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K3 false SWR indication with SSB

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K3 false SWR indication with SSB

My k3 flashes a higher swr indication with ssb voice peaks than with a steady carrier.

If using an antenna with 1:1 SWR the bar graph flashes the first segment. If swr is 1.5:1
all the segments illuminate on voice peaks, as if swr was greater than 3:1. To reduce the
uncertainty introduced by my antennas, I connected a 50 ohm load after an external tuner
so I could create the 1.5:1 SWR, and got the same results.

I assume this is a benign problem and likely caused by the non simultaneous sampling
of FWD and REV power by the CPU.

However, if no one else sees this I'll do some more checking.

FW 4.81/2.83 and TX Gain Cal done recently.

Mark. N2QT
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Fred Townsend-2

Re: K3 false SWR indication with SSB

Mark I have not seen your problem so I tend to discount your explanation. It sounds like something is breaking down. Perhaps bad coax, antenna, insulator, or lightning arrestor. You could test with a TDR (Time Domain Reflectometer) or Hipot tester. If you lack the equipment connect a dummy load to the K3 and test. If that passes your problem is not in the K3.
73
Fred, AE6QL

-----Original Message-----

>From: Mark N2QT via Elecraft <[hidden email]>
>Sent: Aug 19, 2014 12:15 PM
>To: "[hidden email]" <[hidden email]>
>Subject: [Elecraft] K3 false SWR indication with SSB
>
>My k3 flashes a higher swr indication with ssb voice peaks than with a steady carrier.
>
>If using an antenna with 1:1 SWR the bar graph flashes the first segment. If swr is 1.5:1
>all the segments illuminate on voice peaks, as if swr was greater than 3:1. To reduce the
>uncertainty introduced by my antennas, I connected a 50 ohm load after an external tuner
>so I could create the 1.5:1 SWR, and got the same results.
>
>I assume this is a benign problem and likely caused by the non simultaneous sampling
>of FWD and REV power by the CPU.
>
>However, if no one else sees this I'll do some more checking.
>
>FW 4.81/2.83 and TX Gain Cal done recently.
>
>Mark. N2QT

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Guy Olinger K2AV

Re: K3 false SWR indication with SSB

Peak SSB power can exceed the 100 watts if all the calibrations are
not current. You should very carefully make sure that the actual peak
power and the steady CW power are the same. Make sure that all the
manual's calibrations have been run. In order to run right, the
firmware needs to know a small pile of things about your particular K3
to make performance standard. "Recently" does not give me warm fuzzies
about being adjusted to spec.

I have found that sometimes doing a firmware update will unglue some
of the stored data in the K3, both calibration and others, despite
Elecraft's protestations that shouldn't happen. Doesn't hurt to rerun
the ENTIRE set of calibration exercises every couple of years. Not
with every firmware update for sure, but whenever an update is
followed by some previously unnoticed quirkiness I'll run them. That
way I'm on the clean side of things if I report a quirk to be related
to an update. If the quirk was cleaned up by a calibration, one can
be assured that Big E will never be able to duplicate it and figure
out what was going on if I reported it without recalibration. I really
don't want to waste any of their time. They're more interesting when
they're working on their projects.

73, Guy K2AV

On Tue, Aug 19, 2014 at 3:33 PM, Fred Townsend <[hidden email]> wrote:

>
> Mark I have not seen your problem so I tend to discount your explanation. It sounds like something is breaking down. Perhaps bad coax, antenna, insulator, or lightning arrestor. You could test with a TDR (Time Domain Reflectometer) or Hipot tester. If you lack the equipment connect a dummy load to the K3 and test. If that passes your problem is not in the K3.
> 73
> Fred, AE6QL
>
> -----Original Message-----
>>From: Mark N2QT via Elecraft <[hidden email]>
>>Sent: Aug 19, 2014 12:15 PM
>>To: "[hidden email]" <[hidden email]>
>>Subject: [Elecraft] K3 false SWR indication with SSB
>>
>>My k3 flashes a higher swr indication with ssb voice peaks than with a steady carrier.
>>
>>If using an antenna with 1:1 SWR the bar graph flashes the first segment. If swr is 1.5:1
>>all the segments illuminate on voice peaks, as if swr was greater than 3:1. To reduce the
>>uncertainty introduced by my antennas, I connected a 50 ohm load after an external tuner
>>so I could create the 1.5:1 SWR, and got the same results.
>>
>>I assume this is a benign problem and likely caused by the non simultaneous sampling
>>of FWD and REV power by the CPU.
>>
>>However, if no one else sees this I'll do some more checking.
>>
>>FW 4.81/2.83 and TX Gain Cal done recently.
>>
>>Mark. N2QT
>
> ______________________________________________________________
> 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]

Elecraft mailing list

Re: K3 false SWR indication with SSB

In reply to this post by Elecraft mailing list

Mark,

This was addressed several months ago concerning the KX3. When the software gets ready to display SWR, it reads forward power, and a fraction of a second later, reverse power. Since voice peaks go up and down, the displayed SWA will not be accurate unless you use a steady signal.

Mark
KE6BB

-------- Original message --------
From: Mark N2QT via Elecraft <[hidden email]>
Date:08/19/2014 12:15 PM (GMT-08:00)
To: [hidden email]
Cc:
Subject: [Elecraft] K3 false SWR indication with SSB

My k3 flashes a higher swr indication with ssb voice peaks than with a steady carrier.

If using an antenna with 1:1 SWR the bar graph flashes the first segment. If swr is 1.5:1
all the segments illuminate on voice peaks, as if swr was greater than 3:1. To reduce the
uncertainty introduced by my antennas, I connected a 50 ohm load after an external tuner
so I could create the 1.5:1 SWR, and got the same results.

I assume this is a benign problem and likely caused by the non simultaneous sampling
of FWD and REV power by the CPU.

However, if no one else sees this I'll do some more checking.

FW 4.81/2.83 and TX Gain Cal done recently.

Mark. N2QT
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
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]