Nate,
I'd start by doing some "office DF'ing" before spending time on the hill
this time of year. My first guess would be local oscillator leakage from
something on the hill. Try doing an FCC ULS database search for anything
within a mile or so of the site, make a list of the Rx frequencies in a
spreadsheet, and make colums for the "usual suspect" IF offsets (+10.7,
-10.7, 11.2 for M2's, 11.7 for Micors, etc.) and see if you find anything on
147.825 +/- 10 kHz or thereabouts).
A local two-way shop here got a visit from the FCC because of excessive LO
leakage. They were using Mitreks in a repeater installation, and the LO
leakage was strong enough to bother another receiver several miles away.
The FCC wasn't happy with them for using mobile radios in station
operation...
Probably 15 years or so ago I had a dead carrier holding open one of my UHF
ham repeaters (it ran carrier squelch back then). The repeater is 443.800+,
input 448.800. The carrier was there for an hour or more, so I figured I'd
take a drive up to the site (it was about 1AM, but hey, I was bored, and the
site was only 10 minutes away). I couldn't hear the carrier on the input on
my drive to the site until I pulled in the gate, then it started getting
stronger and stronger as I got closer. Then I saw a Motorola service van
parked next to the shelter with the lights on, engine running, and a girl in
the passenger seat. I walked into the site, scaring the bejesus out of the
tech, to ask him what he was doing. He was working on an 800 MHz Ardis box.
I nosed around a bit, trying to find this dead carrier with an HT. Then all
of a sudden it went away, and a few seconds later, the girl that had been
sitting in the Motorola van came into the site. Long story short, the girl
in the van was the tech's girlfriend. He got the service call, and she
decided to come along for the ride to keep him company. While he was
working, she turned on the radio in the van and was listening to 101.5FM.
The LO in the FM radio, like many FM radios, is 10.7 MHz high-side, so
that's 112.2. The fourth harmonic would be, you guessed it, 448.8. And the
mystery was solved.
--- Jeff
> -----Original Message-----
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] On Behalf Of Nate Duehr
> Sent: Thursday, January 12, 2006 7:19 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] OT - NOW NOT SO funny
> interference story
>
>
> We're also hunting a "dead carrier" on the repeater input of
> our 147.225
> system in Denver. Total pain in the ***.
>
> The only antenna that appears to hear it reliably is the one
> that's up
> on the tower, on the mountain... of course. Nothing at
> ground level has
> been able to pick it up yet, and it's too cold/windy to
> really be up the
> tower with a receiver and yagi this time of year.
>
> The carrier/mix is not toned, of course, and the repeater is
> -- so the
> system is still "usable" but boy does it sound bad when weak-signal
> users use the system.
>
> Sigh...
>
> Nate WY0X
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
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