[amsat-bb] Intermittent loss of full-duplex with Arrow, built-in-duplexer and TH-D72a

John Brier johnbrier at gmail.com
Fri Aug 19 18:11:55 UTC 2016

I'm only running 5 watts. Just using my Kenwood TH-D72a HT.

73, John Brier KG4AKV

On Fri, Aug 19, 2016 at 2:05 PM, R.T.Liddy <k8bl at ameritech.net> wrote:
> John,
> How much power are you running? Are you overheating
> the duplexer?
> GL/73,    Bob  K8BL
> ________________________________
> From: John Brier <johnbrier at gmail.com>
> To: AMSAT BB <amsat-bb at amsat.org>
> Sent: Friday, August 19, 2016 1:48 PM
> Subject: [amsat-bb] Intermittent loss of full-duplex with Arrow,
> built-in-duplexer and TH-D72a
> For the third time I've lost the ability to hear myself on the
> downlink of SO-50 using this setup. This was on today's 1521 UTC SO-50
> pass.
> In the past I had what appeared to be very similar behavior with a
> different arrow antenna, no duplexer and two radios. I troubleshot
> that issue to the screw in the gamma match coming lose which caused
> high SWR.
> In this case I tested the SWR with my MFJ-259B SWR analyzer and it was
> 1.1:1 and X=45-55 across almost the entire band.
> I actually was able to hear myself in the beginning of the pass and
> then it got worse until the point where I could not hear myself for
> the rest of the pass.
> Actually, in this case, unlike the other two times where I wasn't able
> to hear myself on the downlink I had another unusual behavior which
> was I *WAS* able to hear myself but it was extremely loud and
> distorted. This happened maybe twice in the middle of the pass and
> then after that I just couldn't hear myself when I transmitted.
> When I was able to hear myself very loud and distorted I felt it
> wasn't how I was getting into the bird, but somehow my radio was
> demodulating my 2 meter transmission. I confirmed with W4FS who was
> also on this pass that my audio never sounded odd.
> Very annoying and my only guess as to what could be causing this is
> some sort of external interference occasionally getting into my radio.
> Any ideas?
> 73, John Brier KG4AKV
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