Great post! Lots of info in one place.Generally a combination of lack of RF filtering on pin 2 and 3, and improper connection of pin 1 go case.
See a copy of "Radio Frequency Susceptibility of Capacitor Microphones" from the web site of one of the presentation authors:
You can sometimes correct the problem by rewiring the pin 1 connection point, or use Neutrik RFI XLR connectors on the cable.
We leaned on this info heavily while troubleshooting the issue over the previous couple of months and it did improve things. Unfortunately in this location the signals are so strong that even though these measures improve the noise, it’s still around 10dB above the noise floor (depending on the microphone). Fine when using one mic but not fine when recording a large group of musicians as the noise is accumulative.
and that’s with the antennas pointing at the studios turned off!
I’m not sure if I mentioned it earlier but the studio is 200 feet from the antennas