At 5/25/2006 08:01 AM, you wrote:
>Has anyone experience with eliminating noise fom the metalwork of a wind up
>tower?
>
>Our tower has 4 sections and is of the type where all sections raise at once
>with a single cable pulley system.
>The Machine is a Nokia BRS150 using a Sinclair Duplexer on 145.7625/1625
>Antenna is Jaybeam Folded Dipole with its own RG214 tail into 60 ft of
>LDF450.
>
>When you shake the trailer mounted tower there is severe crackling on weak
>signals. The three stays have been
>tightened up as far as possible.
>Any Ideas on how to kill this noise guys?
I help maintain a system using a similar tower configuration. Right now we
have no desense problems at all. The duplexer has 3 pass-notch cans on the
RX, and 2 pass-notch cans + 1 pass only on the TX. The antenna is the 8
ft. TRAM dual-band sold by Repeater-Builder, & it's mounted ~15 ft. above
the top of the tower on a mast.
IMO the key to eliminating desense when using a less-than-ideal tower is to
keep the TX noise to a minimum, raise the antenna well above the top of the
tower to prevent coupling to the loose sections, and choose an antenna
that's well decoupled from the feedline for the same reason; apparently the
TRAM does well in this regard. I'm not familiar with the "Jaybeam folded
dipole" but if it has no balun, then the problem could be RF flowing down
your feedline & coupling into the tower.
Bob NO6B
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