> I'll take most of what you said as being sarcastic, but your point
is taken.
I guess so, just pointing out the apparent absurdity.
>If so, great, you're done. If not, fix it.
In the end though, the function of the pass adjustments is simply to
transfer energy at the pass frequency with minimum loss.
IF everything were really 50 ohms resistive, then we could tune in
the lab, and we could mix and match cables and equipment without any
concern or adjustment. Unfortunately, as someone pointed out a ways
back, real equipment is rarely so idealized. The measures
for "fixing" it may induce more loss than what we are getting with
the non-ideal system.
On the transmit side, power is cheap and a little extra loss
(fractional dB) isn't an issue, so I think the idea of tuning the
pass pretty close with whatever you have is probably workable. Either
an SA and tracking generator, or HT and bird, simply adjusting the TX
pass for maximum power out.
On the receive side, the power isn't free, it can be considered very
expensive, and we would like to save as much as we can, especially if
it's only cost is an adjustment. But we don't have such a problem
here, this can be adjusted with the real cables and receiver
attached, so you are tuning the system, not just the cans themselves.
The notches are no problem to tune at full power, so not an issue
either way.
> With the cavities tuned to resonance, cable lengths are no longer
an issue.
> Needing to use "magic" cable lengths should be a red flag that
you've got a
> Z mismatch somewhere.
Well, in the real world, we always do, to some degree.
The method that I'm using at the repeater now, is to tune the pass at
low power using an HT as signal source. At 5W, I can't believe that
we are anywhere near the damage threshold. I can also tune it using
the SA and generator, slightly different point, but after a lot of
back-and-forthing, I found that the HT method gave me slightly more
output when connected to the real transmitter than the SA method.
Still, we're talking small percentages of difference.
Receive pass, and notches are tuned while injecting a signal using a -
50dB tap between the antenna and the bandsplitter. This is similar to
the "broken tee" method, except that I am using a calibrated tap that
is flat well beyond 2M and 440. I am getting good numbers (-126 ish
dBm) for copyable signal, and the notches and receive pass align very
closely to where they do when tuning with the SA and generator, but
not exactly the same place. (as expected)
I go up today to replace the water-damaged GP-9 which is apparently
more and more a dummy load as time goes on, and to supress some nasty
feedback that's happening whenever the UHF system is active.
I'm very tempted to build a calibrated signal source, it would be a
lot more portable than my HP generator. But I am not sure it's really
worth the effort.
> Even the demigods that hail from Waco, Marlboro, and Angola aren't
> infallible, especially after the evil Brownshirt Brigade
percussively
> retunes their products while en route to you. All Hail Maxwell!
All Hail
> Maxwell!
Indeed! I once got an HP SA shipped to me in foam-in-place packing,
where the brown guys managed to bang it hard enough to snap off one
of the cast aluminum handles! We returned it without powering up.
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