How can I reduce interference with two radio microphones?

Question

(Hopefully not off-topic noob question)
We have a hearing loop set up which uses a Sennheiser collar radio mic and receiver which works pretty well. We recently bought a handheld Sennheiser mic for use in meetings so that hearing loop users can hear speech from audience members. Unfortunately, when both mics are switched on, there is a lot of mid-high frequency interference which makes the system barely useable.

Is there any way to salvage this setup? I've tried various different frequencies and all sound pretty much the same. Do we need a receiver that runs on separate frequencies for each mic?

Answer 1

Generally, for best sound quality you want every mic to be paired with a receiver, and each pair to be on a different frequency. These can then be patched into a mixer.

This not only reduces the likelihood of interference, but also lets you adjust the gain on each mic channel independently - which could be useful in situations such as the one you are describing.