KX3 TX calibration failure on 52 MHz

The problem is the KX3 TX calibration is failing on 52 MHz at 4.0 W. I
would appreciate some advice on how to proceed with diagnosis and
correction.

First the basic background information: KX3 #8094. Firmware versions:
MCU = 2.33, MCU = 1.33. I'm running the KX3 configuration utility Ver.
1.14.4.11 on Linux Mint 17.2
[uname -a => 3.16.0-38-generic #52~14.04.1-Ubuntu SMP Fri May 8 09:43:57
UTC 2015 x86_64 x86_64 x86_64 GNU/Linux ].

To calibrate I did the following:

I attached a suitable 100W dummy load to the KX3. Then I ran the KX3
configuration utility. I executed the TX Calibration Gain. It runs fine
with no errors until it reaches 52 MHz. The relevant lines with the
failure message on the computer screen are:

    Calibrating 52.000 MHz
    TxGainStartTune Invalid response to "TQ;"
    Calibration failed

I then decided to try the TX calibration instructions in the KX3 manual.
As with the KX3 utility all went well except for the 4.0 W at 52 MHz
test. When I got to 4.0 W on 52 MHz it appeared that the output was
stable. That is the 4.0 W was holding steady. When I pressed the button
to turn off the tuning the message in VFO A displayed was "d=017." The
message in VFO B was "ERR TXG." I repeated the test at 4.0 W. The
message in VFO B stayed the same. The message in VFO A changed to
"d=042." A third attempt produced "d=046" message in VFO A. VFO B had
the same "ERR TXG" message.

I then ran the test at 6.0 W. There was no error. The error does not
suggest what to do next. Any advice would be appreciated.

Thanks all,

Tuck, W6TUK
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[Don Wilhelm-4]

Tuck,

Do you know for sure your dummy load is a good 50 ohm load at 6 meters?  
It is always good to check that with an antenna analyzer.
Try repeating the TX Gain Calibration on 52 MHz manually from the menu.
If it completes both 4 and 6 watts without complaint, you are 'good to go'.

73,
Don W3FPR

On 9/4/2015 11:30 AM, Tuck Watkins wrote:

> The problem is the KX3 TX calibration is failing on 52 MHz at 4.0 W. I
> would appreciate some advice on how to proceed with diagnosis and
> correction.
>
>
>
> I attached a suitable 100W dummy load to the KX3. Then I ran the KX3
> configuration utility. I executed the TX Calibration Gain. It runs fine
> with no errors until it reaches 52 MHz. The relevant lines with the
> failure message on the computer screen are:
>
>      Calibrating 52.000 MHz
>      TxGainStartTune Invalid response to "TQ;"
>      Calibration failed
>
> I then decided to try the TX calibration instructions in the KX3 manual.
> As with the KX3 utility all went well except for the 4.0 W at 52 MHz
> test. When I got to 4.0 W on 52 MHz it appeared that the output was
> stable. That is the 4.0 W was holding steady. When I pressed the button
> to turn off the tuning the message in VFO A displayed was "d=017." The
> message in VFO B was "ERR TXG." I repeated the test at 4.0 W. The
> message in VFO B stayed the same. The message in VFO A changed to
> "d=042." A third attempt produced "d=046" message in VFO A. VFO B had
> the same "ERR TXG" message.
>
> I then ran the test at 6.0 W. There was no error. The error does not
> suggest what to do next. Any advice would be appreciated.
>
> Thanks all,
>
> Tuck, W6TUK
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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[w7hd]

Also check your cable to the dummy load.   I had exactly the same
symptoms and it was due to a poor ground on the coax.

