[UK-CONTEST] Adjacent Channel Interference

[Ray Hills]

I was interested to read about the potential interference between DVT and 
mobile.  For a long time the use of channel 21 for analogue TV was avoided 
because of the potential for interference to PMR users just below the band 
edge.  In the end the use of CH21 became unavoidable and Marconi produced 
some very special "brick wall" filters for use at the CH21 stations.  As I 
recall they had at least three resonators in the signal path which, together 
with the four-channel combiners called for some pretty sophisticated 
impedance matching as well as the need to handle many kilowatts of power. I 
don't remember the numbers but the pass band cut off very sharply below the 
TV allocation.  Maybe the same solution will apply?.

Ray G3HRH