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KX3 atu anomalies - or it is me.

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w6ldm

KX3 atu anomalies - or it is me.

Hi,

I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W

Am I missing something. I did a search on the reflector but didn't show anything.

Thank you in advance for your help

Luca
W6LDM
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Don Wilhelm-4

Re: KX3 atu anomalies - or it is me.

Lucia,

You say that you had an SWR of 1.4, then used the ATU which lowered the
SWR to 1.0
OK, That was on the KX3 display.

Please tell us where you were reading the continued 1.4 SWR. The KX3
display does not show the SWR during transmit - only during a TUNE.
The SWR shown externally to the KX2 ATU will not change, so if you are
using an external device, you will not see any change in the SWR reading.

The KX3 ATU will reduce the SWR between the KX3 output PA and the input
to the KXATU3 to the value shown during on the KX3 display during a
TUNE, but the SWR between the KXATU3 and the antenna (as measured by an
external device) will not change.

73,
Don W3FPR

On 9/18/2012 8:14 PM, luca de marinis wrote:
> Hi,
>
> I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W
>
> Am I missing something. I did a search on the reflector but didn't show anything.
>
> Thank you in advance for your help
>
>

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w6ldm

Re: KX3 atu anomalies - or it is me.

Hi Don, I read the 1.4 SWR on my MFJ 259b then tuned with the KX3 atu to 1.0

On transmitting the swr graph showed peaks near to 2 and if I press the XMIT (tune) the reading is about 1.4 same as without ATU.

Luca

On Sep 18, 2012, at 7:12 PM, Don Wilhelm <[hidden email]> wrote:

> Lucia,
>
> You say that you had an SWR of 1.4, then used the ATU which lowered the
> SWR to 1.0
> OK, That was on the KX3 display.
>
> Please tell us where you were reading the continued 1.4 SWR. The KX3
> display does not show the SWR during transmit - only during a TUNE.
> The SWR shown externally to the KX2 ATU will not change, so if you are
> using an external device, you will not see any change in the SWR reading.
>
> The KX3 ATU will reduce the SWR between the KX3 output PA and the input
> to the KXATU3 to the value shown during on the KX3 display during a
> TUNE, but the SWR between the KXATU3 and the antenna (as measured by an
> external device) will not change.
>
> 73,
> Don W3FPR
>
> On 9/18/2012 8:14 PM, luca de marinis wrote:
>> Hi,
>>
>> I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W
>>
>> Am I missing something. I did a search on the reflector but didn't show anything.
>>
>> Thank you in advance for your help
>>
>>
>
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>
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Don Wilhelm-4

Re: KX3 atu anomalies - or it is me.

Lucia,

Is your KX3 menu parameter for the ATU MD set to "AUTO" If not, the
results may be as you have experienced.

73,
Don W3FPR

On 9/18/2012 10:36 PM, luca de marinis wrote:

> Hi Don, I read the 1.4 SWR on my MFJ 259b then tuned with the KX3 atu to 1.0
>
> On transmitting the swr graph showed peaks near to 2 and if I press the XMIT (tune) the reading is about 1.4 same as without ATU.
>
> Luca
>
>
>
>
> On Sep 18, 2012, at 7:12 PM, Don Wilhelm <[hidden email]> wrote:
>
>> Lucia,
>>
>> You say that you had an SWR of 1.4, then used the ATU which lowered the
>> SWR to 1.0
>> OK, That was on the KX3 display.
>>
>> Please tell us where you were reading the continued 1.4 SWR. The KX3
>> display does not show the SWR during transmit - only during a TUNE.
>> The SWR shown externally to the KX2 ATU will not change, so if you are
>> using an external device, you will not see any change in the SWR reading.
>>
>> The KX3 ATU will reduce the SWR between the KX3 output PA and the input
>> to the KXATU3 to the value shown during on the KX3 display during a
>> TUNE, but the SWR between the KXATU3 and the antenna (as measured by an
>> external device) will not change.
>>
>> 73,
>> Don W3FPR
>>
>> On 9/18/2012 8:14 PM, luca de marinis wrote:
>>> Hi,
>>>
>>> I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W
>>>
>>> Am I missing something. I did a search on the reflector but didn't show anything.
>>>
>>> Thank you in advance for your help
>>>
>>>
>> ______________________________________________________________
>> 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
> ______________________________________________________________
> 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
>

Don Wilhelm-5

Re: KX3 atu anomalies - or it is me.

