It sounds like you are on the right track! Keep going!!
A few years ago I had a local ham tell me my UHF repeater was producing a spur
on his UHF output. He made a fuss that I was not running good gear, or
adequite filtering. I assured him that I was fine & had checked it out with
my equipment. He offered to come to my repeater site with a spectrum analyzer
& mentioned several times that since he was an engineer (working for Fujitsu)
he would like to trouble shoot the problem at my location & would help repair.
I declined his request. (Apparently he did not realize that I also am an
engineer working in FM broadcast) He then requested I turn off my repeater, &
I refused. He then found out that my repeater transmitter was a GE Mastr Pro
& suggested I upgrade to a solid state transmitter, claiming that an old tube
PA was likely the cause of the problem!!!! (I refused) He then made a fuss
with the repeater coordination coucil, of which we were BOTH board members.
Eventually, it came down to a local ham (WA7ABU) member of the coordination
board inspecting BOTH our repeater sites. The inspector found a mix that was
occuring in HIS (the complaining party's) location!! (Which was a solid state
PA deck!!)
Obviously, this has noting to do with the subject but is a fun story.
------ Original Message ------
Received: Fri, 01 Jul 2005 06:54:32 AM CDT
From: Paul Kelley <[EMAIL PROTECTED]>
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results)
> I just spent another night poking around in this thing.
>
> Sniffing around the transmitter with a receiver and very
> small probe "antenna" I am reasonably certain the spur is
> present at Q305 (exciter mixer) and all subsequent stages.
>
> Using a general coverage receiver the fundamental output of
> the channel element (19.195833 MHz) seems free of spurs. I
> realize the third harmonic of the channel element is
> selected by the filter but I have no receiver covering that
> range.
>
> Similarly, the 16.7 MHz out of the offset oscillator seems
> OK. There are some very weak (more than -100 dB) spurs
> above 16.7 but it is absolutely quiet at 15.790 which is
> what would be required to cause my +910 kHz spur.
>
> So I suspect a problem in either the exciter mixer (Q305) or
> somewhere in the injection multipliers (Q101, 102, 103) on
> the receiver RF & IF board). No amount of tuning or
> detuning these stages eliminates it.
>
> It still seems odd that I have two Micors with an identical
> spur problem.
>
> Any thoughts on what to try next?
>
> Paul N1BUG
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
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