Problems with Microphone. Need help!

RevolutionXLR · Post by **RevolutionXLR** » Mon Mar 19, 2007 4:49 am

Hello!

I'm using some brand new Motorola GM380 mobile radios (UHF & VHF) for HAM-radio. TX and RX performance are great. I love them! But I have some trouble with my microphone modulation: The volume is OK but it seems that the microphone or the radios have some build in high-pass filters. So in some cases I get reports froms other stations, that they can hardly hear me because their speakers are not able give out my high-frequent modulation. How can I expand my dynamic range??? From Moto to Moto modulation is fine but some radios from yeasu and icom can not handle it.
There is no option for modulation in the CPS exept the mic gain but mic gain is set to an accurate level.

How can I kill that high pass filtering through the microphone?
I'm using a MDRMN40258 enhanced microphone. I also tested a GMN616A but this was even worse.

I haven't opened the microphone yet. Does anybody now about a build in high-pass filter and how to bypass it?

Thanks a lot for any hints!!!

RevolutionXLR · Post by **RevolutionXLR** » Mon Mar 19, 2007 7:27 am

I just opend the Microphone a took a picture. Any ideas?

HLA · Post by **HLA** » Mon Mar 19, 2007 7:39 am

your problem probablly isn't in the mic, read the radio and see if somebody turned on the audio processing filter or the compression/expansion or the companding feature. any of theese could be causing your problem and if they are not turned enabled on all of the radios you will get the sounds you are describing.

phrawg · Post by **phrawg** » Mon Mar 19, 2007 7:50 am

also ckeck that on the ham programmed channels
you are not set for narrow band. Phrawg

RevolutionXLR · Post by **RevolutionXLR** » Mon Mar 19, 2007 8:07 am

I just read the radio:

"Voice Pre-Emphasis/De-Emphasis" an "Low Level Expansion" are turned on. All other stuff like XPAND are off.

I use this options also on my GP380 portable radios but in contrast to my GM380 they work great with perfect dynamic sound although the GP mics are tiny.

RevolutionXLR · Post by **RevolutionXLR** » Mon Mar 19, 2007 10:14 am

Thanks! I got it!

After deactivating "Voice Pre-Emphasis/De-Emphasis" the dynamic range of the microphone is OK now.

Unfortunately the Pre-Emphasis is forced with the De-Emphasis option and so I now have a terrible signaloutput through my speaker. Now just the other way around.

Thanks for your help!