In reply to this post by w6ldm

Lucia,

The Elecraft tuner (I don't care if it is a KAT2, KAT1, KXT1 o KXAT3)
cannot change the the SWR of the antenna itself. The ATU will tune the
antenna to an acceptable SWR so the PA transistor in the transceiver
are happy. If you measure the SWR between the Tuner and the antenna,
you will not see any change. The internal tuner does change the
impedance that is seen by the PA transistors, and that is the goal of
antenna tuners.

73,
Don W3FPR

On 9/18/2012 10:36 PM, luca de marinis wrote:

w6ldm

Re: KX3 atu anomalies - or it is me.

In reply to this post by Don Wilhelm-4

Hi Don, yes I agree with you that if I measure the swr between the radio and the antenna I will have the same value I measured with the antenna analyzer.

The Automatic Tuner is installed and the mane ATU MD on AUTO

My point is:

Why do I read ON THE KX3 swr GRAPH a peak value close to 2.0 when I transmit?

Why do I read the real SWR of the antenna - in my case 1.4 - when I hold XMIT to activate TUNE?

Thanks

Luca

On Sep 18, 2012, at 7:12 PM, Don Wilhelm <[hidden email]> wrote:

Matt Maguire

Re: KX3 atu anomalies - or it is me.

In reply to this post by w6ldm

By "SWR graph", you mean the bar graph on the display of the KX3, right? If so, are you sure it is set to measure VSWR rather than compression?

If you have initiated a tuning cycle with the KXAT3, and subsequently hold the XMIT/TUNE button, and the radio reports a VSWR of 1.4, then this means that the KXAT3 has not matched the impedance of the antenna system. This would be the case, for example, is the KXAT3 was set in bypass mode.

As Don notes below, if you put an SWR meter between the KX3 and the antenna, then the KXAT3 will have no effect whatsoever on the reading of this meter (after all, the KXAT3 is matching the impedance between the antenna system and the PA stage inside the KX3, and has no effect all on the VSWR on the section of transmission line between the KXAT3 and the antenna).

If the SWR graph in your KX3 is set to read VSWR, and the KXAT3 has matched the antenna ad reported a VSWR of 1.0, and you see the SWR graph jumping around during transmit, then this could indicate flashover in the KXAT3. Normally this should only happen if the antenna system is very far away from 50 ohms. This is not likely to be the case here, if you indeed measured the VSWR of the antenna system independently with the MFJ antenna analyser, and found it only to be 1.4:1.

73, Matt VK2ACL

On 19/09/2012, at 12:36 PM, luca de marinis <[hidden email]> wrote:

> Hi Don, I read the 1.4 SWR on my MFJ 259b then tuned with the KX3 atu to 1.0
>
> On transmitting the swr graph showed peaks near to 2 and if I press the XMIT (tune) the reading is about 1.4 same as without ATU.
>
> Luca
>
>
>
>
> On Sep 18, 2012, at 7:12 PM, Don Wilhelm <[hidden email]> wrote:
>
>> Lucia,
>>
>> You say that you had an SWR of 1.4, then used the ATU which lowered the
>> SWR to 1.0
>> OK, That was on the KX3 display.
>>
>> Please tell us where you were reading the continued 1.4 SWR. The KX3
>> display does not show the SWR during transmit - only during a TUNE.
>> The SWR shown externally to the KX2 ATU will not change, so if you are
>> using an external device, you will not see any change in the SWR reading.
>>
>> The KX3 ATU will reduce the SWR between the KX3 output PA and the input
>> to the KXATU3 to the value shown during on the KX3 display during a
>> TUNE, but the SWR between the KXATU3 and the antenna (as measured by an
>> external device) will not change.
>>
>> 73,
>> Don W3FPR
>>
>> On 9/18/2012 8:14 PM, luca de marinis wrote:
>>> Hi,
>>>
>>> I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W
>>>
>>> Am I missing something. I did a search on the reflector but didn't show anything.
>>>
>>> Thank you in advance for your help
>>>
>>>
>>
>> ______________________________________________________________
>> 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
>
> ______________________________________________________________
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>
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w6ldm

