Charlie Tango 11m DX Radio Group Forum
Would you like to react to this message? Create an account in a few clicks or log in to continue.


Welcome to the Charlie Tango DX Group. The home of ALL things Radio - CB, 11m DX, Amateur, PMR446, PLD, Network and Data. We welcome all radio enthusiasts of all knowledge levels. Join today and claim your own unique World Famous CT Call-sign
 
HomeEventsCalendarFAQSearchRegisterLog in
XMAS COMPETITION: Win a Brand New Yaesu ft891 with Wideband Modification and to help the winner use it we are including a 30 Amp Power Supply on top. This is our biggest prize yet. All this could be yours for Christmas for just £20. - See Latest News Forum for details.
Latest Buxton 2020 News: Unfortunately, due to the Covid-19 pandemic we have had to cancel this year's Buxton date. Sorry for any inconvenience.
Navigation
Useful Radio Sites
Log in
Username:
Password:
Log in automatically: 
:: I forgot my password
CT Bill Board





Views This Year
All Time Views
Classified Adverts

Latest topics
» Coax i am using 213
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 4:23 pm by NUBSTER

» 11m conditions
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 3:02 pm by NUBSTER

» Was the C&G RAE easier than today’s amateur radio exams?
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 12:14 pm by Alan Pilot

» introduction/call sign request
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 12:01 pm by Fa7errider44

» call sign request
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 11:27 am by Lloyd

» Call sign request (Issued)
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 11:10 am by Tony Curtis

» Call sign request (Issued)
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 11:09 am by Tony Curtis

» Trips Down Memory Lane
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 10:24 am by NUBSTER

» Bending a Mobile Whip Antenna
Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeToday at 6:19 am by Alan Pilot

Keywords
frequency Mobile callsign bazooka alan Mckinley tango radio ss9900 chart call ss6900n Sirio 9900 president Calling tickets lincoln charlie antenna sign list Baofeng midland power division
QRZ Database
 

 Impedance of mic for tti TCB-550 (AMC-5011)?

Go down 
AuthorMessage
MadHax
New Member
New Member
MadHax

Call Sign : 68-CT-059
Posts : 6
Times Thanked : 1
Join date : 2020-07-10
QTH or Location : Jordanstown
Equipment Used : None, researching it.

Impedance of mic for tti TCB-550 (AMC-5011)? Empty
PostSubject: Impedance of mic for tti TCB-550 (AMC-5011)?   Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeWed Jul 22, 2020 7:26 pm

Hey guys, can anyone tell me the impedance of the above mic for the TCB-550.  I have a mic (not the original) but it is about 470R, and can't get any modulation on a rig check, so i think I should be using a mic with a lower impedance, say 50R?  Can anyone confirm or otherwise?

K
Back to top Go down
View user profile
Victor
CT Directors
CT Directors
Victor

Call Sign : 26-CT-3228 Ham M7VIC
Posts : 1010
Times Thanked : 63
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

Impedance of mic for tti TCB-550 (AMC-5011)? Empty
PostSubject: Re: Impedance of mic for tti TCB-550 (AMC-5011)?   Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeWed Jul 22, 2020 8:49 pm

Hi Keith,

(Public health warning.... I'm gonna waffle, but it may help others as well Smile)


A typical radio microphone is a 'Low Z' device, which basically means low impedance and that equates to 600 ohm or less.
Most CB microphones I've seen run from about 150 ohm up to the 600 ohm mark so would've thought your 470 ohm sits about right.

The service manual is available from ManualLibs and checking the schematic shows a standard affair mic input circuitry, good for most mics including power mics.

Luckily this radio isn't one of the types with 'phantom power', or in most CB radio terms, one that carries 13.8 volts on a pin ready to damage the radio should you inadvertently wire it incorrectly!

A microphone seems the easiest thing to change or 'upgrade' on a CB and is done often, sometimes with disastrous results.

But, that said, the commonest problems I've seen over the years is dropping the damn things Wink

We forget how well these little devices convert moving air pressure from our mouth into an electrical signal for the radio....it's actually quite a delicate device(!) In which case I'd be suss about any second hand microphone, (let alone the fact it's usually full of someone's elses spittle!!! Yuck!)

