Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Timothy Fidler

Polarity it critical.

There is a small Linear IC equiv approx to  a u741 built into the mic insert.   Generally one of the mic solder tabs on the back will  be marked with a posittive to show correct polarity. Your mileage may vary.

If the mic insert has been reverse powered it may be toasted (there are ways to test this depending on what test gear you have) .  It may well depend on the manufacturer. Some may install a protection diode, some not.

If you wired it  exactly the same way as the previous insert assuming the back solder tabs looked the same you should be fine - they are generally build to the same pattern.  Unless you have photos of what you did originally Red to which terminal etc,  it is surprising how tricky memory can be. 


Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 CB #2885, 
Telephone Whangarei   022  691 8405
e: Engstr@...

----- Original Message -----


Fri, 28 Dec 2018 01:16:00 -0800
Re: [BITX20] Bitx40 - Not Transmitting #bitx40help #bitx40

Thank you , Timothy

I am not using a Dynamic mike, I am using the small electret mike as was supplied with the kit.
I make up the mic with a plastic enclosure and a switch for the PTT.
4 wires, 2 for the PTT and 2 for the Mic.

Just a thought - how important is polarity on the mic ? (could it be that I have switched the Pos and Neg ??)

Have been running the rig on a 13.8 DCV regulated power supply with a 2amp fuse.

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