CB Mic wiring for UK FM radios

I'm often asked how a particular mike is wired to a particular radio. Do yourself a google search for a microphone pinout chart. I typed in "UK CB microphone wiring" & quite a few popped up. The chart will tell you which pin TX, RX, Audio & Screen go to.
This video will help you wire an unknown microphone with some simple tests & basic knowledge as to how the mikes work.
Get yourself some kind of test meter with ohms or continuity. you only need something cheap & cheerful for this & a quick Ebay search for "multimeter" soon spotted one delivered for just £3.39.
Recorded 23rd December 2020
Richard G0OJF
Lincolnshire, UK

[@SentinelOneLove]

Brilliant content.. Came across this vid and brought back memories from collage then Am CB from 30 odd years ago.

[@eduardosanchez6665]

Muchas gracias por tu explicación , pude componer mi micrófono, gracias y saludos desde Veracruz México

[@freedomvigilant1234]

That was a highly informative video. I think I will have to find the article you wrote. :)

[@eddywiggins620]

Knights use to do a very comprehensive mic wiring book back in the 90's which had in it what you went through for determining cables. In Northampton, we breakers who can't get their head around that the mic cables have different colours and what's colour is used for function in one mike is possibly different in another. Especially when you get 5 and 6 pins as the norm on today's uk legal radios. Mics are my fave at playing with, from the std mic to basic power mike to the more comprehensive mics with power echo.

[@mikerim6861]

Don’t know about you but every time I wire a mic up I tell myself I’m gonna buy one of those mini vice things to hold the damn plug steady 🤣

[@ukfmcbradioservicingTango21]

Right that does it! I've been meaning to make a mic wiring jig for 38 years. I'll get Mr Chippie to make one on a video....he should get back here after his Christmas trip back home this evening. We've got a small vice but rarely use it for wiring mikes. Richard, G0OJF, UK

[@mikerim6861]

@@ukfmcbradioservicingTango21 Look forward to watching 🤣 might give me inspiration

[@HughJarse1968]

Excellent tutorial, Richard, thank you very much indeed.

[@pgmilling]

Wow, that was a lesson I enjoyed Thank you.

[@ukfmcbradioservicingTango21]

Glad it was helpful! Richard

[@yorkshirebikerbitsnbobs]

Hi Richard.. Just wanted to mention with regards to your flat screen... There a plenty of HDMI flat panels out there with a fantastic viewing angle... I can stand at the side of my TV and still see the picture clearly... Others can be awful though... Probably worth a test before you buy.

[@jameslangdon10]

I have looked for your article but can not find. Do you have a link please. Very good video, learnt a great deal

[@ukfmcbradioservicingTango21]

Hello James, this link will take you to the correct magazine. worldradiohistory.com/Archive-CB-Radio/Citizens-Band/CB-Citizens-Band-1988-10.pdf Richard

[@HughJarse1968]

I know you aren’t keen on power mics, Richard, but can you tell me whether they’re wired the same way as the basic mics? Does the variable control on the mic affect the level of the output audio signal? I have a Spyder power mic eBay purchase and am wondering how to wire it for Cybernet radios. Many thanks :)

[@ukfmcbradioservicingTango21]

They do wire the same & yes the variable volume control affects the output level. Sometimes power mikes have more wires so they work with old American valved sets with relay switching. I accept that some people like to use a base station microphone with a base station. My objection (other than echoes) is that UK FM radios all incorporate speech processing circuits & usually sound their best with a standard microphone. If you add pre-amplification with a power mic, the speech processing in the radio can end up adding distortion. Back to the USA AM system. speech processing wasn't part of the type approval & getting modulation clear & closest to 95% modulation helps with clarity & thus range. On an FM system range isn't affected by the audio...unless it's muffled. Therefore the whole accessory mic market is aimed at the USA or other AM CB markets. On the post 2014 CE approved radios that have come here & are useable legally on AM (on the CEPT 40 channels), they all have speech processing because they are AM/FM, thus making power mics pointless. Richard, G0OJF, UK

[@MrPaul42u]

Hi Richard, great video. Can I make one comment as a complete novice myself, it would be helpful to make sure whatever you are working on or describing, is always within camera shot.

