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Transmitter combining.



Transmitter Combiner experts:

We chose two adjacent channels for our two satellite UHF downlinks
thinking that it was the most economical use of the satellite spectrum
since any single user will see the same doppler on both and so we do not
need to waste bandwidth with a 25 KHz guardband in between them.

The two frequencies are separated by 25 KHz.  What is the the consequence
of the intermods for such a narrow separation.  Obviously there will be a
very strong 25 KHz component, but Is that any worse than a 1 MHz
component?

The transmitters each feed a 90 degree hybrid and two 90 degree whips.
There should be about 20 dB isolation?

THe only first order significance we can think of is that the tank
circuits of each transmitter will offer no additional off frequency
attenuation because of their nearness, but at 435 MHz, we doubt that a
1Mhz separation will have that much either..

ANyone do this for a living and can comment on the desired transmitter
separation?

Bob



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