Hello John,
> "W3ML" <w...@...> wrote:
> Hi,
not since high school... :-)
> I have now read two different things about where to put
> the pre-amp.
Only two?
> One says before the Bandpass and one after.
> What I have now is the 6 can duplexer is hooked to the
> bandpass and then on the other side the pre-amp is
> connected and then a cable goes from preamp to radio.
> The other article I read this past week says the preamp
> should go between the cans and the bandpass.
> Which is right? Or does it matter?
Depends and it does matter... based on how busy your radio
site is, where any other rf activity is relative to your
frequency, the type of preamplifier, how it's constructed,
your receiver front end, your duplexer type with number of
cavities, your Tx Power level and a few other tidbits...
got a headache yet?
I'd venture to say... if your receiver front end is
of decent Q (quality) and reasonably narrow band-width
along with a decent duplexer... then the preamp might
best go after the duplexer, between it and the band-pass
cavity.
If your receiver front end is average or fairly broad (a
few MHz band-width) there might be a case to include the
extra band pass cavity after the preamp before the
receiver input. Some of this option depends on the duplexer
and TX Power Level.
The point of what I write above is about trying to obtain
the best overload prevention performance and or damage
control when the preamplifier is overloaded and generating
unwanted signals.
Many but not all the variables are are in the list.
You could of course try both positions and measure the
system performance.
s.
