Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Peter W2IRT
Many here suggested that it was most likely a feedline issue, and I figured
this was indeed a distinct possibility.

So this afternoon I replaced the feedline. I now have about 80 feet of brand
new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at the balun
since I don't have any type-N connectors here). The AA-230 ZOOM analyzer
shows about 1.2:1 at 50.313, with resonance just below the band. I'll fix
that tomorrow, but 1.2 or 1.3:1 should be nothing to the KPA.

The TDR screen looks very clean, just a tiny bump where the feedline goes
through the (new) bulkhead connector to get into the house. See:
https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl=0

The SWR chart between 50.000 and 50.500:
https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl=0

Again, I know the antenna is resonant a bit low, but this should NOT be a
factor. So here's what's now going on.

1) Into a Cantenna dummy load, with 25W of drive from the M3s, the KPA-1500
is delivering 1075W and showing 1.4:1. No problem delivering power and no
faults.

2) With input power increased, 35W of K3s drive gives 1375W at 1.5 into the
Cantenna. Again, no problem delivering power to the purely resistive load.
Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20 second
periods without issue.

3) When I switch over to the live antenna, with25 Watts of drive from the
K3s into the actual antenna and the amp faults out instantly in bypass. When
the amplifier is in bypass and the tuner is in bypass, and when the K3s is
delivering about 90W in FT8 mode, the front panel on the KPA-1500 says the
SWR is 1.9:1. When I press the TUNE button on the radio, it's showing an SWR
of 1.4:1.

4) Amp in bypass, tuner inline, press TUNE button on the K3s and the front
panel of the KPA-1500 is showing a perfect 1.0:1 match. It SHOULD work fine
like this, right?

5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA tuner
in and untouched since step 4), the amp SOMETIMES delivers power, sometimes
faults out, shows an SWR of 1.7:1. Pressing the OPER/STBY button again to
use only exciter power, and touching NOTHING ELSE, it's back to 1.1:1 with
90W of K3s drive.

6) There is basically no rhyme or reason why this is happening and it's
*somewhat* repeatable. The incredibly frustrating part is if I see a needed
station come up, I'll flick the amp's tuner in line and it says it's tuned.
Once WSJT-X keys the radio, 90 out of 100 times the amp will hard-fault. If
it doesn't fault on the first transmission, it absolutely WILL on the second
transmission.

So I'm now at a complete loss to understand what's going on here. Amp is
fine into a resistive load. Brand-new antenna, brand new LMR-400 feedline,
brand new connectors, the KPA-1500 is faulting out the same as it did on the
10+ year old 6M5 with a patchwork of feedlines. I can't see how this is
anything but a problem in the KPA-1500 (S/N 0398).

 - pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Jim Brown
Sent: Sunday, May 31, 2020 8:22 PM
To: [hidden email]
Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues

On 5/31/2020 9:54 AM, Jim Miller wrote:
> Have you vetted your feedline at 1500w? Many times something might be
> good at low power and fail at 1500.

This is good advice. Guys who do lots of portable setup say to always check
the coax first, which mostly means check for a connector that's bad or badly
installed.

In general, if it doesn't say Amphenol or isn't stamped with a MIL spec
number, it's very likely to be poor quality. This includes barrels,
adapters, etc.  Also make sure that every connector is" wrench tight."

The advice to run it straight to a dummy load is right on -- if you have one
big enough. :)

73, Jim K9YC
______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Lovin' my K3S (S/N 10023)
73, Peter W2IRT
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Elecraft mailing list
Balun? Is it new? What kind?
You have pretty much eliminated the KPA1500 with this test. This sounds like a balun toroid heating up and causing problems.
You will see perfect conditions at low power, and the AA230 will also show things in great shape. They are not stressing the system. But 1500 watts sure will.
Talk a better look at the antenna system. And the balun. Open it up if possible.

And, again describe, in detail the antenna system. There is something there to be found.

73!
Jack, W6FB


> On May 31, 2020, at 6:29 PM, Peter Dougherty <[hidden email]> wrote:
>
> Many here suggested that it was most likely a feedline issue, and I figured
> this was indeed a distinct possibility.
>
> So this afternoon I replaced the feedline. I now have about 80 feet of brand
> new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at the balun
> since I don't have any type-N connectors here). The AA-230 ZOOM analyzer
> shows about 1.2:1 at 50.313, with resonance just below the band. I'll fix
> that tomorrow, but 1.2 or 1.3:1 should be nothing to the KPA.
>
> The TDR screen looks very clean, just a tiny bump where the feedline goes
> through the (new) bulkhead connector to get into the house. See:
> https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl=0
>
> The SWR chart between 50.000 and 50.500:
> https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl=0
>
> Again, I know the antenna is resonant a bit low, but this should NOT be a
> factor. So here's what's now going on.
>
> 1) Into a Cantenna dummy load, with 25W of drive from the M3s, the KPA-1500
> is delivering 1075W and showing 1.4:1. No problem delivering power and no
> faults.
>
> 2) With input power increased, 35W of K3s drive gives 1375W at 1.5 into the
> Cantenna. Again, no problem delivering power to the purely resistive load.
> Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20 second
> periods without issue.
>
> 3) When I switch over to the live antenna, with25 Watts of drive from the
> K3s into the actual antenna and the amp faults out instantly in bypass. When
> the amplifier is in bypass and the tuner is in bypass, and when the K3s is
> delivering about 90W in FT8 mode, the front panel on the KPA-1500 says the
> SWR is 1.9:1. When I press the TUNE button on the radio, it's showing an SWR
> of 1.4:1.
>
> 4) Amp in bypass, tuner inline, press TUNE button on the K3s and the front
> panel of the KPA-1500 is showing a perfect 1.0:1 match. It SHOULD work fine
> like this, right?
>
> 5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA tuner
> in and untouched since step 4), the amp SOMETIMES delivers power, sometimes
> faults out, shows an SWR of 1.7:1. Pressing the OPER/STBY button again to
> use only exciter power, and touching NOTHING ELSE, it's back to 1.1:1 with
> 90W of K3s drive.
>
> 6) There is basically no rhyme or reason why this is happening and it's
> *somewhat* repeatable. The incredibly frustrating part is if I see a needed
> station come up, I'll flick the amp's tuner in line and it says it's tuned.
> Once WSJT-X keys the radio, 90 out of 100 times the amp will hard-fault. If
> it doesn't fault on the first transmission, it absolutely WILL on the second
> transmission.
>
> So I'm now at a complete loss to understand what's going on here. Amp is
> fine into a resistive load. Brand-new antenna, brand new LMR-400 feedline,
> brand new connectors, the KPA-1500 is faulting out the same as it did on the
> 10+ year old 6M5 with a patchwork of feedlines. I can't see how this is
> anything but a problem in the KPA-1500 (S/N 0398).
>
> - pjd
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On
> Behalf Of Jim Brown
> Sent: Sunday, May 31, 2020 8:22 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues
>
> On 5/31/2020 9:54 AM, Jim Miller wrote:
>> Have you vetted your feedline at 1500w? Many times something might be
>> good at low power and fail at 1500.
>
> This is good advice. Guys who do lots of portable setup say to always check
> the coax first, which mostly means check for a connector that's bad or badly
> installed.
>
> In general, if it doesn't say Amphenol or isn't stamped with a MIL spec
> number, it's very likely to be poor quality. This includes barrels,
> adapters, etc.  Also make sure that every connector is" wrench tight."
>
> The advice to run it straight to a dummy load is right on -- if you have one
> big enough. :)
>
> 73, Jim K9YC
> ______________________________________________________________
> 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
> 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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Post: mailto:[hidden email]

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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Paul Baldock
In reply to this post by Peter W2IRT
A few things I observe on my KPA 1500:

On 6m the KPA1500 reads 1.3/1.4:1 into a perfect load.  FYI it reads
1.2:1 in to a perfect load on 10M also, but 1.0:1 on all other
bands.Elecraft have various excuses for this.

