Hi All,
A very Happy New Year to you all on the R-B list!
I have a couple of questions which I was wondering if anyone else out there
had any experience with.
I run a 50MHz repeater in Somerset SW England, but it is troubled by two
things......
First, I'm using a shared commercial mast and so antenna space is limited.
The repeater uses a single dipole antenna and a WB5WPA type Heliax duplexer.
I carried out the procedure described by Kevin on the RB web site to asses
the effective sensitivity of the repeater and was amazed at the results! The
effective sensitivity at my site is around -100dBm! So although my Rx is
good for -117dBm for 12dB SINAD the mobiles have a hard time getting in,
although they can hear the repeater's 22W output fine.
With a weak signal, all sorts of "birdies" can be heard in the background
instead of a nice smooth white noise that you'd expect from a weak signal.
So my first question is has anyone any experience or thoughts on using a
device like the MFJ-1026 noise canceller or any other tricks to improve the
receive situation? Or is this just "how it is" on 50MHz?
Secondly, when the wind blows, which it frequently does on this exposed
site, I am affected by the good ol' rusty bolt effect (or duplexer hash)
which I am aware of the causes / reasons for but wondered if anyone had any
experience of tracing this kind of problem to find the offending "bolt"
whatever it turns out to be! There's a load of disused antennas on the mast
and some with their cut off feeder tails flapping so that was where I was
going to start first but it would be great to be able to positively identify
the offending item somehow.
Thanks in advance for any replies.
Best wishes to all,
Matt
G4RKY.
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