[@ukfmcbradioservicingTango21]

It's a snag which is being rectified. When I had a new video mixer a few months ago, the monitor output is HDMI; I was previously using Sony Broadcast kit, but youtube didn't recognise the HiBand format & compressed the hell out of everything to 320p. So with the new mixer I can't use the mega quality sony CRT monitors, so had to buy a flat screen one that accepts an HDMI input.........but the flat screen doesn't have sufficient viewing angle to be seen from my seating position at the bench. I have therefore ordered a small HDMI monitor to put on the bench to overcome the problem. The monitor arrived yesterday but I'm still waiting for an interconnecting cable to arrive. Richard

[@sanjayadulankateamlead-tra5874]

Do you have the schematics/wiring diagram of a Maxon PM150 compatible microphone?

[@BoB4jjjjs]

Your drawing might have been a little better, but you explanation was fine. It might appear complicated if someone has never fitted a plug to a mic before, but it really is easy. Learning to solder is a bit harder, but heat what you are soldering and add the solder to it, NOT the solder to the iron and try to flow it onto the wire or pin you are trying to solder. Might appear obvious to most people, but it would surprise you how often I see this being done. Always tin the components with solder, then join them together the quicker you learn to join both parts together the better. All it is is practice. The 5 pin din plug is not an easy plug for a beginner. Wiring is here www.radiomicwiring.co.uk/ Click on the name of the CB to get detailed wiring. I have NOT checked they are all correct.

[@stevelomas4119]

Hi Richard hope you can give me advice on a problem I have, I have in my collection a nice example of an LCL 2740 which needs a new mic, I've purchased the new mic which is similar to the ones you use and the 5 pin Din plug...here's my problem, on every wiring diagram I can find it says it should be wired up thus...Pin1 Audio, Pin 2 Screen & Pin 3 Transmit...where does the Receive wire go? My head is scratchier than a well known corner trying to work this one out...any ideas...thanks. Steve.

[@ukfmcbradioservicingTango21]

So I looked at the circuit. Correct 1= Audio 2= Gnd 3= TX. The radio uses a relay to switch between TX & RX, so no RX connection to the mic is required. Incidentally, pin 5 is power out to a mic that requires a power supply such as a K40. This means the radio receives with no mike connected. Richard

[@stevelomas4119]

@@ukfmcbradioservicingTango21 Thanks for your quick reply...so I can just stick some shrink tubing over the end of the RX wire and not connect ? All the best and have a nice Christmas. Steve. 🥂

[@ukfmcbradioservicingTango21]

@@stevelomas4119 Roger on that. Richard

[@ryandys8217]

Hello. I am trying to put one of these mics on a kenwood 281 that has a rj45 jack. I can get the radio to key up but i dont get any audio out in the air. Could you please help me?

[@ukfmcbradioservicingTango21]

I'm sorry Ryan but I can't help at all. Quite a few business radios we service use those kind of modular plugs. We either repair the mike with the set & if it's the lead that's duff or no mike at all we would then either buy a new factory mike or a new cheaper pretend mike depending on what the customer wants. I haven't ever owned any Kenwood/Icom/Yaesu amateur radio gear & we don't normally do repairs to amateur radio equipment either, so I just don't see radios like yours. Whichever wire carries the mic audio will have to be the screened one. If the lead you are using isn't screened..such as a telephone type lead, you would lose the audio in the lead & end up with just a hum, I would expecr. Richard, G0OJF, UK

[@ryandys8217]

Maybe thats why im getting no audio out. I was using just standard wire not screened for testing purpose.

[@trx250rpuma4]

Hi mate when I key up my mic sounds like there's wind in the back ground what could this be

[@ukfmcbradioservicingTango21]

You have to work out if it's the radio or microphone at fault first, so try another mike. If it's the microphone, then that sort of noise is a) the mike lead or b) dirty switch. It's easiest to use a switch cleaner first. If you are in the UK, the Servisol one is the market leader. Richard, G0OJF, UK

[@bigpimp347]

it's a shame there's no generic standard wiring. we know braid is ground. but lots use red as RX black as TX and what ever is left, yellow or white is audio. but even you can never be certain.