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.
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.
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.
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.