Can't Find Unused Mic Frequency

[RMSdrama]

Hi folks,
I have 2 GTD Audio G-787 wireless mic systems, and it's worked okay for us in the past. It worked great in the fall, actually, but now we can't seem to find any open frequencies for one of our mics. The receivers have group numbers, and this one operates from groups 9 to 12. In the master frequency list, it's 570 to 579 mhz. Everything is full, and the mic cuts out or gets scratchy. I've tested all equipment and spent hours trying to find frequencies and researching stuff online. If anyone has any insight as to why this suddenly doesn't work or how to find an open frequency, I would be very grateful. Like I said, it was fine 5 months ago, and now it's suddenly full, making a mic unusable. Any suggestions?
Thanks!!

[zenguitar]

Help us to help you.

Don't assume, tell us where in the world you are. It really does make a difference when it comes to wireless frequencies.

Andy

[Hugh Robjohns]

If you're in the UK, 570-579MHz span channels 33/34. These are designated for short-rerm (ie, for specific events) PMSE use, and must be licensed for specific locations and dates.

[RichardT]

Fall = US or Canada!

[resistorman]

Frequencies are full because someone or something is using them, or something nearby is generating interference. It would seem some new device(s) have come online in your area. It seems to me there was a thread about RF spectrum analyzers not long ago, but I can't find it.