> You can't simply cut the jumper cables to a certain fraction of the
wavelength, because the coupling loops inside the cans are part of
the total length.
That's what I figured.
It takes a network analyzer to determine the optimum length, and
> most folks simply don't feel that it's necessary to go to that
extreme.
Have SA and tracking generator, but not network analyzer.
Could I emulate this by tuning with an HT as a signal source, and
looking for minimum reflection? I have 500mW bird slugs.
I know people say that you can't tune them with power applied, but
there has to be a damage threshold, otherwise you couldn't tune them
at all!
> He uses a network analyzer to measure the insertion loss between
two cans at a time, and then he will try a longer or a shorter jumper
until he finds the optimum.
I'm trying to picture the setup here, and where he's measuring.
When I am doing the pass frequency, I have the SA at the antenna
terminal, and the tracking generator at the other end of the
appropriate can pair, with the unused one terminated.
> Needless to say, he soon has a list of "sweet" lengths to start
with for each frequency, so it normally takes only a few tries to get
it on the nose. It is still a "cut and try" approach, but it works.
Hmm. Assuming that my measurements show that we aren't getting what
we should, I guess I could make a guess in the appropriate direction,
and see what happens. The nice thing about doing the UHF connectors
with FSJ1-50 is that they are easy to take off again. I have plenty
of cable, so I'm not worried about expending that, and the connectors
are silver/teflon.
> The typical spectrum analyzer works in transmission mode, and
doesn't have
> the extreme reflection sensitivity needed to properly tune for
bandpass. A
> good spectrum analyzer with a return-loss bridge can probably be
used in
> place of a network analyzer for this task.
Hmm. I know what you mean here. I did return loss measurements on
telco equipment with a bridge that I built, but I'd be nervous making
one up for VHF work.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
