Hi Doug,
> "Doug Zastrow" <[EMAIL PROTECTED]> wrote:
> Skipp,
> I want to make sure I've got this straight in my head...
> For the final tweak on the transmit side bandpass setting I would:
>
> A) Look for minimum reflected power from the duplexer 'xmt'
> port back to towards the transmitter.
Yes, if the duplexer antenna port is a proper/true 50
ohm load. I use a termination/load for that adjustment.
> B) And then I'd also look for maximum forward out of
> the duplexer 'ant' port towards the antenna.
No, you'd like to see that... but it won't happen with
min swr (reflected power).
Sometimes min reflected power and max output power are
near the same adjustment location. One doesn't often see
min ref pwr and max fwd power coincide.
Unless you've checked with some high end test gear, you
don't know what the transmit signal spectral purity is
in detail. All the forward power might not be the best
signal going out the pipe.
Keep in mind the band pass cavity is also a tx signal
filter... Crappy transmitters will be cleaned up a
bit (sort of). Some of the lost forward tx power might
be mucho undesired energy.
Also keep in mind the minor changes in the rf amplifier
performance with true vs reactive loads. The effect is
much greater when you don't use a circulator.
> I suppose the wattmeters could cause some interaction
> that would change things when removed....
> Am I close?
> Doug
There will always be some interaction or reactance with
every bit of added hardware. But using true 50 ohm loads,
quality meters and coax cables helps to reduce serious
system impedance bumps.
cheers,
skipp
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