It appears as though the entire frequency range that your units are in are clear of TV broadcast in your area. This does not mean that there are not other unlicensed users in your area interfering.
I second, third, fourth (whatever we are up to here) the idea of getting you receivers closer to you transmitters.
Let us know how that effects your problem.
Also, Is this a new problem or has it happened the entire time you've had these systems?
Is it a problem on each combination, no matter which transmitter and which receiver you use in combination with the other or does it track with a single receiver or a single transmitter?
Are you using other wireless system in the same space or elsewhere on campus?
Have you frequency co-ordinated them all to work together?
If not, it's quite possible that you are causing yourself your own interference. You can't just change one frequency set on one mic if all systems are in the same frequency range. A single change can often mean that 3 or more tx rx systems will now have problems.
Let us know your entire wireless layout in terms of number of systems, what frequency range and what frequencies that you currently have them set to, this will help to diagnose your problem.
His,
Lee Buckalew
Pro Sound Advice, Inc.
