[amsat-bb] Question about duplexer as a high-pass filter

[Robert Bankston]

Steve,
I have had great success using a diplexer on the VFH side to eliminate desense on V/u satellites.  I do not use a dummy load/terminator on the UHF port. Recently, I switched to a Mini-Circuits BLP-200+ as it has a smaller form factor.  Note, the BLP-200+ has an advertised  0.5W power limitation.  I have used mine with 10W output with no smoke released, yet.  Your mileage may vary.
73,Robert, KE4AL    On Sunday, November 10, 2019, 05:26:17 PM CST, Bob via AMSAT-BB <amsat-bb at amsat.org> wrote:  
 
 Hi Steve,

I asked myself a similar question and decided to measure things both
terminated and un-terminated.  Bottom line is you want to terminate that
unused port.

Here is a story on my website:  https://wb4son.com/wpblog/?p=2828

73, Bob, WB4SON

On Sun, Nov 10, 2019 at 6:18 PM AI9IN via AMSAT-BB <amsat-bb at amsat.org>
wrote:

> My satellite rig is two HTs running to an Arrow antenna. Trying my best
> to operate full duplex. When operating V/U I am using the UHF side of
> the Arrow duplexer as a high pass filter between the UHF antenna feed
> point and the UHF HT to keep the 2 m transmit signal from desensing the
> UHF receive.
>
> But it only sort of works.
>
> This set up leaves the VHF end of the duplexer open and just hanging.
> Would this setup work better with a 50 ohm load across that empty
> connection? (Sorry if this is a dumb or elementary question, but I'll
> never find out if I don't ask.)
>
> All helpful insights are welcome.
>
> Steve AI9IN
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_______________________________________________
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to all interested persons worldwide without requiring membership. Opinions expressed
are solely those of the author, and do not reflect the official views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb