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

[skristof at etczone.com]

This worked! I put the filter on the 70 cm side of the "rig" and I was
full duplex on the next SO-50 pass. Thanks for the great tip.  

I also appreciate you roving to a grid line and giving several of us a
"twofer". 

Steve AI9IN

On 2019-03-26 10:07, Stephen E. Belter 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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