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Jwhipple
| | Posted on Monday, July 22, 2002 - 8:48 am: | 
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I have access to a decent stock of military surplus (brand new) Motorola mobile radio microphones for about $5 each.. They have 4 pins in the cable and would appear to be easy to wire up for CB use. Has anyone done something like this before? Any idea of what kind of quality sound I could expect? I don't need a power mic - just something to replace my stock mic, and am familiar with the quality of Motorola's communications equipment, not to mention how rugged their stuff is.
Any feedback?
Thanks! |
Highlander
| | Posted on Monday, July 22, 2002 - 2:19 pm: |
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Buy up the lot and Ebay 'em!! |
Jwhipple
| | Posted on Monday, July 22, 2002 - 4:24 pm: |
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Would love to buy up the lot of em and wire em up for CB/Ham use if I knew they would work! Don't want to waste my time and money if I know for sure they won't work, but I think anyone who has dealt with motorola's 2-way radios can agree, their stuff is hard to beat! |
Ss8541
| | Posted on Tuesday, July 23, 2002 - 12:08 am: |
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are you talking about the old 'big' round socket 4 pins?? if so, yes they will work. i can check one tomorrow(if i remember) and tell what the pin out is. then you'll know how to wire it for cb. to let you know how good they are, the majority of the ones in use are older than i am(25). the mic cord, may have been changed, but the 'palm' mic is still the same one that came with the 25+yr old radios. |
Jwhipple
| | Posted on Tuesday, July 23, 2002 - 7:27 am: |
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Actually you have the right ones in mind but I should have said that it has a 4 wire cord attached , no connector on it at all though. |
Jwhipple
| | Posted on Tuesday, July 23, 2002 - 7:27 am: |
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Actually you have the right ones in mind but I should have said that it has a 4 wire cord attached , no connector on it at all though. |
Ss8541
| | Posted on Tuesday, July 23, 2002 - 7:49 pm: |
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i have to correct myself. this mic will not work with electronically switched radios. it is used with relay relay switched radios. it will key the txer and work on rx(since rx does not have to be gnded) on the galaxy's and their clones, but the audio line most likely will not work since it needs voltage that the galaxys, cobras, unidens, etc do not produce.
i had to recheck the service manual for the radios that these mics go to today. it has been a while since we have had one of these dinosaurs in the shop, so i was a little rusty on their tx/rx switching scheme. anyway, here is your info.
red is mic hi/mic audio
blk is mic low/audio shield
green is the ptt line to the relay
wht is gnd |
2600
| | Posted on Wednesday, July 24, 2002 - 12:29 am: |
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I've been using Motorola TMN4001/4002 mikes two ways (no pun intended) on my Turbo and 2950: First off, unplug the mike from the radio you want to use. If it still receives without the mike, that radio will work for this trick. If the radio ONLY receives with the mike plugged in, forget it, or install a Roger Beep board that has a relay on it. THEN the radio will receive with NO mike plugged in.
The catch is that most of these mikes have transistorized replacements for the carbon element that Motorola used until the 60's. The audio wire carries POWER up to the amplifier inside the cartridge, and AUDIO back down the SAME wire into the radio.
The first way is to install the power for the cartridge inside the radio. I used a toggle switch added on the front panel to switch this off (it gives a straight mike a headache). Connect a 2.2k 1/4 watt resistor to the REGULATED 8 volts, the other end to the + end of a 10UF electrolytic capacitor, the negative end to ground close to the mike amp section of the radio circuit board. Disconnect the audio wire inside the radio from the audio pin of the mike socket, and insert a 4.7uf electrolytic cap with the + end to the mike socket pin, the - end to the wire you just took loose. A second 2.2k resistor goes from the first resistor/cap junction to the mike jack audio pin. This feeds FILTERED power onto the mike audio pin. The 4.7uf cap isolates this power from the mike circuit inside the radio, but passes the mike audio along.
The second way is pretty ugly: a 9-volt battery taped to the back of the mike, wires through a hole in the rear of the mike housing. If the mike has only a single-section switch, you will have to either stack on a second contact cannibalized from another mike, or find one that came with a 2-section switch. The black wire from the battery goes to ground inside the mike. The hot lead from the from mike cartridge goes to one side of the second PTT switch contact. A 4.7k resistor from the positive battery wire to the OTHER side of the second switch section, and a 4.7uf electrolytic goes from the audio wire of the mike cord to this side of the second switch section. (The FIRST section of the PTT switch is already hooked to the transmit wire, right?) How you attach the battery to the back of the mike housing is the really ugly part. I use 2-inch wide black electrical tape. A bracket might be better.
There is probably room to play with both the resistor and capacitor values to affect the tone quality, but these worked pretty well the first time, and I never got around to 'optimizing' anything about them.
Unless your mike got dropped on its head too many times, or was left out in the rain, these are LOUD, mean-sounding power mikes. A radio that does not have a mike gain control will probably hear the crickets in your neighbor's yard when you pause between words. None of the mikes I have are noise-cancelling, and will pick up as much mobile road noise as any other power mike if the mike gain is set too high.
They do seem to be much less likely to squeal when an amplifier is in use than the CB-type power mikes, but if you get large enough, or have ground problems, funny noises in the mike audio are still a risk.
73 |
Jwhipple
| | Posted on Wednesday, July 24, 2002 - 8:04 am: |
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OK here's the scoop - I found the model number of these mics, AND I found some pics of this particular model along with the connector.. I was wrong in my earlier post - these DO have a connector on them, but it is what appears to be a 5 pin male connector.
The model number is NMN 6032A. Maybe these pics will give us a better idea of exactly what we are dealing with... If the picture doesn't come up quickly , give it time, my server isn't the quickest in the world.