If dropped at some time it could be completely useless but still measure a typical resistance on the element.


Replacement mics are cheap enough and it's always worth while getting a new one. At least if you drop it, you've only got yourself to blame Smile


Anyway, waffle over....I hope that helps you out somewhat.

All the best,
Victor
Back to top Go down
View user profile
MadHax
New Member
New Member
MadHax

Call Sign : 68-CT-059
Posts : 6
Times Thanked : 1
Join date : 2020-07-10
QTH or Location : Jordanstown
Equipment Used : None, researching it.

Impedance of mic for tti TCB-550 (AMC-5011)? Empty
PostSubject: Re: Impedance of mic for tti TCB-550 (AMC-5011)?   Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeWed Jul 22, 2020 10:09 pm

Thanks Victor, I appreciate the time taken to reply.

Yes, 470R struck me as in the sweet zone, i did wonder if some rigs needed a much lower impedance, hence the question.  I have looked at the inside of the mic and I can see a soldering iron burn on part of the casing, so clearly someones been in there. I checked the magnet with a screwdriver and its field does seem weaker than i would expect;  fear ye not, I'm an electronics engineer. So although the coil and membrane are intact, i think the magnet appears very weak and is delivering a weak voltage output signal. I'll maybe scope it tomorrow and see. 

I have ordered a new mic,... what's the worst that can happen.


Cheers

Keith

Victor likes this post

Back to top Go down
View user profile
Victor
CT Directors
CT Directors
Victor

Call Sign : 26-CT-3228 Ham M7VIC
Posts : 1010
Times Thanked : 63
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

Impedance of mic for tti TCB-550 (AMC-5011)? Empty
PostSubject: Re: Impedance of mic for tti TCB-550 (AMC-5011)?   Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeWed Jul 22, 2020 10:27 pm

No worries Keith,

Was nice to waffle as it can often help someone else out being a public forum and all that.
Always a good thing to pass a little knowledge on.

Well, a fellow tech....you'll appreciate how the heat of a soldering iron and the AC field most hobbyist irons produce can completely screw up a microphone magnet! Wink
Ha! Very Happy Seen that one a few times myself with attempts at 'rewiring' or 'repairing'. Then how else do we learn but for our mistakes....if it's not "Eureka" we herald, it's "Woah! That's weird?"


All the best to you Keith and I hope you get it sorted. I'm sure you will.

Victor
Back to top Go down
View user profile
MadHax
New Member
New Member
MadHax

Call Sign : 68-CT-059
Posts : 6
Times Thanked : 1
Join date : 2020-07-10
QTH or Location : Jordanstown
Equipment Used : None, researching it.

Impedance of mic for tti TCB-550 (AMC-5011)? Empty
PostSubject: Re: Impedance of mic for tti TCB-550 (AMC-5011)?   Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeTue Aug 04, 2020 11:01 pm

Hello Victor, 'twas the mic, bought a new one from ebum, which was the same price as the rig, and wham-bam, i'm modulating; so i'm happy, thanks for the reply.

K

Victor likes this post

Back to top Go down
View user profile
Victor
CT Directors
CT Directors
Victor

Call Sign : 26-CT-3228 Ham M7VIC
Posts : 1010
Times Thanked : 63
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

Impedance of mic for tti TCB-550 (AMC-5011)? Empty
PostSubject: Re: Impedance of mic for tti TCB-550 (AMC-5011)?   Impedance of mic for tti TCB-550 (AMC-5011)? Icon_minitimeWed Aug 05, 2020 5:59 am

Hiya Keith,

Nice one, glad you got it sorted out and thanks for letting us know. As I said, not just for me but for others who may read this on another day and maybe helps them too.


All the best,
Victor
Back to top Go down
View user profile
 
Impedance of mic for tti TCB-550 (AMC-5011)?
Back to top 
Page 1 of 1

Permissions in this forum:You cannot reply to topics in this forum
Charlie Tango 11m DX Radio Group Forum :: Help and Discussion Forums :: Standard Multistandard CB Radio UK/EU/Multinorm-
Jump to: