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

[John Brier]

Compare my recording:
https://www.dropbox.com/s/rt6lashyisefmhl/KG4AKV_-_SO-50_-_2016-08-18_-_1521_UTC.mp3?dl=0

To Clayton's recording:

https://www.dropbox.com/s/9rgwalksajpz2br/Recording_from_Clayton_W5PFG.mp3?dl=0

Best done in Audacity or another DAW/audio editing app. Start his
recording approximately 11-12 seconds after mine.

You can hear the other FM transmissions at 03:30, 03:55 (and in
particular 03:58) and 05:28

Here is my partial log of the pass:

Nothing until 01:55
02:14 N8IUP EN81 CONTACTED
02:51 K8OE
03:05 K8OE
03:30 something on my recording that isn't on Clayton's
03:55 "", in particular right at 3:58
03:51 K8OE CONTACTED
04:06 N1MDJ EM66 CONTACTED
04:25 W4FS
04:
05:10 KC3BPM FM19 CONTACTED
05:28 something on my recording that isn't on Clayton's
05:49 DISTORTION
08:02 DOPPLER ADJUSTMENT SOUNDS WEIRD
08:24 XE1AY/P
08:43 KO4MA calls XE1AP/P
10:32 KO4MA EL88 CONTACTED - LOSS of FULL DUPLEX
12:50 ????
13:03 KO4MA tells me I'm still in there
13:07 9Y4PX
13:14 GET EM JOHN
13:19 9Y4PX


73, John Brier KG4AKV

On Fri, Aug 19, 2016 at 2:46 PM, John Brier <johnbrier at gmail.com> wrote:
> I may have found the cause of the distortion, and another bit of helpful info:
>
> I got a copy of the audio of the pass from someone else and I'm
> comparing it to mine. When I am transmitting there are at least three
> places where I can hear other transmissions, clearly different FM
> transmissions of other people talking. At one point I even hear a
> roger beep like sound followed by another voice. That could just be a
> symptom of whatever is causing the desense though.
>
> Regarding this:
>
> On Fri, Aug 19, 2016 at 2:12 PM, James Duffey <jamesduffey at comcast.net> wrote:
>> If I had to guess, I would say that you have a feed line problem, either a short or open.
>>
>> Another option may be a poor connection or a short in the diplexer. - Duffey KK6MC
>>
>
> I have suspected the duplexer myself. There is only one connection
> from it to the radio. No adapters. The feedline from the duplexer has
> an SMA connector and screws right onto the SMA on the Kenwood TH-D72a.
> Still it could be the BNC connectors that go to the antenna.
>
> I asked the owner of Arrow antenna about the possibility of this issue
> being caused by the duplexer and he was not aware of that ever
> happening before.
>
> :-/
>
>
> On Fri, Aug 19, 2016 at 2:12 PM, James Duffey <jamesduffey at comcast.net> wrote:
>> If I had to guess, I would say that you have a feed line problem, either a short or open.
>>
>> Another option may be a poor connection or a short in the diplexer. - Duffey KK6MC
>>
>> On Aug 19, 2016, at 11:48 AM, John Brier <johnbrier at gmail.com> wrote:
>>
>>> 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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>>