easier this will be.

The Cobra 2000GTL has an output like this. The schematic shows TR51 as a buffer and impedance step-down amplifier driving the 'record' jack in that model. Would probably work if you copied it.

73
 

Techno1

New Member
Feb 21, 2022
19
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3
45
New Hampshire
I need something that will fit in an existing project box. Need it to be used on different radios so taping inside the radio is a good idea but cant do it that way. I do have the TR51 section and will study it to see if it will work.

thanks
 

nomadradio

Analog Retentive
Apr 3, 2005
5,463
7,943
573
Louisville, KY
www.nomadradio.com
Well there's your problem.

If you can't invade the radio to hook up ahead of the volume control, you'll be stuck with always compensating for where the volume control is set. Too much level will overdrive the recorder's input, sounding noisy and fuzzy. Not enough level will make it weak.

An external box that plugs into the external speaker socket? So you can use it with any radio you want?

You'll need an external speaker, just to start. Plug anything into the external socket and the internal speaker will be off.

Your "external recording box" will need a cord that plugs into the external socket, a socket to plug your external speaker into, a level control pot that feeds an output cable with whatever plug is needed on its far end.

Sounds like anyway. Would be simpler than tapping into the radio's insides. And getting the level set will matter a lot. Until someone changes the volume control setting, and you'll have to set it again.

73
 

Techno1

New Member
Feb 21, 2022
19
4
3
45
New Hampshire
Yes I know about the audio would have to be at a set level and if changed by the main audio knob chance of distortion. Its like the PP-1 20 second record boards on how they worked, the same way the record audio was controlled by the radio audio, a trial and error. Ill figure out something.
The record board I have is 8 channels and records up to 11 minutes. it has a mike in and line in it has a switch to go from mic to line in. But again if to much audio into the line in audio is not good..

thanks for some info
 

Techno1

New Member
Feb 21, 2022
19
4
3
45
New Hampshire
No this is a special made board with 8 channels and 11 minutes record time so you can record the 8 channels or do a complete 11 minute record and has erase and other features just trying to make a watergate box, the mic sounds great just need to get the line audio in correct.
So you can use 2 channels to record and the other 6 for noise toy sounds or whatever you like and I have it set to keyup when mic is keyed.
8 channel rotary selector.

The pp-1 only did 20 seconds per board
 

hpssb

Active Member
Feb 9, 2014
59
55
28
Kalgoorlie, WA
We had a couple of these boards made a few years back, about 1.5 inch square and goes inside the radio. One on a cybernet base and another on a cobra 148 side mike mobile. In both cases an extra 3.5mm stereo jack was added to give line out. Doesnt matter where the volume is set, the line out level stays the same.

I use a Zoom H1 digital recorder set to line in with a stereo 3.5mm patch cord to the radio. An 8 gig card gives about 20 hours of recording at near cd quality, when done upload to pc and edit in audacity.
 

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Techno1

New Member
Feb 21, 2022
19
4
3
45
New Hampshire
Well i think I found something that might work its a speaker to line/rca output.
Has 2 channel only need 1 channel and has transformers built in. Suppose to take speaker level and drop to rca level so you can add an amp to the adapter. Ships from China so should get around July 25th. Hope it will do the job at least get some good recording audio. Also is adjustible. Cheap $1.40 plus shipping so i ordered 10 pcsScreenshot_2.jpg
 
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