> -----Original Message-----
> From: skipp025
>
> I've seen some of the other posts. You should be running
> a dual port circulator in addition to the proper duplexer.
Well, I don't necessarily disagree with using an isolator/harmonic filter.
However, the isolator will not keep 800MHz signals from getting to the
transmitter of the 2m repeater. I'm sure the harmonic filter may reduce the
800 levels some but the isolator isn't going to stop it. Of course, an
isolator will keep other VHF signals from getting back through it but I
don't have any VHF signals that are a problem. The duplexer is a new TX/RX
4 can vari-notch. I've added bandpass cavities on the rx & tx side between
the duplexer & repeater.
> You mention the 7/8 line is used. If you remove the
> connector from any end and the line is not shinny, clean
> the oxide off with a brass brush and replace the connector
> back on the cable. If the oxide color is really dark, you
> have moisture leakage in the cable and that's really bad
> news.
I'd don't know exactly how old it is but it is in "good shape" according to
the tower crew. It was previously used by a law enforcement agency before
they switched to the 800 system.
> If the PD220-2 antenna is over 10 years old, consider
> trying a swap out. I have replaced a number of aged PD
> antennas, which (along with station masters) can become
> IMD generators when placed in modest proximity to other
> antennas (and metal objects).
I purchased the PD220-2 antenna new late last year. It was drop shipped
directly from Celwave.
I installed a new polyphaser at the entry port but I haven't tried taking
it out of the circuit to see if it's contributing to the problem. Has
anyone seen a polyphaser do bad things?
> You can measure the system desense of the terminated
> feed, which will provide additional clues.
Good idea.
> You should try for min 1/4 wave spacing (at vhf) from
> the 800Mhz antennas, where possible.
The closest antenna to the PD220 is about 4 to 5 feet away.
> cheers
> skipp
>
> www.radiowrench.com
>
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