Re: KX3 atu anomalies - or it is me.

Thank you Matt,

> By "SWR graph", you mean the bar graph on the display of the KX3, right? If so, are you sure it is set to measure VSWR rather than compression?
No, I read it on the SWR of course.
>
> If you have initiated a tuning cycle with the KXAT3, and subsequently hold the XMIT/TUNE button, and the radio reports a VSWR of 1.4, then this means that the KXAT3 has not matched the impedance of the antenna system. This would be the case, for example, is the KXAT3 was set in bypass mode.
It is not on bypass mode.
>
> As Don notes below, if you put an SWR meter between the KX3 and the antenna, then the KXAT3 will have no effect whatsoever on the reading of this meter (after all, the KXAT3 is matching the impedance between the antenna system and the PA stage inside the KX3, and has no effect all on the VSWR on the section of transmission line between the KXAT3 and the antenna).
I don't own an external swr meter so no, I didn't read between the radio and the antenna.
>
> If the SWR graph in your KX3 is set to read VSWR, and the KXAT3 has matched the antenna ad reported a VSWR of 1.0, and you see the SWR graph jumping around during transmit, then this could indicate flashover in the KXAT3. Normally this should only happen if the antenna system is very far away from 50 ohms. This is not likely to be the case here, if you indeed measured the VSWR of the antenna system independently with the MFJ antenna analyser, and found it only to be 1.4:1.

This seems to be the case. So is it normal or not? Any idea how to fix it?

Thanks again and I apologize for my English that apparently isn't good enough to explain what happened to me.

Cheers.

Luca

>
> 73, Matt VK2ACL
>
>
>
> On 19/09/2012, at 12:36 PM, luca de marinis <[hidden email]> wrote:
>
>> Hi Don, I read the 1.4 SWR on my MFJ 259b then tuned with the KX3 atu to 1.0
>>
>> On transmitting the swr graph showed peaks near to 2 and if I press the XMIT (tune) the reading is about 1.4 same as without ATU.
>>
>> Luca
>>
>>
>>
>>
>> On Sep 18, 2012, at 7:12 PM, Don Wilhelm <[hidden email]> wrote:
>>
>>> Lucia,
>>>
>>> You say that you had an SWR of 1.4, then used the ATU which lowered the
>>> SWR to 1.0
>>> OK, That was on the KX3 display.
>>>
>>> Please tell us where you were reading the continued 1.4 SWR. The KX3
>>> display does not show the SWR during transmit - only during a TUNE.
>>> The SWR shown externally to the KX2 ATU will not change, so if you are
>>> using an external device, you will not see any change in the SWR reading.
>>>
>>> The KX3 ATU will reduce the SWR between the KX3 output PA and the input
>>> to the KXATU3 to the value shown during on the KX3 display during a
>>> TUNE, but the SWR between the KXATU3 and the antenna (as measured by an
>>> external device) will not change.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 9/18/2012 8:14 PM, luca de marinis wrote:
>>>> Hi,
>>>>
>>>> I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W
>>>>
>>>> Am I missing something. I did a search on the reflector but didn't show anything.
>>>>
>>>> Thank you in advance for your help
>>>>
>>>>
>>>
>>> ______________________________________________________________
>>> 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
>>
>> ______________________________________________________________
>> 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
>

Matt Maguire

Re: KX3 atu anomalies - or it is me.

