Heh,thats typical! Sounds like an expensive fix. I am still fighting
with a crazy shifting interference that only appears when I transmit,may
have to abandon 2 meter duplex and run just remote receivers.Now to find
a free site.....yeah,RIGHT!
Kevin Custer wrote:
>I believe he said he was troubleshooting a duplex noise issue; which
>doesn't necessarily mean desense. I have a repeater on a commercial
>tower in which AC power (for the light on top) goes up a rusty metal
>conduit. When the wind blows, the conduit makes duplex noise *if* I'm
>using a common antenna. If I separate the repeater on two antennas, the
>problem disappears, or, if the tower ices over, it disappears. Now
>trying to figure out how to keep the tower iced over cheaply during the
>summer months.... <grin>
>
>Kevin
>
>Q wrote:
>
>
>
>>You would gain much more isolation by separating them vertically. Side
>>by side would also mess up the pattern. Not familiar with that
>>duplexer,but if it has a Tee at the antenna port,simply remove it and
>>connect the two antennas where the Tee was. This >may< throw the tuning
>>off some but is worth a try. Why do you feel the need to split the
>>antennas? Having desense problems? 73,Lee,N3APP
>>
>>k3phl wrote:
>>
>>
>>
>>
>>
>>>Hello all,
>>>
>>>I am considering running split antennas at my 220 MHz site in
>>>Philadelphia as a test to increase sensitivity and troubleshoot a
>>>duplex noise issue. The machine is currently a modifed Motorola
>>>Micor using a TX/RX 4 can duplexer, DCI bandpass filter in the RX
>>>leg, and a Comet Super 22 (220) base antenna.
>>>
>>>I am considering running separate Super 22 antennas 12 feet apart
>>>horizontally. One feedline run will go from the transmitter direct
>>>to the TX antenna. The other feedline run will run from the receiver
>>>to RX port of duplexer, common port of duplexer to 220 bandpass
>>>filter and then to the RX antenna. The TX port of the duplexer will
>>>remain unconnected.
>>>
>>>I expect the duplexer to act as a 2 can deep notch, eliminating the
>>>transmitter from the receiver with the TX port open. I assume the TX
>>>rejection in the receiver line should improve and the resulting RX
>>>sensitivity should improve since the transmitter has been reduced to
>>>a strong near field instead of RF on the same line. Is this the
>>>correct theory of using a duplexer in a split antenna site and if so,
>>>should the TX port be left unconnected or capped with a 50 ohm load?
>>>
>>>Thanks in advance,
>>>
>>>Steve
>>>K3PHL
>>>
>>>
>>>
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