Ron W7HD


Tuck Watkins wrote:

> The problem is the KX3 TX calibration is failing on 52 MHz at 4.0 W. I
> would appreciate some advice on how to proceed with diagnosis and
> correction.
>
> First the basic background information: KX3 #8094. Firmware versions:
> MCU = 2.33, MCU = 1.33. I'm running the KX3 configuration utility Ver.
> 1.14.4.11 on Linux Mint 17.2
> [uname -a =>  3.16.0-38-generic #52~14.04.1-Ubuntu SMP Fri May 8 09:43:57
> UTC 2015 x86_64 x86_64 x86_64 GNU/Linux ].
>
> To calibrate I did the following:
>
> I attached a suitable 100W dummy load to the KX3. Then I ran the KX3
> configuration utility. I executed the TX Calibration Gain. It runs fine
> with no errors until it reaches 52 MHz. The relevant lines with the
> failure message on the computer screen are:
>
>      Calibrating 52.000 MHz
>      TxGainStartTune Invalid response to "TQ;"
>      Calibration failed
>
> I then decided to try the TX calibration instructions in the KX3 manual.
> As with the KX3 utility all went well except for the 4.0 W at 52 MHz
> test. When I got to 4.0 W on 52 MHz it appeared that the output was
> stable. That is the 4.0 W was holding steady. When I pressed the button
> to turn off the tuning the message in VFO A displayed was "d=017." The
> message in VFO B was "ERR TXG." I repeated the test at 4.0 W. The
> message in VFO B stayed the same. The message in VFO A changed to
> "d=042." A third attempt produced "d=046" message in VFO A. VFO B had
> the same "ERR TXG" message.
>
> I then ran the test at 6.0 W. There was no error. The error does not
> suggest what to do next. Any advice would be appreciated.
>
> Thanks all,
>
> Tuck, W6TUK
> ______________________________________________________________
> 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]
>
>

--
OMISS#9898 Linuxuser#415320 NAQCC#7587
My homepage: http://w7hd.net

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Don, Ron, and Bernhard,

Thank you for responding.  I now have a calibrated KX3. But I'm
uncertain if it is sufficient. Nor do I know exactly what has caused the
problem. It suspect the problem arose because of the cable or connector
from the dummy load to the KX3 was not-quite-right. If you have any
other theories I would appreciate hearing them.

Here is what I did.

In the original transmit calibration I used an MFJ Model J 280-C dummy
load .  As suggested, I tested the MFJ dummy load at 52 MHz with an
MFJ-269 SWR Analyser.  It had an SWR of 1.1 (with R=53 X=3) at 52.0 MHz.
While executing the KX3 "Manual Transmit Gain Calibration" the SWR shown
at the same frequency was 1.6 at 4.0W. The calibration produced the same
error as before.  But note that the value of "d" is always a different
number.

I checked the SWR of the Elecraft DL1 that I built when assembling my
K2. It tested at an SWR of 1.1 (with R=54 and X=4.) Running the manual
TX calibration the SWR on the KX3 was 1.4. The calibration failed with
the same error message as with the MFJ dummy load.

Both of the calibrations above were done with an antenna cable purchased
from Elecraft. So, I repeated the TX Calibration on the KX3 using a
different cable from my spares box. The SWR with both dummy loads was
the same but the test passed with the DL1 and not the MFJ.

Then I repeated the calibration with other cables. About half of these
calibrations done with the the MFJ and the DL1 failed with both dummy
loads. However, using two other cables the calibrations with the DL-1
passed but not with the MFJ. Then, with two more cables the MFJ
calibration passed and the DL-1 calibration failed.

Note that the MFJ has a PK-259 connector and the DL-1 has a BNC
connector. Since the cables I used for the calibrations vary as to which
connector combination they have I was forced to use adaptors. I suspect
the adaptors may not quite be up to snuff.

So the calibration succeeds with some combination of cable and DL1 dummy
load or MFJ dummy load.

Tuck, W6TUK


On 09/04/2015 01:14 PM, Don Wilhelm wrote:

> Tuck,
>
> Do you know for sure your dummy load is a good 50 ohm load at 6
> meters?  It is always good to check that with an antenna analyzer.
> Try repeating the TX Gain Calibration on 52 MHz manually from the menu.
> If it completes both 4 and 6 watts without complaint, you are 'good to
> go'.
>
> 73,
> Don W3FPR
>
> On 9/4/2015 11:30 AM, Tuck Watkins wrote:
>> The problem is the KX3 TX calibration is failing on 52 MHz at 4.0 W. I
>> would appreciate some advice on how to proceed with diagnosis and
>> correction.

[snip]
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