Ok, so when I run the
Sennheiser frequency finder for my area and I find that, for example,
channel 44 is vacant, I then look up on
wiki (
Television channel frequencies - Wikipedia, the free encyclopedia) and find that
channel 44 corresponds to 3 different frequencies (651.25, 651.31 ,655.75). From this, I assume I can put mics on two of those (since the first two are pretty close together I would only use one of them). Am I doing this correctly?
The frequencies that you found on Wikipedia correspond to the
NTSC Luma (brightness) and Audio carriers of an
NTSC (analog) television signal (and they threw in the ATSC pilot signal just for fun, even though it doesn't occur with
NTSC signals). A television signal is not narrowband around these frequencies, but rather spans an entire 6 MHz
block (analog, not so evenly, but it does fill it).
DTV actually fills this 6 MHz
block equally throughout (which is actually good news for us, because the signal energy is spread out!).
So, if
Channel 44 is vacant for you, I would say you can probably fit upwards of 6 or 7 mics in that 6 MHz
block (ranging from 650 to 656 MHz, spaced ~800 kHz apart) with a
bit of planning and decent mic receivers (i.e., not
Shure PGX stuff).
BTW, before someone jumps in and says that analog TV is gone, it isn't. Low
power, translators, and Class A stations can all continue to broadcast in analog for a few more years.
I'm still confused about the scanning thing. I've gone through all 8 banks, and only one bank had 4 open frequencies total (all except bank #2 returned zero free channels). Does this mean I can only reliably use 4 mics? I've used over 20 mics in here before without issue so I really feel like I'm missing something.
When you scan, you don't want to use the banks. Rather, scan the TV frequencies that you know are
clear. For instance, scan up from 650 to 656 MHz. This will tell you if that
channel is totally
clear. Be sure you do the scanning with your receivers and antennas in their final locations, btw, as this will affect your results.