On 19/09/2012, at 2:47 PM, luca de marinis <[hidden email]> wrote:

>> If you have initiated a tuning cycle with the KXAT3, and subsequently hold the XMIT/TUNE button, and the radio reports a VSWR of 1.4, then this means that the KXAT3 has not matched the impedance of the antenna system. This would be the case, for example, is the KXAT3 was set in bypass mode.
> It is not on bypass mode.

Just check one more thing: in order to initiate a tuning cycle, you need to push the "ATU TUNE" button, not hold the XMIT/TUNE button. If the tuning cycle is successful, you should see an indication "1.0-1" come up on the screen. Is this what you saw?

>> If the SWR graph in your KX3 is set to read VSWR, and the KXAT3 has matched the antenna ad reported a VSWR of 1.0, and you see the SWR graph jumping around during transmit, then this could indicate flashover in the KXAT3. Normally this should only happen if the antenna system is very far away from 50 ohms. This is not likely to be the case here, if you indeed measured the VSWR of the antenna system independently with the MFJ antenna analyser, and found it only to be 1.4:1.
>
> This seems to be the case. So is it normal or not? Any idea how to fix it?

No, this is not normal. If you are quite sure that you have followed the suggestions given here and the directions in the owner's manual, then the next step would be to get in touch with Elecraft customer support, who can lead you through some more detailed troubleshooting.

73, Matt VK2ACL.
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w6ldm

Re: KX3 atu anomalies - or it is me.

On Sep 18, 2012, at 10:00 PM, Matt Maguire <[hidden email]> wrote:

>
> On 19/09/2012, at 2:47 PM, luca de marinis <[hidden email]> wrote:
>
>>> If you have initiated a tuning cycle with the KXAT3, and subsequently hold the XMIT/TUNE button, and the radio reports a VSWR of 1.4, then this means that the KXAT3 has not matched the impedance of the antenna system. This would be the case, for example, is the KXAT3 was set in bypass mode.
>> It is not on bypass mode.
>
> Just check one more thing: in order to initiate a tuning cycle, you need to push the "ATU TUNE" button, not hold the XMIT/TUNE button. If the tuning cycle is successful, you should see an indication "1.0-1" come up on the screen. Is this what you saw?
Yes I tuned pushing ATU TUNE and not holding the XMIT/TUNE. After I tuned and read 1.0-1 I saw the VSWR graph on the KX3 indicating that there was still SWR so I held TUNE to see what the reading was.
>
>>> If the SWR graph in your KX3 is set to read VSWR, and the KXAT3 has matched the antenna ad reported a VSWR of 1.0, and you see the SWR graph jumping around during transmit, then this could indicate flashover in the KXAT3. Normally this should only happen if the antenna system is very far away from 50 ohms. This is not likely to be the case here, if you indeed measured the VSWR of the antenna system independently with the MFJ antenna analyser, and found it only to be 1.4:1.
>>
>> This seems to be the case. So is it normal or not? Any idea how to fix it?
>
> No, this is not normal. If you are quite sure that you have followed the suggestions given here and the directions in the owner's manual, then the next step would be to get in touch with Elecraft customer support, who can lead you through some more detailed troubleshooting.
>
I will test again tomorrow and try on a dummy load and see if I see something weird. After that I will contact Elecraft as suggested.

Thank you
Luca
> 73, Matt VK2ACL.

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Ignacy

Re: KX3 atu anomalies - or it is me.

My ATU acted erratically. Sometimes fast tunes and sometimes nothing. Changing SWR in the middle of transmission. I asked Elecraft for replacement and it is coming.
Ignacy

Don Wilhelm-4

Re: KX3 atu anomalies - or it is me.

In reply to this post by w6ldm

Lucia,

The KX3 SWR reoports the input value to the KXAT3 that it has found
after tuning. That value may be quite different than the SWR measured
at the antenna.

If you want to check the calibration of the SWR metering in the KX3. set
the ATU MD menu parameter to BYPass and do a TUNE.
OTOH, if the ATU MD menu is set to Auto, the tuner should do a TUNE and
then report the SWR that results.