1500W its really pushing it on 6M. Way to much compression. I run
mine at 1100W out with 38W drive. as you state 90W, that's way too much drive.

As the amp warms up the output drops (on all bands), but I never
exceed 38W drive on 6M.

On FT8 I drive it to 500W out only, and the amp stays reasonably cool.

On 6M I bypass the tuner as the real antenna SWR is less than 1.5:1,
and I ignore what the KP1500 says it is.

Try the amp the way I use it and see how it goes.

Good luck

- Paul KW7Y



At 06:29 PM 5/31/2020, you wrote:

>Many here suggested that it was most likely a feedline issue, and I figured
>this was indeed a distinct possibility.
>
>So this afternoon I replaced the feedline. I now have about 80 feet of brand
>new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at the balun
>since I don't have any type-N connectors here). The AA-230 ZOOM analyzer
>shows about 1.2:1 at 50.313, with resonance just below the band. I'll fix
>that tomorrow, but 1.2 or 1.3:1 should be nothing to the KPA.
>
>The TDR screen looks very clean, just a tiny bump where the feedline goes
>through the (new) bulkhead connector to get into the house. See:
>https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl=0
>
>The SWR chart between 50.000 and 50.500:
>https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl=0
>
>Again, I know the antenna is resonant a bit low, but this should NOT be a
>factor. So here's what's now going on.
>
>1) Into a Cantenna dummy load, with 25W of drive from the M3s, the KPA-1500
>is delivering 1075W and showing 1.4:1. No problem delivering power and no
>faults.
>
>2) With input power increased, 35W of K3s drive gives 1375W at 1.5 into the
>Cantenna. Again, no problem delivering power to the purely resistive load.
>Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20 second
>periods without issue.
>
>3) When I switch over to the live antenna, with25 Watts of drive from the
>K3s into the actual antenna and the amp faults out instantly in bypass. When
>the amplifier is in bypass and the tuner is in bypass, and when the K3s is
>delivering about 90W in FT8 mode, the front panel on the KPA-1500 says the
>SWR is 1.9:1. When I press the TUNE button on the radio, it's showing an SWR
>of 1.4:1.
>
>4) Amp in bypass, tuner inline, press TUNE button on the K3s and the front
>panel of the KPA-1500 is showing a perfect 1.0:1 match. It SHOULD work fine
>like this, right?
>
>5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA tuner
>in and untouched since step 4), the amp SOMETIMES delivers power, sometimes
>faults out, shows an SWR of 1.7:1. Pressing the OPER/STBY button again to
>use only exciter power, and touching NOTHING ELSE, it's back to 1.1:1 with
>90W of K3s drive.
>
>6) There is basically no rhyme or reason why this is happening and it's
>*somewhat* repeatable. The incredibly frustrating part is if I see a needed
>station come up, I'll flick the amp's tuner in line and it says it's tuned.
>Once WSJT-X keys the radio, 90 out of 100 times the amp will hard-fault. If
>it doesn't fault on the first transmission, it absolutely WILL on the second
>transmission.
>
>So I'm now at a complete loss to understand what's going on here. Amp is
>fine into a resistive load. Brand-new antenna, brand new LMR-400 feedline,
>brand new connectors, the KPA-1500 is faulting out the same as it did on the
>10+ year old 6M5 with a patchwork of feedlines. I can't see how this is
>anything but a problem in the KPA-1500 (S/N 0398).
>
>  - pjd
>
>-----Original Message-----
>From: [hidden email] <[hidden email]> On
>Behalf Of Jim Brown
>Sent: Sunday, May 31, 2020 8:22 PM
>To: [hidden email]
>Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues
>
>On 5/31/2020 9:54 AM, Jim Miller wrote:
> > Have you vetted your feedline at 1500w? Many times something might be
> > good at low power and fail at 1500.
>
>This is good advice. Guys who do lots of portable setup say to always check
>the coax first, which mostly means check for a connector that's bad or badly
>installed.
>
>In general, if it doesn't say Amphenol or isn't stamped with a MIL spec
>number, it's very likely to be poor quality. This includes barrels,
>adapters, etc.  Also make sure that every connector is" wrench tight."
>
>The advice to run it straight to a dummy load is right on -- if you have one
>big enough. :)
>
>73, Jim K9YC
>______________________________________________________________
>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
>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
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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
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Peter W2IRT
In reply to this post by Elecraft mailing list
This is a brand-new balun from InnovAntennas, made specifically for this
antenna, received this past Thursday.

Note that exactly what I described was also occurring on my old setup, on an
antenna without a balun feed.

Basically everything from the output SO-239 on the KPA-1500 on up to the top
of the tower has been replaced with brand new everything. The fault
conditions are identical to what was happening beforehand.

 - pjd

-----Original Message-----
From: Jack Brindle <[hidden email]>
Sent: Sunday, May 31, 2020 9:38 PM
To: Peter Dougherty <[hidden email]>
Cc: [hidden email]
Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR
issues)

Balun? Is it new? What kind?
You have pretty much eliminated the KPA1500 with this test. This sounds like
a balun toroid heating up and causing problems.
You will see perfect conditions at low power, and the AA230 will also show
things in great shape. They are not stressing the system. But 1500 watts
sure will.
Talk a better look at the antenna system. And the balun. Open it up if
possible.

And, again describe, in detail the antenna system. There is something there
to be found.

73!
Jack, W6FB


> On May 31, 2020, at 6:29 PM, Peter Dougherty <[hidden email]> wrote:
>
> Many here suggested that it was most likely a feedline issue, and I
> figured this was indeed a distinct possibility.
>
> So this afternoon I replaced the feedline. I now have about 80 feet of
> brand new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at
> the balun since I don't have any type-N connectors here). The AA-230
> ZOOM analyzer shows about 1.2:1 at 50.313, with resonance just below
> the band. I'll fix that tomorrow, but 1.2 or 1.3:1 should be nothing to
the KPA.

>
> The TDR screen looks very clean, just a tiny bump where the feedline
> goes through the (new) bulkhead connector to get into the house. See:
> https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl
> =0
>
> The SWR chart between 50.000 and 50.500:
> https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl
> =0
>
> Again, I know the antenna is resonant a bit low, but this should NOT
> be a factor. So here's what's now going on.
>
> 1) Into a Cantenna dummy load, with 25W of drive from the M3s, the
> KPA-1500 is delivering 1075W and showing 1.4:1. No problem delivering
> power and no faults.
>
> 2) With input power increased, 35W of K3s drive gives 1375W at 1.5
> into the Cantenna. Again, no problem delivering power to the purely
resistive load.

> Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20
> second periods without issue.
>
> 3) When I switch over to the live antenna, with25 Watts of drive from
> the K3s into the actual antenna and the amp faults out instantly in
> bypass. When the amplifier is in bypass and the tuner is in bypass,
> and when the K3s is delivering about 90W in FT8 mode, the front panel
> on the KPA-1500 says the SWR is 1.9:1. When I press the TUNE button on
> the radio, it's showing an SWR of 1.4:1.
>
> 4) Amp in bypass, tuner inline, press TUNE button on the K3s and the
> front panel of the KPA-1500 is showing a perfect 1.0:1 match. It
> SHOULD work fine like this, right?
>
> 5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA
> tuner in and untouched since step 4), the amp SOMETIMES delivers
> power, sometimes faults out, shows an SWR of 1.7:1. Pressing the
> OPER/STBY button again to use only exciter power, and touching NOTHING
> ELSE, it's back to 1.1:1 with 90W of K3s drive.
>
> 6) There is basically no rhyme or reason why this is happening and
> it's
> *somewhat* repeatable. The incredibly frustrating part is if I see a
> needed station come up, I'll flick the amp's tuner in line and it says
it's tuned.

> Once WSJT-X keys the radio, 90 out of 100 times the amp will
> hard-fault. If it doesn't fault on the first transmission, it
> absolutely WILL on the second transmission.
>
> So I'm now at a complete loss to understand what's going on here. Amp
> is fine into a resistive load. Brand-new antenna, brand new LMR-400
> feedline, brand new connectors, the KPA-1500 is faulting out the same
> as it did on the
> 10+ year old 6M5 with a patchwork of feedlines. I can't see how this
> 10+ is
> anything but a problem in the KPA-1500 (S/N 0398).
>
> - pjd
>
> -----Original Message-----
> From: [hidden email]
> <[hidden email]> On Behalf Of Jim Brown
> Sent: Sunday, May 31, 2020 8:22 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues
>
> On 5/31/2020 9:54 AM, Jim Miller wrote:
>> Have you vetted your feedline at 1500w? Many times something might be
>> good at low power and fail at 1500.
>
> This is good advice. Guys who do lots of portable setup say to always
> check the coax first, which mostly means check for a connector that's
> bad or badly installed.
>
> In general, if it doesn't say Amphenol or isn't stamped with a MIL
> spec number, it's very likely to be poor quality. This includes
> barrels, adapters, etc.  Also make sure that every connector is" wrench
tight."

>
> The advice to run it straight to a dummy load is right on -- if you
> have one big enough. :)
>
> 73, Jim K9YC
> ______________________________________________________________
> 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
> 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
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]
Lovin' my K3S (S/N 10023)
73, Peter W2IRT
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Peter W2IRT
In reply to this post by Paul Baldock
Paul, please re-read what I wrote. The 90W figure is with the amp IN
STANDBY! I wouldn't dream of putting more than about 35W into the KPA-1500.
I generally like to run about 1200W on 6m, but even if I turn my K3s drive
down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT OF DRIVE
from the K3s will stop these problems. If the amp is set to deliver power
it's going to fault on 6m, regardless of what the ATU is set for (bypass or
inline), and the KPA will miss-read the SWR of the antenna system.

The resistance figure is 50.8 Ohms, and the reactance is -11 according to
the AA-230. The only difference between "works reliably" and "faults out all
the time" is one is a resistive-only load, the other has a reactive
component.

 - pjd

-----Original Message-----
From: Paul Baldock <[hidden email]>
Sent: Sunday, May 31, 2020 10:06 PM
To: Peter Dougherty <[hidden email]>; [hidden email]
Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR
issues)

A few things I observe on my KPA 1500:

On 6m the KPA1500 reads 1.3/1.4:1 into a perfect load.  FYI it reads
1.2:1 in to a perfect load on 10M also, but 1.0:1 on all other
bands.Elecraft have various excuses for this.

1500W its really pushing it on 6M. Way to much compression. I run mine at
1100W out with 38W drive. as you state 90W, that's way too much drive.

As the amp warms up the output drops (on all bands), but I never exceed 38W
drive on 6M.

On FT8 I drive it to 500W out only, and the amp stays reasonably cool.

On 6M I bypass the tuner as the real antenna SWR is less than 1.5:1, and I
ignore what the KP1500 says it is.

Try the amp the way I use it and see how it goes.

Good luck

- Paul KW7Y



At 06:29 PM 5/31/2020, you wrote:
>Many here suggested that it was most likely a feedline issue, and I
>figured this was indeed a distinct possibility.
>
>So this afternoon I replaced the feedline. I now have about 80 feet of
>brand new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at
>the balun since I don't have any type-N connectors here). The AA-230
>ZOOM analyzer shows about 1.2:1 at 50.313, with resonance just below
>the band. I'll fix that tomorrow, but 1.2 or 1.3:1 should be nothing to the
KPA.

>
>The TDR screen looks very clean, just a tiny bump where the feedline
>goes through the (new) bulkhead connector to get into the house. See:
>https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl=
>0
>
>The SWR chart between 50.000 and 50.500:
>https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl=
>0
>
>Again, I know the antenna is resonant a bit low, but this should NOT be
>a factor. So here's what's now going on.
>
>1) Into a Cantenna dummy load, with 25W of drive from the M3s, the
>KPA-1500 is delivering 1075W and showing 1.4:1. No problem delivering
>power and no faults.
>
>2) With input power increased, 35W of K3s drive gives 1375W at 1.5 into
>the Cantenna. Again, no problem delivering power to the purely resistive
load.

>Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20
>second periods without issue.
>
>3) When I switch over to the live antenna, with25 Watts of drive from
>the K3s into the actual antenna and the amp faults out instantly in
>bypass. When the amplifier is in bypass and the tuner is in bypass, and
>when the K3s is delivering about 90W in FT8 mode, the front panel on
>the KPA-1500 says the SWR is 1.9:1. When I press the TUNE button on the
>radio, it's showing an SWR of 1.4:1.
>
>4) Amp in bypass, tuner inline, press TUNE button on the K3s and the
>front panel of the KPA-1500 is showing a perfect 1.0:1 match. It SHOULD
>work fine like this, right?
>
>5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA
>tuner in and untouched since step 4), the amp SOMETIMES delivers power,
>sometimes faults out, shows an SWR of 1.7:1. Pressing the OPER/STBY
>button again to use only exciter power, and touching NOTHING ELSE, it's
>back to 1.1:1 with 90W of K3s drive.
>
>6) There is basically no rhyme or reason why this is happening and it's
>*somewhat* repeatable. The incredibly frustrating part is if I see a
>needed station come up, I'll flick the amp's tuner in line and it says it's
tuned.

>Once WSJT-X keys the radio, 90 out of 100 times the amp will
>hard-fault. If it doesn't fault on the first transmission, it
>absolutely WILL on the second transmission.
>
>So I'm now at a complete loss to understand what's going on here. Amp
>is fine into a resistive load. Brand-new antenna, brand new LMR-400
>feedline, brand new connectors, the KPA-1500 is faulting out the same
>as it did on the
>10+ year old 6M5 with a patchwork of feedlines. I can't see how this is
>anything but a problem in the KPA-1500 (S/N 0398).
>
>  - pjd
>
>-----Original Message-----
>From: [hidden email]
><[hidden email]> On Behalf Of Jim Brown
>Sent: Sunday, May 31, 2020 8:22 PM
>To: [hidden email]
>Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues
>
>On 5/31/2020 9:54 AM, Jim Miller wrote:
> > Have you vetted your feedline at 1500w? Many times something might
> > be good at low power and fail at 1500.
>
>This is good advice. Guys who do lots of portable setup say to always
>check the coax first, which mostly means check for a connector that's
>bad or badly installed.
>
>In general, if it doesn't say Amphenol or isn't stamped with a MIL spec
>number, it's very likely to be poor quality. This includes barrels,
>adapters, etc.  Also make sure that every connector is" wrench tight."
>
>The advice to run it straight to a dummy load is right on -- if you
>have one big enough. :)
>
>73, Jim K9YC
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
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>
>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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>
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>[hidden email]


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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Adrian-3
To remove any doubt, a 1.5kw or close dummy load at the end of the coax
to replace antenna, would confirm the amp issue.

