Recently I had problems with interference on one of my U87
ai microphones. After some investigation, this turned out to be caused by a time code transmitter (432 MHz, 10 mW) in the vicinity of the microphone. Because it was unclear whether the interference signal came in via the cable or through the openings in the headbasket, I initially tried to solder additional capacitors directly to the pins of the XLR insert, unfortunately without noticeable results. Surprisingly, an older U87
i does not show any sensitivity to HF fields in the immediate vicinity.
Would there be a solution to make the U87ai more resistant to (fairly low) HF fields?
I want to try wrapping the microphone in aluminum foil to see if additional shielding will solve the problem.
(Although that is of course not a workable situation!
)
EDIT: If I wrap the headbasket with aluminum foil, the interference disappears completely. It therefore appears that high-frequency signals enter through the mesh of the headbasket.