73,
Don W3FPR

On 9/19/2012 12:23 AM, luca de marinis wrote:

> Hi Don, yes I agree with you that if I measure the swr between the radio and the antenna I will have the same value I measured with the antenna analyzer.
>
> The Automatic Tuner is installed and the mane ATU MD on AUTO
>
> My point is:
>
> Why do I read ON THE KX3 swr GRAPH a peak value close to 2.0 when I transmit?
>
> Why do I read the real SWR of the antenna - in my case 1.4 - when I hold XMIT to activate TUNE?
>
> Thanks
>
> Luca
>
>
>
>
>
>
>
>
> On Sep 18, 2012, at 7:12 PM, Don Wilhelm <[hidden email]> wrote:
>
>> Lucia,
>>
>> You say that you had an SWR of 1.4, then used the ATU which lowered the
>> SWR to 1.0
>> OK, That was on the KX3 display.
>>
>> Please tell us where you were reading the continued 1.4 SWR. The KX3
>> display does not show the SWR during transmit - only during a TUNE.
>> The SWR shown externally to the KX2 ATU will not change, so if you are
>> using an external device, you will not see any change in the SWR reading.
>>
>> The KX3 ATU will reduce the SWR between the KX3 output PA and the input
>> to the KXATU3 to the value shown during on the KX3 display during a
>> TUNE, but the SWR between the KXATU3 and the antenna (as measured by an
>> external device) will not change.
>>
>> 73,
>> Don W3FPR
>>
>> On 9/18/2012 8:14 PM, luca de marinis wrote:
>>> Hi,
>>>
>>> I completed my KX3 #1715 few days ago and today I went to the park and using a Buddipole I tried to make some contacts. Buddipole swr was 1.4 on 20m so I used the ATU. It worked fine lowered the swr to 1.0 but then I transmitted I still could read a 1.4 swr. I moved up and down the band and tuned again and every time the ATU started from 9.9 and did the all cycle. Sometime couldn't go lower than 1.4. Sometimes after tuning the power was reduced to 2W
>>>
>>> Am I missing something. I did a search on the reflector but didn't show anything.
>>>
>>> Thank you in advance for your help
>>>
>>>
>> ______________________________________________________________
>> 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
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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>

NU7B

Re: KX3 atu anomalies - or it is me.

In reply to this post by w6ldm

I can report that I see the same symptoms as Luca does, on my KX3 #1690 with latest FW V1.12 and KXAT3. When I use the "Tune" button on my antenna for, say, 30 meters, I get a VSWR readout from the display of 1.3:1. Then I engage the internal ATU to bring that to 1:1. At that point, if I put the TX back in Tune mode to send a carrier - the display shows the same VSWR as it did before the ATU was exercised.

ATU mode is set to Auto. All measurements read from the KX3 display.

Steve NU7B

w6ldm

Re: KX3 atu anomalies - or it is me.

Thank you Steve, that doesn's make happy but at least I don't feel like an alien.

Luca
W6LDM

On Sep 19, 2012, at 7:38 PM, NU7B <[hidden email]> wrote:

> I can report that I see the same symptoms as Luca does, on my KX3 #1690 with
> latest FW V1.12 and KXAT3. When I use the "Tune" button on my antenna for,
> say, 30 meters, I get a VSWR readout from the display of 1.3:1. Then I
> engage the internal ATU to bring that to 1:1. At that point, if I put the TX
> back in Tune mode to send a carrier - the display shows the same VSWR as it
> did before the ATU was exercised.
>
> ATU mode is set to Auto. All measurements read from the KX3 display.
>
> Steve NU7B
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KX3-atu-anomalies-or-it-is-me-tp7562944p7563005.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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Mike WA8BXN

Re: KX3 atu anomalies - or it is me.