On 1/6/20 12:27 pm, Peter Dougherty wrote:

> Paul, please re-read what I wrote. The 90W figure is with the amp IN
> STANDBY! I wouldn't dream of putting more than about 35W into the KPA-1500.
> I generally like to run about 1200W on 6m, but even if I turn my K3s drive
> down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT OF DRIVE
> from the K3s will stop these problems. If the amp is set to deliver power
> it's going to fault on 6m, regardless of what the ATU is set for (bypass or
> inline), and the KPA will miss-read the SWR of the antenna system.
>
> The resistance figure is 50.8 Ohms, and the reactance is -11 according to
> the AA-230. The only difference between "works reliably" and "faults out all
> the time" is one is a resistive-only load, the other has a reactive
> component.
>
>   - pjd
>
> -
>
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Peter W2IRT
New coax and old coax behaved identically. HOWEVER, running into about 80 feet of old RG-213 and into the Cantenna dummy load and it doesn't fault. This is the only condition on 6m where there is no fault. Brand new coax, old coax, brand new antenna, old antenna, with balun, without balun. Always faults except when feeding the pure resistive dummy load. If there's any reactance it trips or gives false SWR info.

I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts of drive? On the regular HF bands I can use the internal tuner to take out a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..

 - pjd

-----Original Message-----
From: Adrian <[hidden email]>
Sent: Sunday, May 31, 2020 11:05 PM
To: Peter Dougherty <[hidden email]>; 'Paul Baldock' <[hidden email]>; [hidden email]
Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

To remove any doubt, a 1.5kw or close dummy load at the end of the coax to replace antenna, would confirm the amp issue.

On 1/6/20 12:27 pm, Peter Dougherty wrote:

> Paul, please re-read what I wrote. The 90W figure is with the amp IN
> STANDBY! I wouldn't dream of putting more than about 35W into the KPA-1500.
> I generally like to run about 1200W on 6m, but even if I turn my K3s
> drive down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT
> OF DRIVE from the K3s will stop these problems. If the amp is set to
> deliver power it's going to fault on 6m, regardless of what the ATU is
> set for (bypass or inline), and the KPA will miss-read the SWR of the antenna system.
>
> The resistance figure is 50.8 Ohms, and the reactance is -11 according
> to the AA-230. The only difference between "works reliably" and
> "faults out all the time" is one is a resistive-only load, the other
> has a reactive component.
>
>   - pjd
>
> -
>

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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Vic Rosenthal
In reply to this post by Peter W2IRT
Are you using the same output connector on the KPA1500 for the dummy load and the antenna?
Perhaps the problem is in one of the SO239s or in the KPA’s switching circuit?

Victor 4X6GP

> On 1 Jun 2020, at 4:30, Peter Dougherty <[hidden email]> wrote:
>
> Many here suggested that it was most likely a feedline issue, and I figured
> this was indeed a distinct possibility.
>
> So this afternoon I replaced the feedline. I now have about 80 feet of brand
> new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at the balun
> since I don't have any type-N connectors here). The AA-230 ZOOM analyzer
> shows about 1.2:1 at 50.313, with resonance just below the band. I'll fix
> that tomorrow, but 1.2 or 1.3:1 should be nothing to the KPA.
>
> The TDR screen looks very clean, just a tiny bump where the feedline goes
> through the (new) bulkhead connector to get into the house. See:
> https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl=0
>
> The SWR chart between 50.000 and 50.500:
> https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl=0
>
> Again, I know the antenna is resonant a bit low, but this should NOT be a
> factor. So here's what's now going on.
>
> 1) Into a Cantenna dummy load, with 25W of drive from the M3s, the KPA-1500
> is delivering 1075W and showing 1.4:1. No problem delivering power and no
> faults.
>
> 2) With input power increased, 35W of K3s drive gives 1375W at 1.5 into the
> Cantenna. Again, no problem delivering power to the purely resistive load.
> Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20 second
> periods without issue.
>
> 3) When I switch over to the live antenna, with25 Watts of drive from the
> K3s into the actual antenna and the amp faults out instantly in bypass. When
> the amplifier is in bypass and the tuner is in bypass, and when the K3s is
> delivering about 90W in FT8 mode, the front panel on the KPA-1500 says the
> SWR is 1.9:1. When I press the TUNE button on the radio, it's showing an SWR
> of 1.4:1.
>
> 4) Amp in bypass, tuner inline, press TUNE button on the K3s and the front
> panel of the KPA-1500 is showing a perfect 1.0:1 match. It SHOULD work fine
> like this, right?
>
> 5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA tuner
> in and untouched since step 4), the amp SOMETIMES delivers power, sometimes
> faults out, shows an SWR of 1.7:1. Pressing the OPER/STBY button again to
> use only exciter power, and touching NOTHING ELSE, it's back to 1.1:1 with
> 90W of K3s drive.
>
> 6) There is basically no rhyme or reason why this is happening and it's
> *somewhat* repeatable. The incredibly frustrating part is if I see a needed
> station come up, I'll flick the amp's tuner in line and it says it's tuned.
> Once WSJT-X keys the radio, 90 out of 100 times the amp will hard-fault. If
> it doesn't fault on the first transmission, it absolutely WILL on the second
> transmission.
>
> So I'm now at a complete loss to understand what's going on here. Amp is
> fine into a resistive load. Brand-new antenna, brand new LMR-400 feedline,
> brand new connectors, the KPA-1500 is faulting out the same as it did on the
> 10+ year old 6M5 with a patchwork of feedlines. I can't see how this is
> anything but a problem in the KPA-1500 (S/N 0398).
>
> - pjd
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On
> Behalf Of Jim Brown
> Sent: Sunday, May 31, 2020 8:22 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues
>
>> On 5/31/2020 9:54 AM, Jim Miller wrote:
>> Have you vetted your feedline at 1500w? Many times something might be
>> good at low power and fail at 1500.
>
> This is good advice. Guys who do lots of portable setup say to always check
> the coax first, which mostly means check for a connector that's bad or badly
> installed.
>
> In general, if it doesn't say Amphenol or isn't stamped with a MIL spec
> number, it's very likely to be poor quality. This includes barrels,
> adapters, etc.  Also make sure that every connector is" wrench tight."
>
> The advice to run it straight to a dummy load is right on -- if you have one
> big enough. :)
>
> 73, Jim K9YC
> ______________________________________________________________
> 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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> 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]
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Mark Goldberg
In reply to this post by Peter W2IRT
I haven't seen a discussion of your grounding system or feedline length. 6M
can be picky.  What does your ground system look like? Do you have any
common mode chokes on the feedline? Have you tried adding or subtracting
2-3 feet from the feedline? If it is exactly a multiple of 1/2 wave or 1/4
wave changing the feedline length will move it away from that. Have you
tried adding a counterpoise in the shack? That's not the ultimate solution
but if it improves things it will tell you something. Can you point an IR
thermometer at tuner / balun inductors to see if they are getting hot? Just
throwing out ideas.

73,

Mark
W7MLG


On Sun, May 31, 2020 at 9:08 PM Peter Dougherty <[hidden email]> wrote:

> New coax and old coax behaved identically. HOWEVER, running into about 80
> feet of old RG-213 and into the Cantenna dummy load and it doesn't fault.
> This is the only condition on 6m where there is no fault. Brand new coax,
> old coax, brand new antenna, old antenna, with balun, without balun. Always
> faults except when feeding the pure resistive dummy load. If there's any
> reactance it trips or gives false SWR info.
>
> I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts
> of drive? On the regular HF bands I can use the internal tuner to take out
> a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..
>
>  - pjd
>
>
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Lou W0FK
In reply to this post by Vic Rosenthal
What are the error codes when you hard fault? Check them and see if there’s
any consistency.

