Maestro Mic 1 Noise

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  • Updated 1 year ago
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I am using a Maestro with my 6700. When I use the 6700 for the mic input, which is most of the time, the quality is good with very little background noise. And the DEXP feature makes it better.

I got a FHM-2 with RJ-45 for the Maestro, to use with a battery and be away from the radio and use it. Works OK, but I find the level of background noise is high when using the FHM-2 connected to the Maestro. And there is no DEXP support in this configuration. The noise seems to be generated in the Maestro, you can turn up or down the mic gain and it does not change. You can hear the noise in the monitor, and see it on the TX level meter.

Do others have this issue when using a mic input on the Maestro? Or am I missing something.

/Doug
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Doug - W3UB

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Posted 1 year ago

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Larry - W8LLL

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I have been seeing the same thing with the exact setup you speak of, also I find it strange that turning the mic gain to zero will still produce up to -10 db signal on the level meter when speaking. I have monitored it with other radios in the shack with no antennas connected to them and the maestro set at 1 watt on ssb and it is showing power output on the other radio without saying anything.


I just plugged in one of my Heil PR-781's into maestro mic2 and it has eliminated this issue that I get with the FHM-2.

(Edited)
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EA4GLI - 8P9EH - Salvador

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I have seen the same behavior in my maestro.
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Doug - W3UB

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Yes, it seems like a Maestro HW issue, somehow noise (seems digital in nature) is coupling in to that input. Will have to try Mic 2 and see how that works.
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Larry - W8LLL

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Unplug the FHM-2 mic head while in mic 1 connector and the noise goes away.
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Ronald / W4RJF

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I believe I experienced this same issue with my Maestro and the FHM-2...I finally replaced the RJ-45 connector on my FHM-2 and it solved my issue...hope this helps...

Ronald
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Ken - NM9P, Elmer

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You can use CAT5 or CAT6 as a makeshift mic cord.....BUT..... you will not have good shielding of the Mic audio if the lines used for Mic- and Mic+ are not part of the same twisted pair inside the CAT5/6 cable.  There are two different common wiring standards, and they use different arrangements of the pin-outs.

The most common/standard CAT Cable uses twisted pairs for pins 1-2, 3-6, 4-5, and 7-8.  The difference is the particular color pairs they use for each pin combination.

The most common standard in the US, at least is this:RJ45-Pinout-T568B
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Ken - NM9P, Elmer

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Oops...Tim has already posted a great description here:

https://helpdesk.flexradio.com/hc/en-us/articles/206971923-Identifying-the-Wires-Connected-to-a-RJ-4...

NOTE that the Mic- and Mix+ of the Flex RJ-45 are assigned to pins 4 & 5 respectively.  So the mic SHOULD have good isolation if you are using a properly wired CAT 5/6 cable.  Unless there is a wire-bridge between two pins on one end of the connector.

HOWEVER:  there have been reports that some inexpensive CAT 5/6 cables and patch cables have been found to be wired incorrectly.  They will pass a one-to-one continuity test, but they are not using the correct pairs on the correct pins.  (For high speed internet, they will "work" but can have crossover interference resulting in slow-downs and lost packets.

I have begun making my own patch cables and changing them all over the house, so I can know that they are correctly wired.
.  
You might examine your cable as well.
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K1UO - Larry

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That color code does not seem "standard" as I was taught by Bell Labs that Blue, Orange, Green, Brown, Slate was the sequential base for cable color codes. Of course it can be anything to the Company wiring up the mic element and RJ45 connector I suppose :)
(Edited)
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David Decoons wo2x, Elmer

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Larry, you are correct for 66 block punchdowns in the telco world but for Ethernet networking the above diagram is indeed TIA/EIA 568B standard.
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K1UO - Larry

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Thanks Dave...  takes me a bit of getting used to :)
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Tim - W4TME, Customer Experience Manager

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I have entered this problem report into our bug tracker as issue #5024
for additional investigation. Thank you for the defect report.
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Doug - W3UB

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All very interesting.

I tried a Yaesu MH-31 head (RJ-45) and my MD-100 head which has an RJ-45 input, both using the FHM-2 cable, and both worked fine with no noise. The mic levels are low and require high mic gain, but work fine (except the up/down buttons). Perhaps the issue is inside the FHM-2? Will ponder that later.
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K1UO - Larry

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Sounds like the FHM-2 mic element is hot all the time and not switched through the mic ptt. 
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Ken - NM9P, Elmer

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Yes, otherwise VOX wouldn't work. The old standard of shorting the mic leads when receiving was from back in the AM CB days when the audio amp did double duty as receive amp and tx modulator.
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Doug - W3UB

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Finally had time to look at this.

The issue, as I see it, is noise coming from the Maestro on the +5V mic bias line. It is fed into the FHM-2 element via a 2k resistor. I bypassed the +5V input with a 100 uF cap (the only one I had) against mic ground. There is room to place the cap inside the mic underneath, where there is another cap in series with the mic output.

Eliminated most of the noise, and is now usable. The cap size should be a bit larger. Or the noise should be handled inside the Maestro.

/Doug
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Andrew Russell

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I have also seen this with Yaesu/Vertex electret microphones.
Andrew de VK5CV
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Doug - W3UB

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Should have added, if the resistors were not 0402 it might be better to build out the resistance in the +5V bias line, to give any added capacitance something to work against.
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Tim - W4TME, Customer Experience Manager

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Doug,

Thanks for the additional feedback.  We have this issue scheduled to be investigated for the next release after 2.0.  This information is greatly appreciated.