> -----Original Message-----
> From: Thomas Oliver [mailto:[EMAIL PROTECTED]
> I like to tune the duplexer with service monitor for best peak and notch
> like you did then hook up repeater and check reflected power at
> transmitter
> output as you did and compare foreward and reflected readings with
> duplexer
> inline and out of line.
I compared the two as well even after the cable *fix*. I don't know if I
would rely on that method though. It seemed to be higher swr when I checked
it between the TX and the duplexer. I think it's one of those cable weird
nesses.
I like the idea of reading the loss through it.
>If reflected power is more with duplexer inline
> then most likely there is an impedance mismatch between the duplexer input
> and the transmitter output. If the difference in reflected power is small
> with duplexer in/out, I just tweak the first pass adjustment (tx off) for
> minimum reflected and usually can get a good match equal to reading with
> duplexer out of line.
When you do this, do you go back and adjust the notch?
>If the difference is great like you described then i
> try a different jumper a little shorter or longer.
That is something I would not have thought of if not for this list and
repeater-builder.com. Ain't the internet neat.
>Wacom had a procedure
> for finding the right length jumper it was to add right angle conectors or
> jumpers increasing in length an inch at a time (two inches at a time on
> two
> meters) until you have added 1/2 wave total and the lowest reflected
> reading was obtained then make a new jumper with the new optimized
> length.
Nice technique. I got lucky and had a cable already made up that was just a
few inches longer.
> You could have had a bad cable or it may just cut to a length that made
> the
> transmitter mad.
I think it was the length. Will never know as I don't plan on putting that
cable back in service!
>
> If your tx output and duplexer input were 50 ohms then any length 50 ohm
> cable would work. But in the real world if your service monitor is not
> exactly 50 ohm and transmitter output and duplexer input is not exactly
> 50 ohm Changing length of the jumper will
> improve preformance as you described because your jumper is acting like a
> transformer.
Weird stuff. Trial and error seems to work best.
Thanks for the input!
-Tim
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