--- Mathew Quaife <[EMAIL PROTECTED]> wrote:
> Well the figures I took are from memory, but your
> right, it's more likely about 80 watts out, but at
> either rate, got the answer that I was looking for.
> I'm not changing anything here, as it works, and if
> I mess with it, it WON'T, but one of the students
> hit me with this question, and I was stunned, so
> needed the answer. Besides, if I took out two of
> them it would look odd, and I would never sleep
> right, they fill the bottom of the rack just fine.
> Thanks.
>
> Mathew
>
Now that we have the real question you can get a beter
answer. Again assuming 2 meters with a 600 khz split
teh reason for 6 cavities is to keep the transmitter
noise out of the receiver. A transmitter will not
only put out a signal at the desired frequency but a
broad band of frequencies. Around 600 khz it may be
60 to 80 db down from the carrier. If the receiver
will hear a signal of -120 db the duplexer has to make
up the differance of 40 to 60 db if one watt is used.
If 100 watts is used then you need 20 db more or 60 to
80 db of rejection. Two cavities will give the bare
minimum in most cases if good solid state systems are
used. The third cavity is added then you get a safety
factor just incase . Most of the time even with
proper tuning the transmitter and receiver will not
have enough selectivity without the third cavity.
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