I have an Azden 310LT system in the 566.125--589.875 range. If I wish to add another and use at the same time, can I get the same "UHF range" and simply select different frequency? These systems provide 188 UHF selectable frequencies.

Yes you can. I've used the Azden 500U some years ago with up to 6 units running to a board and as long as there is seperation of frequencies and nothing else in the area of the freqs you're using you'll be OK. Obviously it would be best if all the ranges/freqs were as far apart as possible but in practical terms that isn't always feasible.

Thanks Don, I will shoot for freq's at the top and bottom of the range.

"I will shoot for freq's at the top and bottom of the range"
- That's really not the best way to select frequencies. I don't know about your Azden system, but most frequency agile system receivers have some kind of scan function for finding an 'open' frequency. RTFM.

They may have 188 frequencies, but *not* 188 usable frequencies!

You need to talk to the manufacturer and get a list of intermodulation-free frequencies that you can use together at the same time and only use those frequencies.

Scanning may help - but you *must* choose a frequency that will not cause any interference to the others you are using.