 I sometimes get hard faults when I’ve moved my rf deck, simply because the
PowerPoles on the 12v line from the power supply have moved a bit and aren’t
making a good connection. I usually see a 50v warning pop up that alerts me
to the issue.  Have you made sure that 12v line is secured?

I also concur that 90 watts Drive into the amp is way too much. That
suggests the amp is the culprit. The innovantenna balun is pretty robust.
But if you suspect it, bypass it and test a direct line with pigtailed ends
directly into the loop.

73, Lou W0FK





--
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Wes Stewart-2
In reply to this post by Paul Baldock
In an earlier message on a different, but related thread:
http://elecraft.365791.n2.nabble.com/K3-SWR-Numerical-Indication-td7643839.html

I wrote:

"I would be surprised if two garden variety instruments, even placed at the same
point, would agree. The directional bridges/couplers in most "(V)SWR" meters
that hams routinely use externally or which are built into our radios are not
precision instruments.  There are a number of error sources in reflection
measurements; source match, diode non-linearity, coupler tracking errors and
often the most significant, directivity error.

In an ideal coupler, (i.e signal separation device) one port measures the
forward (incident signal) and another measures the reverse (reflected) signal
and there is no coupling between ports in the unwanted direction(s).  In other
words there is no signal at the reverse port due to the forward signal.  In a
real world coupler there is some leakage signal appearing at the reverse port
due to the forward signal, absent any reflected signal.  The "goodness" of a
directional coupler in this instance is called "directivity" and the error
signal is directivity error. Directivity is usually specified in dB.  Really
good couplers might have directivities in the 40 dB neighborhood. Really really
good directional bridges can be 50 dB, but so-so units might be 25-30 dB.  Not
ready for prime time units are lower than this.

Now I have no way of knowing what the directivities are of the couplers built
into K3s, KPA500s, KAT500s, etc. but considering that they have to work over
about 5 octaves, I'm going out on a limb and saying that 25 to 30 dB is a fair
estimate.  If I'm wrong, I'm sure I'll hear about it.  For sake of discussion
I'm going to use 26.5 dB.  What this means is that if I terminate the output
spigot of one of these radios with a perfect 50+j0 load, I'm going to measure a
leakage signal (directivity error) that is 26.5 dB below the incident value.
I'll introduce the concept of return loss here.

We hams usually speak in terms of SWR.  SWR = (1 + p) / (1 - p) where p is the
reflection coefficient. Here the p = the voltage measured at the reflected port
and the constant 1 represents the incident signal.  In reality both of these
quantities are complex numbers, they have both magnitude and phase but SWR
measurements are scalar, we throw away the phase (since it's difficult to
measure) and just use the magnitude. (In fact the symbol "p", which is really
the Greek letter rho, indicates the magnitude of the reflection coefficient in
normal usage)  We can also express this ratio as return loss, which is -20 *
log10(p).  So return loss, SWR and reflection coefficient are just different
ways to express the same thing; the ratio of incident to reflected signal.

Let's return to our example; the coupler with 26.5 dB directivity, which
indicates a return loss (RL) of 26.5 dB even with a perfect termination.  Doing
the math and converting RL = 26.5 dB to SWR we get 1.1:1.  Our perfect load
measures 1.1:1 with our imperfect instrument.  And this assumes that there are
no other errors, which there always are. But it gets worse.

Let's say that the load we want to measure really is 1.1:1.  We now have two
(apparent) reflections, 1) the real one and 2) the directivity error and they
both have the same magnitude.  In our simple detector, they sum together.  Now I
said earlier that we don't measure phase, only magnitude, but just because we
don't, or can't measure the relative phases doesn't mean they aren't there. We
will examine two cases to determine the limits of error.  Case 1) both
reflections are in phase, they add up to p + p or 2p, RL = 20.5 and SWR
~1.21:1.  Case 2) they are exactly out of phase, they sum to zero.  p = 0, RL is
infinite and SWR = 1:1.  The possible RL error is then -6 to +infinity dB!

In other words, an actual SWR of 1.1:1 can be measured anywhere between 1.0:1
and 1.2:1.  Is it any wonder that we often read about concerns that one device
measures one thing, while another located at the same, or close location
measures something different.  Of course all of this is predicated on a
directional coupler with 26.5 dB directivity and no other error sources.  It's
entirely possible that the Elecraft couplers are better than this.  They are
certainly no better than 40 dB since the internal reference resistors are 51
instead of 50 ohm.  Plus the "Tandem Match" configuration is in itself not a
great match to the transmitter output.(1)  Furthermore, the coupler, at least in
a K3 is driven by a LPF, which isn't a great 50 ohm source. Plus the coupler
output port isn't connected directly to the coax connector..... and so on and so
forth (2).  All of this creates "uncertainty."

In a metrology lab heroic efforts are made to reduce uncertainty but do we, or
should we, really care in this situation?  In my opinion, no, but everyone is
free to differ.

Wes  N7WS

(1)  See "An HF In-Line Return Loss And Power Meter" by Paul Kiciak, N2PK.
http://n2pk.com/#TP3

(2)  See "Gauge the Accuracy of SNA Measurements"
http://www.testmart.com/webdata/appnote/763.PDF"



On 5/31/2020 7:06 PM, Paul Baldock wrote:
> A few things I observe on my KPA 1500:
>
> On 6m the KPA1500 reads 1.3/1.4:1 into a perfect load.  FYI it reads 1.2:1 in
> to a perfect load on 10M also, but 1.0:1 on all other bands.Elecraft have
> various excuses for this.

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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Eric Norris-2
In reply to this post by Peter W2IRT
Is there any chance RF is getting in to the KPA1500 via an alternative
route, like one of your HF antennas, a faulty switch, loose bonding/ground,
or even a change in house wiring or wifi router, antenna rotator cable,
picking up the RF and radiating/routing it to the KPA1500 from the
antenna?  It's a shot in the dark, I know, but cut out everything but the
direct signal path originating from the K3, pull all the house breakers not
used, turn off everything--make only the 6m path active and see what
happens if this makes sense to you.

I feel your frustration--the same thing in reverse took out my 2m EME
station. I replaced every single thing, sent the K3 to Elecraft, the XV144
to Don...GUD LUCK OM!

VY 73 Eric WD6DBM

On Sun, May 31, 2020, 9:07 PM Peter Dougherty <[hidden email]> wrote:

> New coax and old coax behaved identically. HOWEVER, running into about 80
> feet of old RG-213 and into the Cantenna dummy load and it doesn't fault.
> This is the only condition on 6m where there is no fault. Brand new coax,
> old coax, brand new antenna, old antenna, with balun, without balun. Always
> faults except when feeding the pure resistive dummy load. If there's any
> reactance it trips or gives false SWR info.
>
> I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts
> of drive? On the regular HF bands I can use the internal tuner to take out
> a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..
>
>  - pjd
>
> -----Original Message-----
> From: Adrian <[hidden email]>
> Sent: Sunday, May 31, 2020 11:05 PM
> To: Peter Dougherty <[hidden email]>; 'Paul Baldock' <
> [hidden email]>; [hidden email]
> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR
> issues)
>
> To remove any doubt, a 1.5kw or close dummy load at the end of the coax to
> replace antenna, would confirm the amp issue.
>
> On 1/6/20 12:27 pm, Peter Dougherty wrote:
> > Paul, please re-read what I wrote. The 90W figure is with the amp IN
> > STANDBY! I wouldn't dream of putting more than about 35W into the
> KPA-1500.
> > I generally like to run about 1200W on 6m, but even if I turn my K3s
> > drive down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT
> > OF DRIVE from the K3s will stop these problems. If the amp is set to
> > deliver power it's going to fault on 6m, regardless of what the ATU is
> > set for (bypass or inline), and the KPA will miss-read the SWR of the
> antenna system.
> >
> > The resistance figure is 50.8 Ohms, and the reactance is -11 according
> > to the AA-230. The only difference between "works reliably" and
> > "faults out all the time" is one is a resistive-only load, the other
> > has a reactive component.
> >
> >   - pjd
> >
> > -
> >
>
> ______________________________________________________________
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Jim Brown-10
In reply to this post by Peter W2IRT
On 5/31/2020 7:22 PM, Peter Dougherty wrote:
> This is a brand-new balun from InnovAntennas, made specifically for this
> antenna, received this past Thursday.

