Maestro Transmit Audio Distortion

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  • Updated 1 year ago
Recently acquired a Maestro to enhance the potential of my well-liked Flex 6500.  
During the recent CQWW, I got numerous reports of scratchy audio.  This was the first
use of the Maestro.  Using the 6500 without the Maestro produces transmit audio of enviable quality, but with the Maestro sounds reminiscent of RF feedback are very noticable.  

I have not yet located a similar problem in the archives.  

I find that power level of 1 watt produces the same effect as a KW.  The microphone is the same, as well as virtually everything but the Maestro.  Microphone levels, processor levels, etc. have been experimented with but no help.  The well matched antenna is 200 feet away, and the system is well grounded.  On air tests as well as using the monitor feature of the rig confirm the reports of scratchy sounding transmit audio from the Maestro.    Running the latest windows software 1.9.13.  The problem disappears when using the 6500 without the Maestro.   Suggestions?
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Posted 1 year ago

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Tim - W4TME, Customer Experience Manager

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It would help if you described the mic you are using and how it is interfaced to the Maestro.
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Mike Smoot

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Just a thought - IF you are using a magnetic or other non-powered mic element during your tests, make sure the mic bias is disabled at the the Maestro as well as at the Flex.
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Ria - N2RJ, Elmer

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Last night I was on with a group (G0EVY and friends on 75m) and someone in the group was having a problem with his audio where it would sound like someone with excessive vocal fry. He was using a 6500 with maestro with the included mic connected to the maestro. I stumbled upon this and was wondering if it could be the same issue with the Bias.

Is there any guide that shows recommended mic settings to use with the included hand mic? 
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Tim - W4TME, Customer Experience Manager

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Ria - the issue you reported can be a variety of things.  If he is using the FHM-1 hand mic, it uses a dynamic element, which has low output gain.  Because of this, you have to use the +20 dB mic boost and close talk across the mic.  If you have the mic gain set too high or the high end of the EQ boosted too high, you can get distorted audio that may sound like frying.  There is a section in the FLEX-6000 Hardware Reference Manual regarding how best to set up and use the FHM-1 and a HelpDesk article (  

The other thing that comes to mind is a possible RFI issue.  By running the Maestro off of a battery and connecting it via wifi, you eliminate the main ingress points for RFI, but this does not exclude the mic cable, which if the ground is broken, can cause the cable to act as an antenna allowing RFI to get into the codec on the Maestro.

The first troubleshooting step I'd recommend is to see if there is a change if the mic is connected to the radio rather than the Maestro.

The default mic profile for the FHM-1 is a good starting point, but everyone's voice characteristics are different and to set the EQ, you really need to listen to yourself in a 2nd receiver so you can hear what you sound like over the air.  I highly recommend this HelpDesk article for anyone operating phone (

And one other thing.  On the Maestro MIC-1 connector, the bias voltage is always enabled on the MIC+ line.  The BIAS switching on the MAestro is only applicable on MIC-2