Paul,
A spur is ususally produced by multiplier circuitry in the transmitter. I would retune the exciter and pay special attention to the position of the slugs prior to retuning. Second you might just have a defective exciter board. Most exciters filter the multiplication stages so that spurious responses and conversion gain loss are minimised if you an get another exciter you can compare the two!
neil Ve2boa-----Original Message-----
From: Repeater-Builder@yahoogroups.com
[mailto:Repeater-Builder@yahoogroups.com]On Behalf Of Paul Kelley
Sent: Thursday, June 30, 2005 3:07 PM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] UHF Micor (mobile) spur
Aarggh! I've pulled out most of my hair on this one! To
revisit something I asked about several months ago... I'm
still having a problem with my UHF Micor mobile converted
to repeater.
It is a T34RTA3000AA with power set at 20 watts. It is on
444.000 (T), 449.000 (R) and is producing a spur at
444.910. The spur is "clean", stable, and has good
modulation, sounds identical to the main carrier.
I have retuned the exciter filter per the book several
times. No change. I swapped the KXN1024A channel element
for one on a different frequency (443.750T/448.750R) and
still had a spur 910 kHz above my carrier freq. Finally I
tested both channel elements in a stock (unmodified) Micor
and STILL have a spur 910 kHz above the carrier frequency!
I lack equipment to accurately measure the spur power level,
but this spur is some 80 or so dB below the carrier level,
perhaps a bit more. The manual specifies spurious and
harmonics below 85 dB so this MAY be within spec. but why
would it always spur 910 kHz above carrier freq.????? This
is an unacceptable level as it can be heard up to 5 miles
from the repeater on line of sight paths (and this is
causing a problem for some people).
What am I missing? Is this normal behavior for a UHF Micor?
I have juggled some numbers around and can't see why this
would always be 910 kHz above the carrier freq. Thought I
had a bad Micor until I found identical results in the
second one...
Any ideas? Should I forget about asking why and just throw
cavities on the thing until I knock the spur down enough?
Paul N1BUG
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