The word "balun" has been used to describe nearly a dozen VERY different
physical things, and is thus totally useless as a descriptor of what you
used (or what they sold you). Buy me a case of a good single malt Scotch
and I'll run down the list.

I have extensively studied only one set of those "things," common mode
chokes formed by winding a length of transmission line onto a ferrite
core that is lossy at the frequency(ies) of interest, forming a parallel
resonance in the common mode circuit where the RESISTIVE component of
the low-Q parallel resonance is what makes the choke work.

A good common mode choke does not interact with a well-designed antenna
unless the Zo of the transmission line wound onto the ferrite core is
mismatched to the antenna. And I emphatically do NOT call them "baluns"
because use of that word obscures understanding of HOW they work.

73, Jim K9YC
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

David Olean
In reply to this post by Eric Norris-2
Hello Peter

I suspect RFI as well. I do not have a KPA1500, so my advice is not
worth much, but the fact that the fault only occurs when a signal is
being radiated sends me a red flag.  I had a similar problem here with
my SPE amplifier power output. I was measuring it on an LP-100A
wattmeter.  It turns out that 1.8 MHz energy from the SPE amp radiated
from my vertical antenna and  was getting into a new wire doublet
antenna and coming back down the ladder line into the shack. The ladder
line was about 7 inches from the power coupler for the LP-100A. RF
caused the readings to go wacky and it looked like my amplifier was
going postal!  The problem was high rf fields next to the power meter
coupler.

Ferrite balun heating can be seen with a VSWR meter if you set the power
at some intermediate level, key the amp up with a steady carrier, and
watch for VSWR creeping up.  Loose pins in coax can also be a problem.
They can heat up and disconnect or start arcing. Those problems do not
typically show VSWR creep. They happen all at once usually.

The KPA1500 works fine into a dummy load. (No RFI)  That is a big
clue.   Good luck and I hope you find the problem. Maybe an RF sniffer
would detect the ingress point?

73

Dave K1WHS


On 6/1/2020 5:24 AM, Eric Norris wrote:

> Is there any chance RF is getting in to the KPA1500 via an alternative
> route, like one of your HF antennas, a faulty switch, loose bonding/ground,
> or even a change in house wiring or wifi router, antenna rotator cable,
> picking up the RF and radiating/routing it to the KPA1500 from the
> antenna?  It's a shot in the dark, I know, but cut out everything but the
> direct signal path originating from the K3, pull all the house breakers not
> used, turn off everything--make only the 6m path active and see what
> happens if this makes sense to you.
>
> I feel your frustration--the same thing in reverse took out my 2m EME
> station. I replaced every single thing, sent the K3 to Elecraft, the XV144
> to Don...GUD LUCK OM!
>
> VY 73 Eric WD6DBM
>
> On Sun, May 31, 2020, 9:07 PM Peter Dougherty <[hidden email]> wrote:
>
>> New coax and old coax behaved identically. HOWEVER, running into about 80
>> feet of old RG-213 and into the Cantenna dummy load and it doesn't fault.
>> This is the only condition on 6m where there is no fault. Brand new coax,
>> old coax, brand new antenna, old antenna, with balun, without balun. Always
>> faults except when feeding the pure resistive dummy load. If there's any
>> reactance it trips or gives false SWR info.
>>
>> I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts
>> of drive? On the regular HF bands I can use the internal tuner to take out
>> a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..
>>
>>   - pjd
>>
>> -----Original Message-----
>> From: Adrian <[hidden email]>
>> Sent: Sunday, May 31, 2020 11:05 PM
>> To: Peter Dougherty <[hidden email]>; 'Paul Baldock' <
>> [hidden email]>; [hidden email]
>> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR
>> issues)
>>
>> To remove any doubt, a 1.5kw or close dummy load at the end of the coax to
>> replace antenna, would confirm the amp issue.
>>
>> On 1/6/20 12:27 pm, Peter Dougherty wrote:
>>> Paul, please re-read what I wrote. The 90W figure is with the amp IN
>>> STANDBY! I wouldn't dream of putting more than about 35W into the
>> KPA-1500.
>>> I generally like to run about 1200W on 6m, but even if I turn my K3s
>>> drive down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT
>>> OF DRIVE from the K3s will stop these problems. If the amp is set to
>>> deliver power it's going to fault on 6m, regardless of what the ATU is
>>> set for (bypass or inline), and the KPA will miss-read the SWR of the
>> antenna system.
>>> The resistance figure is 50.8 Ohms, and the reactance is -11 according
>>> to the AA-230. The only difference between "works reliably" and
>>> "faults out all the time" is one is a resistive-only load, the other
>>> has a reactive component.
>>>
>>>    - pjd
>>>
>>> -
>>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
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>>
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

NK7Z
In reply to this post by Peter W2IRT
Peter,

If my antenna system had 2.5 to 3 to 1 SWR, I would not run 1.5 KW.  I'd
be looking at my antenna...

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 5/31/20 9:07 PM, Peter Dougherty wrote:

> I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts of drive? On the regular HF bands I can use the internal tuner to take out a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..
>
>   - pjd
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Stephen Shearer
In reply to this post by David Olean
Ground loops can be another issue.
I was having a "feed back" issue with my KX3/KXPA100 ans solved it
eliminating ground/power loops.

73, steve WB3LGC

On 6/1/20 8:25 AM, David Olean wrote:

