K3 - SWR on Tx Gain Calibration

[Geoffrey Downs-2]

For some time I've been puzzled that, when doing a TX gain calibration
either manually or with the utility, the SWR displayed was 1.0:1 on all
bands except for 10m where it was 1.5:1. Yesterday my K3 (Ser. No. 266) had
a meeting with a K3 (slightly earlier Ser. No.) belonging to David G4DMP
(the owners met too!) and we found that his K3 was the same.

Now here's the interesting thing. During tx gain calibration a 50 ohm dummy
load is used and the ATU is in bypass mode. As an experiment David put his
K3's ATU in circuit on 10m and pressed ATU Tune - result (unsurprisingly)
1.0:1. He then put the ATU back into bypass mode and held Tune as one would
do in a tx gain calibration. Hey presto - 1.0:1! My K3 behaved in exactly
the same way and now always displays 1.0:1 on 10m into the dummy load with
the ATU in bypass mode.

Presumably this is something to do with the ATU not being out of circuit
when in bypass mode.

73 to all
Geoff
G3UCK

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[lstavenhagen]

For what it's worth, I definitely can't replicate this on my K3. The ATU is definitely is bypassed when I select bypass on 10M (in both ANT sockets).
Do you hear the relay clicking when you switch back and forth between bypass and inline?

73,
LS
W5QD

[Mike Reublin]

lstavenhagen wrote:
> For what it's worth, I definitely can't replicate this on my K3. The ATU is
> definitely is bypassed when I select bypass on 10M (in both ANT sockets).
> Do you hear the relay clicking when you switch back and forth between bypass
> and inline?
>
> 73,
> LS
> W5QD
>  
I had a question about bypassing the ATU a while back. If I remember
correctly (put the IF in caps), I was told it is not completely out of
the circuit when it's bypassed.
Don? Lyle? Wayne?

73, Mike NF4L

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[Bill VanAlstyne W5WVO]

FWIW, my K3 does not audibly activate any relays when switching between AUTO
and BYPASS modes on 6 meters -- but on every other band, it does, you can
hear it. And the ATU does engage and match on 6 meters when not bypassed.
Curious.

Bill W5WVO


--------------------------------------------------
From: "lstavenhagen" <[hidden email]>
Sent: Wednesday, May 05, 2010 9:39 AM
To: <[hidden email]>
Subject: Re: [Elecraft] K3 - SWR on Tx Gain Calibration

>
> For what it's worth, I definitely can't replicate this on my K3. The ATU
> is
> definitely is bypassed when I select bypass on 10M (in both ANT sockets).
> Do you hear the relay clicking when you switch back and forth between
> bypass
> and inline?
>
> 73,
> LS
> W5QD
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/K3-SWR-on-Tx-Gain-Calibration-tp5008783p5009531.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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>
>

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[Bob Cunnings NW8L]

When in doubt, search the archives!

http://www.mail-archive.com/elecraft@.../msg69011.html

http://www.mail-archive.com/elecraft@.../msg84916.html

Bob NW8L


On Wed, May 5, 2010 at 11:07 AM, Mike <[hidden email]> wrote:

> lstavenhagen wrote:
>> For what it's worth, I definitely can't replicate this on my K3. The ATU is
>> definitely is bypassed when I select bypass on 10M (in both ANT sockets).
>> Do you hear the relay clicking when you switch back and forth between bypass
>> and inline?
>>
>> 73,
>> LS
>> W5QD
>>
> I had a question about bypassing the ATU a while back. If I remember
> correctly (put the IF in caps), I was told it is not completely out of
> the circuit when it's bypassed.
> Don? Lyle? Wayne?
>
> 73, Mike NF4L
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[Geoffrey Downs-2]

Thanks for the links Bob. I thought I remembered something like that.
Thanks also to others who have commented.

Maybe the ATU needs to look at a 50 ohm load at some point in its youth in
order to learn what residual values to leave in circuit when in bypass. I
use 10m only very rarely so it's likely that I have never shown the ATU a 50
ohm load on that band. OTOH could it be a malfunction somewhere that is
being compensated for by ATU residual  values in bypass? I'm not noticing
any other oddities though.

By the way, Istavenhagen, the relay does click when I change to and from
bypass. Even on 6m, Bill (W5WVO).

73 to all

Geoff
G3UCK

----- Original Message -----
From: "Bob Cunnings" <[hidden email]>


> When in doubt, search the archives!
>
> http://www.mail-archive.com/elecraft@.../msg69011.html
>
> http://www.mail-archive.com/elecraft@.../msg84916.html
>

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[lstavenhagen]

Well now that I understand what bypass actually is, it makes more sense to me too. It sounds kind of like the manual method of "bypassing" the ATU in the K2, but just automatic. Neato!

73,
LS
W5QD

[Bill VanAlstyne W5WVO]

Interesting, Geoff. Could it be that, since my 6m antenna array is resonant
and shows 1:1 SWR both on the K3 and on an external power meter, and both
BEFORE and AFTER I recently installed the KAT3 tuner, maybe the KAT3 doesn't
actually see any difference in matching requirements between AUTO and BYPASS
and so therefore doesn't need to switch anything? Nothing to complain about,
everything works great here on 6m, but it's curious that I don't hear
anything switching. I'll bet it has to do with the fact that my antenna load
is flat. Thanks to the MFJ-259B for that. :-)

Bill W5WVO

--------------------------------------------------
From: "Geoffrey Downs" <[hidden email]>
Sent: Thursday, May 06, 2010 6:15 AM
To: "Bob Cunnings" <[hidden email]>; <[hidden email]>
Subject: Re: [Elecraft] K3 - SWR on Tx Gain Calibration

> By the way, Istavenhagen, the relay does click when I change to and from
> bypass. Even on 6m, Bill (W5WVO).
 


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