R
rbrucecarter5
Guest
I just heard a new commercial for HD radio - a car dealer offering a free HD radio with a car, then going on to say an HD radio can get "over 600 channels" free. WHERE in the name of sanity did they come up with the "600 channel" number?
OK:
AM HD jams 1st and second adjacents. 50 kHz bandwidth required. 1.16 MHz of spectrum divided by 50 kHz = 23.2 So - 23 HD AM stations assuming optimum band packing.
FM jams first adjacents. 600 kHz bandwidth required. 20 MHz of spectrum divided by 600 kHz = 33.3 So - 33 HD FM stations assuming optimum band packing. If they all run HD-2 and HD-3 then you have 100 "channels".
AM plus FM absolute maximum is therefore 123 channels per market.
In order to get 300 channels, you would have to assume every frequency is utilized on FM, all of them are HD, and all use HD-2 and HD-3. That would make 300 channels. Of course it wouldn't work because first adjacents are jammed.
OK:
AM HD jams 1st and second adjacents. 50 kHz bandwidth required. 1.16 MHz of spectrum divided by 50 kHz = 23.2 So - 23 HD AM stations assuming optimum band packing.
FM jams first adjacents. 600 kHz bandwidth required. 20 MHz of spectrum divided by 600 kHz = 33.3 So - 33 HD FM stations assuming optimum band packing. If they all run HD-2 and HD-3 then you have 100 "channels".
AM plus FM absolute maximum is therefore 123 channels per market.
In order to get 300 channels, you would have to assume every frequency is utilized on FM, all of them are HD, and all use HD-2 and HD-3. That would make 300 channels. Of course it wouldn't work because first adjacents are jammed.