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Author Topic: CB microphone pin out  (Read 9131 times)

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CB microphone pin out
« on: March 08, 2007, 02:42:23 AM »

http://i32.photobucket.com/albums/d11/uncle_stutner/d104mic.jpg

I have a microphone identical to this picture. I think it was used for CB radio or something similar, maybe shortwave. Someone, who heard I "liked microphones", gave it to me.

It has a 4 pin mini xlr looking connection on the end of it's cable. Is anyone familiar with this style of microphone device? I was hoping to use it as a talkback mic. It has a long bar on the side, which I would like to be able to use, when I wish to talk back.

What exactly is coming out of this miniature 4 pin female xlr connector?
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Nyquist

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Re: CB microphone pin out
« Reply #1 on: March 08, 2007, 05:17:12 AM »

Wow.

That's an Astatic D104-xxx ("xxx" signifying the model number of the base, of which there were a few varieties).  Definitely one of the classic transceiver microphones of all time, now sadly discontinued. I still have a handheld version of it (D104-M6B) stored somewhere.  It's a transistor powered mic (built in amp, 2N2712s I think), runs off a 9V battery, should be a volume control somewhere.  Early versions used a Hi-Z crystal element, changing to ceramic later in production.  The connector and pinout will be dependent on what model radio the mic was last used with, but essentially there will be a ground line, a PTT (push-to-talk) line and an audio line that you can adapt to your application, just cut the old connector off and rewire.  

Sometimes, the schematic was glued inside the bottom cover of the base...remove the bottom and hopefully you'll get lucky.  No doubt you'll have to change the battery anyway.

Keep in mind, the D104 crystal elements were sensitive to shock and heat, so it may be hit or miss.  Let me know if you end up giving up on it, but I do hope you can get it working.  Ballsy output, will certainly command attention as a talkback.

Better yet, buy a 2/10/11 meter radio and strap that thing on the front end.  "Goooood morning Vietnaaaam...!"

Quote:

I have a microphone identical to this picture.


Got a pic of the "real" one?

-- Robbie
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Re: CB microphone pin out
« Reply #2 on: March 08, 2007, 06:30:22 AM »

Mine has a "push to talk" lever on the side as well as on the base.

Here is a crude picture taken with my mobile:

http://i32.photobucket.com/albums/d11/uncle_stutner/d104.jpg

I removed the bottom and sure enough, there is the schem for the circuit! What a blessing! If 1/4 of the older equipment I came across had a schem printed somewhere on the chassis of the device, instead of the service manual, life would be much easier!

This is an Astatic D-104. There is a sticker on the base that labels it as "T-UP9 Stand". There is a sticker on the ceiling of the microphone that says "Mod NO D-104". It is in immaculate shape. How old do you think it is?

Is this mic of real value? Would someone out there in the world be hurt if they knew it was being cannibalized and used as a talkback mic?
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ssltech

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Re: CB microphone pin out
« Reply #3 on: March 08, 2007, 10:34:59 AM »

Usually the 4 pins on those connectors are 2 for signal (unbalanced) and 2 for contact closure (PTT-normally-open)

I'm sure that the pinout is somewhere on the web... but I didn't see it on a quick search... I did opnce build a few "roger-bleep" boxes in about 1981, when they launcehd citizen's band radio in the UK... Basically it was a box which watched the contact closure, fired a relay to hold on for a fraction of a second longer after release, and injected a 'beep' to indicate that the speaker had let go... (for the idiots who couldn't figure it out for themselves... or for people who wanted to sound like astronauts! Very Happy)

Anyhow, if it follows the standard passive mic pinout, you can measure the connector to discover which two pins give continuity when the switch closes. The Other two will therefore be the mic signal. One way round should be noisy, the other will be right.

Is this one powered by an internal battery?

Keith
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MDM (maxdimario) wrote on Fri, 16 November 2007 21:36

I have the feeling that I have more experience in my little finger than you do in your whole body about audio electronics..

Larrchild

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Re: CB microphone pin out
« Reply #4 on: March 08, 2007, 11:43:37 AM »

There is possible a switch inside labeled "E" and "R" switching.

When the switch is in "E" or electronic switching, the shield is common and red to shield keys the radio ..black to shield (NC) puts it in receive.

In the "R" or relay switching mode, I think red and black get closed to "transmit"  either way..  white is mic audio hot, and the rest are ground and keying.

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Larry Janus
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Re: CB microphone pin out
« Reply #5 on: March 08, 2007, 12:54:07 PM »

Yeah, it's powered by an internal battery.

The schematic on the inside shows the pinout for the attached cable. In addition to that, though, there are instructions on where to tap into the board to get a passive, or "always on", cold and hot connection out of it.
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Nyquist

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Re: CB microphone pin out
« Reply #6 on: March 08, 2007, 01:33:10 PM »

Found it.

 Schematics for the various D104 bases.

Don't think they're too valuable just yet (about $100 USD still from what I can find) but they will likely become more so as time goes on.  There were a variety of finishes as well (the "Silver Eagle", "Golden Eagle") for the more fashionably conscious radio enthusiasts, which probably have a slightly higher value. As far as I know, they were still in production until just a few years ago, so hard to gauge what vintage yours might be.

Seems a shame to relegate it to TB duty, and a bit unwieldy as well. But unless you're willing to adopt a new money-sucking hobby (note: "CB" = "constantly buying"), might as well use it for something.
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