In reply to this post by NU7B

I use an LDG tuner at a remote location from my rig. I see something similar
to what is being discussed at times. Sometimes it will stop tuning (perhaps
quickly) when it gets a match slightly below 2:1. Other times I get a much
better match. The reason I assume is the algorithm used in the tuner. An SWR
ratio of 2:1 is not bad at all. The difference between 1.3 and 1:1 really is
not worth talking about. Part of the situation is an optimization in the
tuner algorithm. Some tuner programmers assume you would prefer a quick tune
to something below 2:1 rather than waiting a few seconds more for what may
or may not be a better match.

73 - Mike WA8BXN

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

From: NU7B
Date: 9/19/2012 10:46:23 PM
To: [hidden email]
Subject: Re: [Elecraft] KX3 atu anomalies - or it is me.

I can report that I see the same symptoms as Luca does, on my KX3 #1690 with

latest FW V1.12 and KXAT3. When I use the "Tune" button on my antenna for,
say, 30 meters, I get a VSWR readout from the display of 1.3:1. Then I
engage the internal ATU to bring that to 1:1. At that point, if I put the TX

back in Tune mode to send a carrier - the display shows the same VSWR as it
did before the ATU was exercised.

ATU mode is set to Auto. All measurements read from the KX3 display.

Steve NU7B

--
View this message in context: http://elecraft.365791.n2.nabble
com/KX3-atu-anomalies-or-it-is-me-tp7562944p7563005.html
Sent from the Elecraft mailing list archive at Nabble.com.
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NU7B

Re: KX3 atu anomalies - or it is me.

This post was updated on .

Hi Mike:

What you are describing is not what I am describing, and this thread has taken a few tangents from a central observation. Yes, the same ATU can converge to different solutions because of algorithms and starting points. Yes, it is important to be precise about what your reference point is when measuring VSWR.

The precise observation I have, which seems to mirror Luca's reply to a question from a VK-land user, is that I can measure a VSWR with Tune, then perform Autotune, and then send a carrier with Tune again, and see that the VSWR is unchanged from what it was before the tuning (Even though the ATU tune reported a lower VSWR). And I have seen that at somewhat higher than 1.3. (Agreed that 1.3 is not a big deal).

NU7B

Re: KX3 atu anomalies - or it is me.

So...

I think I have an explanation for what I am seeing. My antenna is a off-center fed stealth random wire suspended from a tree near the QTH. I feed it via 10 feet of ladder line connected to an SGC130 remote autotuner, fed by 100 feet of coax into the house. Of course the antenna is the right place to have a tuner in this situation.

The SGC gets the VSWR usually below 2:1 - but close to 2:1 on 12 meters. This is not a big deal, but the KX3 PA tended to go into high current at just over 5W with that impedance, so I use the internal ATU to give the PA a better match.

This means that I wasn't able to test the "KXAT3 ATU doesn't change things" hypothesis on a VSWR much less than 1.7:1, because the remote SGC would always bring it in at least that close.

Just now I tried the ATU on 6 meters, which the SGC does not cover and apparently can't detect, since the load remained steady at 2.9:1 during a tune carrier. When I engaged the KXAT3, it gave me a 1.5:1 solution, and a subsequent tune carrier read close to that value. So the ATU is tuning the match to the PA. I engaged the ATU again and it got to 1.1:1, and the next Tune carrier reported 1.2:1. This is entirely normal behavior for an ATU - different starting points will often find a different terminal solution. As for the deviation between SWR reported by the Tune vs the ATU - I have seen bias in other wattmeters in the reading at one forward power level vs that at a higher power level. So I don't take a difference of 0.2-0.3 in reported SWR to be abnormal.

All measurements made off of the KX3 display. I thought I was seeing an issue, but I think it is now explained.

Terry Schieler-2

Re: KX3 atu anomalies - or it is me.

In reply to this post by Mike WA8BXN

I have experienced exactly what Mike has described below. I found that auto tuners in my old Kenwood TS850-S/AT, my LDG, my K3 and others seem to get to a "reasonable" match then stop. In most every case a second press of the tuner button would, in just a few milliseconds, give a totally flat reading. My SGC-230 reacts the same way. If you are insistent on a flat SWR reading, try a second "press".

