[Scott Dorsey]

wrote:
I have been having trouble with interference on Shure UHF microphones.
I typically use bewtween 8 and 15 in the same room. I've tried
antenna distributions with limited success. I've been advised to put
all the wireless on the same group, but I find that advise to be
suspect. The groups the mics have are a1, a2, 1,2,3,4,5,6,7. I think
the problem might be with the pda's and cell phones that clients
bring. If anyone has any advise or insight, it would be greatly
appreciated.

You have two issues: outside interference from other sources, and
inside interference from the various transmitter products mixing together.
You need to find channel assignments free of both.

GSM cellphones will cause interference issues with those wideband
receivers, and there's nothing much you can do about it, other than
to keep the receiver away from the cell users and use preselectors
or better receivers.

For the issues with the individual transmitters interfering with one another,
the Sennheiser website has a gadget where you can plug in your wireless
frequencies and figure out where the intercepts fall. You need to do
this in order to lay out a reasonable signal plan if you're going to be
using that many units together. In addition, you may want to do a sweep
with a spectrum analyzer or at least a cheap scanner and make sure all
the spaces are clear.

When you do the intercept math, get a list of a few more channels than
you will actually need, so you can relocate some units to deal with
outside interference.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."