> Hello Peter
>
> I suspect RFI as well. I do not have a KPA1500, so my advice is not
> worth much, but the fact that the fault only occurs when a signal is
> being radiated sends me a red flag.  I had a similar problem here with
> my SPE amplifier power output. I was measuring it on an LP-100A
> wattmeter.  It turns out that 1.8 MHz energy from the SPE amp radiated
> from my vertical antenna and  was getting into a new wire doublet
> antenna and coming back down the ladder line into the shack. The ladder
> line was about 7 inches from the power coupler for the LP-100A. RF
> caused the readings to go wacky and it looked like my amplifier was
> going postal!  The problem was high rf fields next to the power meter
> coupler.
>
> Ferrite balun heating can be seen with a VSWR meter if you set the power
> at some intermediate level, key the amp up with a steady carrier, and
> watch for VSWR creeping up.  Loose pins in coax can also be a problem.
> They can heat up and disconnect or start arcing. Those problems do not
> typically show VSWR creep. They happen all at once usually.
>
> The KPA1500 works fine into a dummy load. (No RFI)  That is a big
> clue.   Good luck and I hope you find the problem. Maybe an RF sniffer
> would detect the ingress point?
>
> 73
>
> Dave K1WHS
>
>
> On 6/1/2020 5:24 AM, Eric Norris wrote:
>> Is there any chance RF is getting in to the KPA1500 via an alternative
>> route, like one of your HF antennas, a faulty switch, loose
>> bonding/ground,
>> or even a change in house wiring or wifi router, antenna rotator cable,
>> picking up the RF and radiating/routing it to the KPA1500 from the
>> antenna?  It's a shot in the dark, I know, but cut out everything but the
>> direct signal path originating from the K3, pull all the house
>> breakers not
>> used, turn off everything--make only the 6m path active and see what
>> happens if this makes sense to you.
>>
>> I feel your frustration--the same thing in reverse took out my 2m EME
>> station. I replaced every single thing, sent the K3 to Elecraft, the
>> XV144
>> to Don...GUD LUCK OM!
>>
>> VY 73 Eric WD6DBM
>>
>> On Sun, May 31, 2020, 9:07 PM Peter Dougherty <[hidden email]> wrote:
>>
>>> New coax and old coax behaved identically. HOWEVER, running into
>>> about 80
>>> feet of old RG-213 and into the Cantenna dummy load and it doesn't
>>> fault.
>>> This is the only condition on 6m where there is no fault. Brand new
>>> coax,
>>> old coax, brand new antenna, old antenna, with balun, without balun.
>>> Always
>>> faults except when feeding the pure resistive dummy load. If there's any
>>> reactance it trips or gives false SWR info.
>>>
>>> I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts
>>> of drive? On the regular HF bands I can use the internal tuner to
>>> take out
>>> a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..
>>>
>>>   - pjd
>>>
>>> -----Original Message-----
>>> From: Adrian <[hidden email]>
>>> Sent: Sunday, May 31, 2020 11:05 PM
>>> To: Peter Dougherty <[hidden email]>; 'Paul Baldock' <
>>> [hidden email]>; [hidden email]
>>> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on
>>> 6m; SWR
>>> issues)
>>>
>>> To remove any doubt, a 1.5kw or close dummy load at the end of the
>>> coax to
>>> replace antenna, would confirm the amp issue.
>>>
>>> On 1/6/20 12:27 pm, Peter Dougherty wrote:
>>>> Paul, please re-read what I wrote. The 90W figure is with the amp IN
>>>> STANDBY! I wouldn't dream of putting more than about 35W into the
>>> KPA-1500.
>>>> I generally like to run about 1200W on 6m, but even if I turn my K3s
>>>> drive down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT
>>>> OF DRIVE from the K3s will stop these problems. If the amp is set to
>>>> deliver power it's going to fault on 6m, regardless of what the ATU is
>>>> set for (bypass or inline), and the KPA will miss-read the SWR of the
>>> antenna system.
>>>> The resistance figure is 50.8 Ohms, and the reactance is -11 according
>>>> to the AA-230. The only difference between "works reliably" and
>>>> "faults out all the time" is one is a resistive-only load, the other
>>>> has a reactive component.
>>>>
>>>>    - pjd
>>>>
>>>> -
>>>>
>>> ______________________________________________________________
>>> 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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>>
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Re: NOT the feedline

Alan - G4GNX
In reply to this post by David Olean
I have a similar issue with ferrite 'balun' heating, although mostly
tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
balun at the feed point, but also has a sleeve 'balun' consisting of 8
ferrites wrapped in a plastic sleeve, about 3 feet from the feed point.
If I run the K3S at 100W, via the KPA500 in standby, then through the
KAT500 tuner, I see no problems.

On increasing the power to 200W by using the KPA500 in Operate and about
10W drive from the K3S, during a SSB 'over' the temperature of the
KPA500 rises and after a few minutes, the SWR readings on the KPA500 and
KAT500 start to rise. One of the Elecraft guys actually very kindly went
through my fault log and came to the conclusion that the fault is with
the antenna/feeder and I agree with him. What is strange is that if I
leave a solid carrier running at 200W, I can't easily reproduce the
issue and I wonder if its something being affected by peak excursions
with SSB?

When things do start to go wrong, I can usually perform a manual tune
with the KAT500 and the fault will then not (mostly) be apparent.

Anyway, I'm in the process of replacing the entire feeder with Westflex
103 and much bigger ferrites. I will also replace the main balun which
is a 400W device for a 1KW device, as I think that running the UK max of
400W may be pushing the spec of a 400W balun. Also, the balun itself or
connections to it may be faulty.

The point now is that I have discovered some damage to the outer
covering of the sleeve 'balun' which may be the result of ferrites
overheating or may be the cause of movement of the ferrites thus causing
instability. Either way, heftier devices seem to be the order of the
day.

Although the KPA500 temperature rise is somewhat expected, I feel it's a
bit higher over a short period than I would like and may be due to
reflected power.

73,

Alan. G4GNX


------ Original Message ------
From: "David Olean" <[hidden email]>
To: "Peter Dougherty" <[hidden email]>
Cc: [hidden email]
Sent: 01/06/2020 13:25:18
Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m;
SWR issues)

>Hello Peter
>
>I suspect RFI as well. I do not have a KPA1500, so my advice is not worth much, but the fact that the fault only occurs when a signal is being radiated sends me a red flag.  I had a similar problem here with my SPE amplifier power output. I was measuring it on an LP-100A wattmeter.  It turns out that 1.8 MHz energy from the SPE amp radiated from my vertical antenna and  was getting into a new wire doublet antenna and coming back down the ladder line into the shack. The ladder line was about 7 inches from the power coupler for the LP-100A. RF caused the readings to go wacky and it looked like my amplifier was going postal!  The problem was high rf fields next to the power meter coupler.
>
>Ferrite balun heating can be seen with a VSWR meter if you set the power at some intermediate level, key the amp up with a steady carrier, and watch for VSWR creeping up.  Loose pins in coax can also be a problem. They can heat up and disconnect or start arcing. Those problems do not typically show VSWR creep. They happen all at once usually.
>
>The KPA1500 works fine into a dummy load. (No RFI)  That is a big clue.   Good luck and I hope you find the problem. Maybe an RF sniffer would detect the ingress point?
>
>73
>
>Dave K1WHS
>

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Re: NOT the feedline

Adrian-3
If you use a decent combination balun such as ;
https://www.balundesigns.com/model-4116-4-1-hybrid-balun-1-5-54mhz-3kw/ 
if you have any metal structure in range of the field, or

https://www.balundesigns.com/model-4115ocf-4-1-for-ocf-dipoles-1-5-54-mhz-5kw/ 
for a total current 4:1 balun. These are very robust at high power, and
no other feedpoint RF common mode choke is required.

I ran a K3 , amp and ocf dipole like this, with above balun earlier this
decade with great success, had top 4a4a dxpedition total band vk points
with this one antenna. Also the windom and ocf are different animals.