Check them out, I put them on my web server.
Http://www.freebander.d2g.com/mic1.jpg
http://www.freebander.d2g.com/mic2.jpg
Thanks again!
Jon |
Ss8541
| | Posted on Wednesday, July 24, 2002 - 10:09 pm: |
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chris(2600) i think the mics you listed are the same as the tmn6013a for the mocom-70. those are the ones that i am looking at. the mics that jwhipple shows, look like the ones that go to the maxar80 line of radios. i'm not exactly sure how those work either, but i can find out tomorrow by looking at the service manual. i don't see many of either as they are b4 my time. the ones that i have seen, the mic and tx/rx swithching circuit was never the problem. and the ones that are still around and working, well they work just like the day they were made.
as for the modification, that was nice. i knew from looking at the circuitry that they could be 'converted' but i didn't want to tell jwhipple that without a 'proven' way, and he, or someone else, end up burning up a radio or two with the trial and error methods of 'designing'. i made a copy of your modification for myself. |
Jwhipple
| | Posted on Wednesday, July 24, 2002 - 10:39 pm: |
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I appreciate the consideration , SS8541! Whatever mic I go with will be hooked onto my 2950 - and lord knows I don't want to fry that puppy! I also appreciate the time you two are taking to share the info, lord knows that I never would have had the resources available to me to get this working without good solid info!
Thanks again!
Jon |
2600
| | Posted on Thursday, July 25, 2002 - 11:23 pm: |
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I may stir up a can of worms with this addition, but if you use a power mike with a RCI 29x0 radio, its REALLY a good idea to leave Q32 where it is, unmolested. Yeah, if you want the AM audio "wide open" you can pull Q53. This shuts down the AM limiter ONLY, leaving you a functional ALC for SSB transmit. SSB really NEEDS the ALC to stay readable without having to "play" the mike gain "like a violin". It seems like everybody on the internet has a favorite reason to pull Q32, or lift one leg, or insert a resistor into it.
Q32 in fact has THREE functions: you already know the AM limiter (AMC) and SSB limiter (ALC) feed to it, but a third control voltage provides COMPRESSION, keeping the audio chip that FEEDS into the AM and SSB limiters below the clipping point. Sure the AM is louder when the AM MODULATOR itself is clipping, and the mike amp chip has enough output to drive it that hard, but it really sounds better when the audio feeding INTO the AM modulator is still clean and unclipped. I didn't think of this little detail until I checked back in tonight. Molesting or pulling Q32 is such a widespread piece of advice, I felt I should add my 2 cents on that forgotten detail.
I looked at your pictures, and it sure LOOKS like the same thing. I quit doing FM land mobile radio work 12, uhh, 13?, (maybe more) years ago, so I am completely out of date on that stuff now. The mikes I have must be 20 years old or more, about as outdated as my skills with the stuff.
73 |
Jwhipple
| | Posted on Friday, July 26, 2002 - 7:29 am: |
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Clipping anything in the radio is not an option for me, PERIOD... |
Ss8541
| | Posted on Friday, July 26, 2002 - 11:11 pm: |
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jwhipple, i forgot to check out the mic you listed, but i will get around to it. my gut feeling is that is the same mic(looks the same) as the 4 wire but with 5 wires here. i'll get the wire 'code' for you next week.
and 2600, you mention that when using a power mic it is best to leave q32 unmolested. i have one change to this. when using -any- mic it is best to leave q32 unmolested(all the way down to adding a resistor, which i know one place you saw this even though i am against that). |
Tech181
| | Posted on Saturday, July 27, 2002 - 12:29 am: |
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Jwhipple,
A little off subject here but what brand and spec of camera did you use to take those pics of the microphone on your website. They are very, very good.
Steve
Tech181
Tech181@copperelectronics.com |
Jwhipple
| | Posted on Saturday, July 27, 2002 - 7:15 am: |
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Actually I didn't take them myself, I found those out on the web somewhere after a lot of digging once I found out the model number.. |
Rightwing
| | Posted on Sunday, January 26, 2003 - 2:18 am: |
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i recently picked up a motorola handheld mike , and i plan to use it on my ranger. the wiring code was the same as ss 8541 siad and everything. the only difference is that instead of a 9 volt hanging out, i decided to use a smaller battery like a car alarm 12volt or a 7 volt battery ,which would fit inside easily in the mike with a little foam so it wont jingle around and a round battery holder the type that astatic and some others used to use in their power mikes.im leaning on getting a car alarm 12 volt battery as they are cheap and do work. an ntype battery connector can be used also. any feedback? i have a base version of motorolas mike and i had it retrofitted internally with a 9 volt and man does it amplify! i put in a 47 k resistor in the audio line so i could run my mike gain wide open and not overmodulate. as someone posted ,these mikes are loud. by the way the small car alarm batteries are about $1.50 around here and 8.95 for 7 volt batteries and thats why im leaning towards a 12 volt..any comments would be appreciated. |
2600
| | Posted on Sunday, January 26, 2003 - 5:55 pm: |
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Hey Rightwing,
12 Volts should work. Using a higher value resistor may be necessary, say 3.3k or 4.7k. The two 2.2k resistors in the setup above seem to work well for 8Volts/9Volts. At least it will fit inside the thing.
73 |
Rightwing
| | Posted on Sunday, January 26, 2003 - 11:44 pm: |
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thanks, i`ll try hooking up a 3.3 or 4.7k and see if it does good. im gonna see if a 1/4 resistor will do the trick . only reason i chose the 47k resisitor was that in the base mike it cut the squeal and now i can run the mike gain on the ar-3300 wide opennnow without worrying.incidently if a 1/4 resistors too big im sure a 1/8 watt will do. |
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