> Numbers 1 or 4 are the more likely.
>
> He has a Quantar which is designed to live in high RF
> environments at antenna sites making #2 unlikely. Also, with
> respect to #3, the Quantar PA has a built in circulator as
> standard equipment.
OK. I missed (or maybe wasn't paying attention) that he had a Quantar.
Still, the high VSWR isn't something I'd want to live with, especially when
connected to a duplexer.
I worked on an MSR2000 installed in the upper level of a two-story
mechanical room (concrete) that suffered desense from its own antenna
(DB224) which was mounted to the exterior of wall, maybe 15' directly above
the repeater cabinet (whoever installed it probably chose that mounting
location figuring it was the shortest cable path). Moving the antenna to
the other side of the penthouse to get another 50 feet or so of distance
from the repeater reduced the desense substantially, but didn't completely
eliminate it. Moving the repeater to the lower level did the trick. So I
wouldn't totally rule out #2 just yet, although given the equipment
complement, I agree that #1 and #4 or other external factors are more likely
(and an MSR2000 ain't no Quantar by any stretch of the imagination).
--- Jeff
> --- In Repeater-Builder@yahoogroups.com
> <mailto:Repeater-Builder%40yahoogroups.com> , "Jeff DePolo"
> <j...@...> wrote:
>
> "Seems to me the three most-likely causes of your problem are:
>
> 1. Antenna itself is bad/noisy. Substituting antennas may
> help rule this out.
>
> 2. Not enough isolation between radiating antenna and
> equipment. The 100' of horizontal separation may not be
> enough to keep the strong RF out of your equipment,
> effectively bypassing/negating the isolation your
> finely-tuned duplexer is attempting to provide.
>
> 3. Mis-match due to out-of-band antenna is causing other
> problems, possibly even transmitter going spurious. While I
> generally don't recommend using isolators or Z-matchers as
> band-aids to cure antenna ills, using one to help rule this
> out as possible cause might be helpful as a short-term experiment.
>
> 4. You mention "metal building", which conjures many bad
> memories of rooftop installations where all kinds of noise
> problems related to HVAC units, duct work, corrugated metal
> panels, metal screens/grills, ventilation stacks, cooling
> towers, etc. resulted in countless hours of time spent trying
> to reduce noise and passive intermod mixes. You're on your
> own on that one..."
>
>
>
>
>
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