The true windom uses the vertical section of its feedline as part of the
antenna, such that any ocf dipole with a feedpoint common mode choke
cannot be referred to as a 'windom'

Adrian Fewster


On 1/6/20 11:45 pm, Alan - G4GNX wrote:

> I have a similar issue with ferrite 'balun' heating, although mostly
> tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
> balun at the feed point, but also has a sleeve 'balun' consisting of 8
> ferrites wrapped in a plastic sleeve, about 3 feet from the feed
> point. If I run the K3S at 100W, via the KPA500 in standby, then
> through the KAT500 tuner, I see no problems.
>
> On increasing the power to 200W by using the KPA500 in Operate and
> about 10W drive from the K3S, during a SSB 'over' the temperature of
> the KPA500 rises and after a few minutes, the SWR readings on the
> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
> very kindly went through my fault log and came to the conclusion that
> the fault is with the antenna/feeder and I agree with him. What is
> strange is that if I leave a solid carrier running at 200W, I can't
> easily reproduce the issue and I wonder if its something being
> affected by peak excursions with SSB?
>
> When things do start to go wrong, I can usually perform a manual tune
> with the KAT500 and the fault will then not (mostly) be apparent.
>
> Anyway, I'm in the process of replacing the entire feeder with
> Westflex 103 and much bigger ferrites. I will also replace the main
> balun which is a 400W device for a 1KW device, as I think that running
> the UK max of 400W may be pushing the spec of a 400W balun. Also, the
> balun itself or connections to it may be faulty.
>
> The point now is that I have discovered some damage to the outer
> covering of the sleeve 'balun' which may be the result of ferrites
> overheating or may be the cause of movement of the ferrites thus
> causing instability. Either way, heftier devices seem to be the order
> of the day.
>
> Although the KPA500 temperature rise is somewhat expected, I feel it's
> a bit higher over a short period than I would like and may be due to
> reflected power.
>
> 73,
>
> Alan. G4GNX
>
>
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Peter W2IRT
In reply to this post by Vic Rosenthal
That's worth a shot. I have a ~7 foot RG-213 patch cable from the back of the amp to the entry box. I don't have any more LMR-400 so I can't use that, but I do have quite a bit of 213 and will make a new patch cable. That's the only bit of the old system that's still remaining.
 - pjd

-----Original Message-----
From: Vic Rosenthal <[hidden email]>
Sent: Monday, June 1, 2020 12:18 AM
To: Peter Dougherty <[hidden email]>
Cc: [hidden email]; [hidden email]
Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Are you using the same output connector on the KPA1500 for the dummy load and the antenna?
Perhaps the problem is in one of the SO239s or in the KPA’s switching circuit?

Victor 4X6GP

> On 1 Jun 2020, at 4:30, Peter Dougherty <[hidden email]> wrote:
>
> Many here suggested that it was most likely a feedline issue, and I
> figured this was indeed a distinct possibility.
>
> So this afternoon I replaced the feedline. I now have about 80 feet of
> brand new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at
> the balun since I don't have any type-N connectors here). The AA-230
> ZOOM analyzer shows about 1.2:1 at 50.313, with resonance just below
> the band. I'll fix that tomorrow, but 1.2 or 1.3:1 should be nothing to the KPA.
>
> The TDR screen looks very clean, just a tiny bump where the feedline
> goes through the (new) bulkhead connector to get into the house. See:
> https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl
> =0
>
> The SWR chart between 50.000 and 50.500:
> https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl
> =0
>
> Again, I know the antenna is resonant a bit low, but this should NOT
> be a factor. So here's what's now going on.
>
> 1) Into a Cantenna dummy load, with 25W of drive from the M3s, the
> KPA-1500 is delivering 1075W and showing 1.4:1. No problem delivering
> power and no faults.
>
> 2) With input power increased, 35W of K3s drive gives 1375W at 1.5
> into the Cantenna. Again, no problem delivering power to the purely resistive load.
> Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20
> second periods without issue.
>
> 3) When I switch over to the live antenna, with25 Watts of drive from
> the K3s into the actual antenna and the amp faults out instantly in
> bypass. When the amplifier is in bypass and the tuner is in bypass,
> and when the K3s is delivering about 90W in FT8 mode, the front panel
> on the KPA-1500 says the SWR is 1.9:1. When I press the TUNE button on
> the radio, it's showing an SWR of 1.4:1.
>
> 4) Amp in bypass, tuner inline, press TUNE button on the K3s and the
> front panel of the KPA-1500 is showing a perfect 1.0:1 match. It
> SHOULD work fine like this, right?
>
> 5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA
> tuner in and untouched since step 4), the amp SOMETIMES delivers
> power, sometimes faults out, shows an SWR of 1.7:1. Pressing the
> OPER/STBY button again to use only exciter power, and touching NOTHING
> ELSE, it's back to 1.1:1 with 90W of K3s drive.
>
> 6) There is basically no rhyme or reason why this is happening and
> it's
> *somewhat* repeatable. The incredibly frustrating part is if I see a
> needed station come up, I'll flick the amp's tuner in line and it says it's tuned.
> Once WSJT-X keys the radio, 90 out of 100 times the amp will
> hard-fault. If it doesn't fault on the first transmission, it
> absolutely WILL on the second transmission.
>
> So I'm now at a complete loss to understand what's going on here. Amp
> is fine into a resistive load. Brand-new antenna, brand new LMR-400
> feedline, brand new connectors, the KPA-1500 is faulting out the same
> as it did on the
> 10+ year old 6M5 with a patchwork of feedlines. I can't see how this
> 10+ is
> anything but a problem in the KPA-1500 (S/N 0398).
>
> - pjd
>
> -----Original Message-----
> From: [hidden email]
> <[hidden email]> On Behalf Of Jim Brown
> Sent: Sunday, May 31, 2020 8:22 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues
>
>> On 5/31/2020 9:54 AM, Jim Miller wrote:
>> Have you vetted your feedline at 1500w? Many times something might be
>> good at low power and fail at 1500.
>
> This is good advice. Guys who do lots of portable setup say to always
> check the coax first, which mostly means check for a connector that's
> bad or badly installed.
>
> In general, if it doesn't say Amphenol or isn't stamped with a MIL
> spec number, it's very likely to be poor quality. This includes
> barrels, adapters, etc.  Also make sure that every connector is" wrench tight."
>
> The advice to run it straight to a dummy load is right on -- if you
> have one big enough. :)
>
> 73, Jim K9YC
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Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Peter W2IRT
In reply to this post by Mark Goldberg
The new full-length LMR-400 cable is about 3 feet longer than the old 2-section coax I had before (old = 3/8” hardline and about 8 feet of RG-213). The entry point is grounded to rod immediately below it, connected by 1.5” braid.

 

- pjd

 

From: Mark Goldberg <[hidden email]>
Sent: Monday, June 1, 2020 12:45 AM
To: Peter Dougherty <[hidden email]>
Cc: Adrian <[hidden email]>; Paul Baldock <[hidden email]>; Elecraft Mailing List <[hidden email]>
Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

 

I haven't seen a discussion of your grounding system or feedline length. 6M can be picky.  What does your ground system look like? Do you have any common mode chokes on the feedline? Have you tried adding or subtracting 2-3 feet from the feedline? If it is exactly a multiple of 1/2 wave or 1/4 wave changing the feedline length will move it away from that. Have you tried adding a counterpoise in the shack? That's not the ultimate solution but if it improves things it will tell you something. Can you point an IR thermometer at tuner / balun inductors to see if they are getting hot? Just throwing out ideas.

 

73,

 

Mark

W7MLG

 

 

On Sun, May 31, 2020 at 9:08 PM Peter Dougherty <[hidden email] <mailto:[hidden email]> > wrote:

New coax and old coax behaved identically. HOWEVER, running into about 80 feet of old RG-213 and into the Cantenna dummy load and it doesn't fault. This is the only condition on 6m where there is no fault. Brand new coax, old coax, brand new antenna, old antenna, with balun, without balun. Always faults except when feeding the pure resistive dummy load. If there's any reactance it trips or gives false SWR info.

I would also add, why would a 2:1 SWR trip out the amp at 25 or 30 Watts of drive? On the regular HF bands I can use the internal tuner to take out a 2.5 or 3:1 SWR and it still sends 1400-1450 Watts up the pipe..

 - pjd
 

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