[amsat-bb] Diplexer, Arrow ant, 2 handhelds question

[Don KB2YSI]

I will have to try this with my IC7100 to see if it makes a difference.

On Tue, Mar 26, 2019, 13:14 Stephen E. Belter <seb at wintek.com> wrote:

> Steve,
>
> *If* the problem is 3rd harmonics from the 2 m transmitter, then what you
> did should have helped.  Adding a 50-ohm terminator might improve the
> attenuation of the 3rd harmonic.
>
> A more common problem is that the 70 cm receiver can't handle the 2 m
> transmitted signal because the receiver doesn't attenuate the 2 m signal
> sufficiently.  (The AGC on the radio hears the 2 m signal, attenuates the
> whole 70 cm band, and you don't hear the satellite.)  By using the Arrow
> diplexer as a 2 m band reject filter, you may solve your problem.
>
> For a better explanation see, Tony AA2TX's article here:
> https://www.amsat.org/a-simple-desense-filter-for-mode-j-satellites/
>
> So try your experiment again, but connect the antenna end of the diplexer
> to the 70 cm antenna and the 70 cm radio end of the diplexer to your
> receiver.
>
> 73, Steve N9IP
> --
> Steve Belter, seb at wintek.com
>
>
>
> On 3/26/19, 12:18 PM, "AMSAT-BB on behalf of skristof at etczone.com" <
> amsat-bb-bounces at amsat.org on behalf of skristof at etczone.com> wrote:
>
>     Today, on the SO-50 pass, I tried using the Arrow diplexer (duplexer?)
>     to enable full-duplex using two handhelds. As most on this forum know,
>     if you use two handhelds with the Arrow antenna, the third harmonic of
>     the 2m uplink will desense the 70cm handheld, so you can't hear
>     yourself.
>
>     So, I hooked up what is normally the antenna end of the diplexer to the
>     2m uplink radio and the 2m radio end of the diplexer to the 2m part of
>     the Arrow antenna. My hope was that this would suppress the third
>     harmonic of the 2m uplink enough so that it wouldn't desense the 70cm
>     handheld. The 70cm radio end of the diplexer was left unconnected.
>
>     It didn't seem to work. I made contacts but I still didn't hear myself
>     on 70cm.
>
>     Just wondering if anyone else has tried this and what results you got.
>
>     Steve AI9IN
>
>     EM79ji
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