73,

Terry, WØFM

-----Original Message-----
From: Mike WA8BXN [mailto:[hidden email]]
Sent: Wednesday, September 19, 2012 10:21 PM
To: [hidden email]; NU7B
Subject: Re: [Elecraft] KX3 atu anomalies - or it is me.

I use an LDG tuner at a remote location from my rig. I see something similar to what is being discussed at times. Sometimes it will stop tuning (perhaps
quickly) when it gets a match slightly below 2:1. Other times I get a much better match. The reason I assume is the algorithm used in the tuner. An SWR ratio of 2:1 is not bad at all. The difference between 1.3 and 1:1 really is not worth talking about. Part of the situation is an optimization in the tuner algorithm. Some tuner programmers assume you would prefer a quick tune to something below 2:1 rather than waiting a few seconds more for what may or may not be a better match.

73 - Mike WA8BXN

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Phil Salas

Re: KX3 atu anomalies - or it is me.

In reply to this post by Mike WA8BXN

“...I use an LDG tuner at a remote location from my rig. I see something similar to what is being discussed at times. Sometimes it will stop tuning (perhaps quickly) when it gets a match slightly below 2:1. Other times I get a much better match...”

Don’t forget that unless your transmission system out to the remote tuner is perfect, you will see a composite SWR that could be better or worse than the remote tuned SWR (and Murphy says it will be worse!). To determine the SWR range you can see, terminate your transmission system at the remote tuner input with a good load and record the SWR. Lets call this SWRa. Most autotuners stop tuning when the SWR is at or below below 1.5:1. So now, depending on the relative phases of the mismatched systems, your SWR range measured in the shack can be:

Max SWR = SWRa X 1.5
Min SWR = SWRa/1.5 or 1.5/SWRa (whichever gives you the larger numerator).

So as an example, let’s say your terminated transmission system has an SWR of 1.3:1 on a given frequency. This could easily be the case (or worse) assuming you have switches, jumper cables, etc in-line. Then if you assume the autotuner tunes to an SWR of 1.5:1, the maximum SWR you could see in the shack could be 1.95:1, and the minimum SWR you could see would be 1.15:1.

So when you do a remote re-tune, the phase of the reflected signal as well as the tuned SWR could both be different resulting in very different in-shack SWR readings. So you really can’t always blame the remote tuner for not seeing a good in-shack SWR unless your transmission system is very good.

Phil – AD5X

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wayne burdick

Re: KX3 atu anomalies - or it is me.

Administrator

In reply to this post by w6ldm

This is most likely a firmware bug, and now on my list (thanks).
However, the difference between 1:1 and 1.3:1 is completely irrelevant
on air. So the workaround for now is: relax, and keep bugging me to
fix it one in awhile :)

73,
Wayne
N6KR

On Sep 19, 2012, at 7:44 PM, Surfshot wrote:

> Thank you Steve, that doesn's make happy but at least I don't feel
> like an alien.
>
> Luca
> W6LDM
>
> On Sep 19, 2012, at 7:38 PM, NU7B <[hidden email]> wrote:
>
>> I can report that I see the same symptoms as Luca does, on my KX3
>> #1690 with
>> latest FW V1.12 and KXAT3. When I use the "Tune" button on my
>> antenna for,
>> say, 30 meters, I get a VSWR readout from the display of 1.3:1.
>> Then I
>> engage the internal ATU to bring that to 1:1. At that point, if I
>> put the TX
>> back in Tune mode to send a carrier - the display shows the same
>> VSWR as it
>> did before the ATU was exercised.
>>
>> ATU mode is set to Auto. All measurements read from the KX3 display.
>>
>> Steve NU7B
>>
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.nabble.com/KX3-atu-anomalies-or-it-is-me-tp7562944p7563005.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> 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
> ______________________________________________________________
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