K3 with KSYN3A 100Hz spurious

[Dave Johnson]

My old K3 (serial #80) with dual RX and KSYN3A upgrade synths, has
developed a fault.

A “tune up” carrier, CW transmission, AM transmission, all exhibit 100Hz
“modulation” with spurious carriers every 100Hz each side of the centre
frequency. They start around 10dB down and drop off in a similar manner to
SSB IMD products. Receive sounds fine.

The issue is not always present when the K3 is cold, it is not related to
external connections (removed all except power), nor to a power supply
(swapped it and the power lead). It is also present on low power and on all
bands.

I’ve asked Elecraft Support, no reply so far. Any ideas as to what might be
the problem?

Thanks
Dave G4AON
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[Ignacy]

At one time my old K3 with 2nd RX had a 20KHz+ wide signal on 80m, which
generated lots of "attention"
since there were two dxpeditions close by and some blamed me for not getting
ATNO. Got a "nice" screenshot from a Flex. Receive was OK. I asked the
Elecraft support for some ideas and there was not a clear answer.

I tested the radio afterwards with an SDR.  The bandwidth was getting
smaller and then everything was normal. Not sure what has happened. It must
have been the transmit path somehow influencing the synthesizer (KSYN3).

Ignacy NO9E



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[Elecraft mailing list]

Hi Dave, Still have those old synthesizers laying around.  I would start there and putt the old ones back in.  That will also force  you to disconnect and reconnect those infamous TMP coax connections.  

It is a place to start while Elecraft works you through the cue.

73, Bill-AK5X, K3 SN 00069

> On Mar 1, 2021, at 2:20 PM, Dave <[hidden email]> wrote:
>
> My old K3 (serial #80) with dual RX and KSYN3A upgrade synths, has
> developed a fault.
>
> A “tune up” carrier, CW transmission, AM transmission, all exhibit 100Hz
> “modulation” with spurious carriers every 100Hz each side of the centre
> frequency. They start around 10dB down and drop off in a similar manner to
> SSB IMD products. Receive sounds fine.
>
> The issue is not always present when the K3 is cold, it is not related to
> external connections (removed all except power), nor to a power supply
> (swapped it and the power lead). It is also present on low power and on all
> bands.
>
> I’ve asked Elecraft Support, no reply so far. Any ideas as to what might be
> the problem?
>
> Thanks
> Dave G4AON
> --
> Sent from my iPhone SE
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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[Dave Johnson]

I need to apologise to the group and to my old K3... the problem wasn’t the
K3 after all. It turned out to be my Icom IC-7300 displaying an S9 carrier
from the K3 as having 100Hz sidebands and also producing a loud buzz from
the speaker.

Feeding the 7300 with an S9 level from a signal generator showed the
problem was with the Icom. I have no idea what caused the problem which was
present before a firmware upgrade, and after upgrading to version 1.40.
Doing a full reset of the 7300 cured the problem.

73 Dave G4AON
--
Sent from my iPhone SE
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