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80m KPA1500 High reflected power problems

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Peter W2IRT

80m KPA1500 High reflected power problems

HI guys,
I'm still having a serious problem on 80m with my KPA1500.

With the amp inline I'm getting high reflected power fault everywhere below
about 3675. My antenna (an inverted vee) is resonant at 3550, and the SWR is
below 2:1 from 3500 to 3630.

This was happening in the past as well, and prompted me to completely
rebuild the antenna last summer. The antenna is fed with 100' of brand new
Davis BuryFlex feedline, a brand-new 5kW-rated Balun Designs 1:1 current
balun, new 12 AWG copper-clad steel wire, even new heavy ceramic insulators!

Without the amp everything's fine. I can push 100W through to the antenna
all day; the SWR LEDs on the amp (bypassed) show two green and that's it.
It's fine on every other band, including 80/75 phone.

With the amp in, If I drop the drive to 10W or less, the amp is happy and I
get about 450 Watts out. But the instant I drive it with ~15 Watts (when the
K3s kicks the high power module in, and I hear the internal relay click, I
get the HI SWR warning and the amp faults. 100% repeatable. Doesn't matter
if the tuner is in or out..there's NO way to get high power out of the KPA
on 80 CW.

More details: If the KPA's tuner is bypassed it just faults instantly. If
the tuner is placed inline and I find a match, I can get about a second's or
two's worth of power before the SWR LEDs start lighting up, then the fault
happens.

Any idea what's going on here? This is unbelievably frustrating.

---------------------------------------------
73 and Good DX
Peter, W2IRT

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Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Don Wilhelm

Re: 80m KPA1500 High reflected power problems

Peter,

Isolate the problem to the amplifier. Get a high power dummy load if
you do not already have one. Run the amp at 1000 watts or more into the
dummy load. If the amp behaves the same as it does with the antenna,
then the problem is in the amplifier.
But if the amp behaves into the dummy load, look for marginal
connections to your antenna, PL-259 connectors not sufficiently
tightened, balun overload, arcing at either the center insulator or at
the end insulators.
There is very high RF voltage at the antenna ends, and it may be arcing
over the end insulators - don't overlook that possibility.

73,
Don W3FPR

On 3/9/2019 1:50 PM, Peter Dougherty wrote:

> HI guys,
> I'm still having a serious problem on 80m with my KPA1500.
>
> With the amp inline I'm getting high reflected power fault everywhere below
> about 3675. My antenna (an inverted vee) is resonant at 3550, and the SWR is
> below 2:1 from 3500 to 3630.
>
>
>
> This was happening in the past as well, and prompted me to completely
> rebuild the antenna last summer. The antenna is fed with 100' of brand new
> Davis BuryFlex feedline, a brand-new 5kW-rated Balun Designs 1:1 current
> balun, new 12 AWG copper-clad steel wire, even new heavy ceramic insulators!
>
>
> Without the amp everything's fine. I can push 100W through to the antenna
> all day; the SWR LEDs on the amp (bypassed) show two green and that's it.
> It's fine on every other band, including 80/75 phone.
>
>
>
> With the amp in, If I drop the drive to 10W or less, the amp is happy and I
> get about 450 Watts out. But the instant I drive it with ~15 Watts (when the
> K3s kicks the high power module in, and I hear the internal relay click, I
> get the HI SWR warning and the amp faults. 100% repeatable. Doesn't matter
> if the tuner is in or out..there's NO way to get high power out of the KPA
> on 80 CW.

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WW3S

Re: 80m KPA1500 High reflected power problems

In reply to this post by Peter W2IRT

Any cheap bulkhead connectors in the feed? I just got burnt by one on my radial plate....

Sent from my Verizon Motorola Smartphone
On Mar 9, 2019 2:04 PM, Don Wilhelm <[hidden email]> wrote:

>
> Peter,
>
> Isolate the problem to the amplifier. Get a high power dummy load if
> you do not already have one. Run the amp at 1000 watts or more into the
> dummy load. If the amp behaves the same as it does with the antenna,
> then the problem is in the amplifier.
> But if the amp behaves into the dummy load, look for marginal
> connections to your antenna, PL-259 connectors not sufficiently
> tightened, balun overload, arcing at either the center insulator or at
> the end insulators.
> There is very high RF voltage at the antenna ends, and it may be arcing
> over the end insulators - don't overlook that possibility.
>
> 73,
> Don W3FPR
>
> On 3/9/2019 1:50 PM, Peter Dougherty wrote:
> > HI guys,
> > I'm still having a serious problem on 80m with my KPA1500.
> >
> > With the amp inline I'm getting high reflected power fault everywhere below
> > about 3675. My antenna (an inverted vee) is resonant at 3550, and the SWR is
> > below 2:1 from 3500 to 3630.
> >
> >
> >
> > This was happening in the past as well, and prompted me to completely
> > rebuild the antenna last summer. The antenna is fed with 100' of brand new
> > Davis BuryFlex feedline, a brand-new 5kW-rated Balun Designs 1:1 current
> > balun, new 12 AWG copper-clad steel wire, even new heavy ceramic insulators!
> >
> >
> > Without the amp everything's fine. I can push 100W through to the antenna
> > all day; the SWR LEDs on the amp (bypassed) show two green and that's it.
> > It's fine on every other band, including 80/75 phone.
> >
> >
> >
> > With the amp in, If I drop the drive to 10W or less, the amp is happy and I
> > get about 450 Watts out. But the instant I drive it with ~15 Watts (when the
> > K3s kicks the high power module in, and I hear the internal relay click, I
> > get the HI SWR warning and the amp faults. 100% repeatable. Doesn't matter
> > if the tuner is in or out..there's NO way to get high power out of the KPA
> > on 80 CW.
> ______________________________________________________________
> 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

Grant Youngman-2

Re: 80m KPA1500 High reflected power problems

Don’t overlook any F-F connector’s in the system. The first time I hit my Hexbeam with the legal limit, the F-F connector joining my feed line to the antenna connection stub arced over. It had always been fine at low power, but was a fester find that turned out not to be a bargain. It was completely cooked. Fortunately, my SWR bridge tripped off the transmit line on high SWR. Probably at some high but lower power level it would have only sporadically arced creating a much more fun diagnosis problem.

Grant NQ5T
K3 #2091 KX3 #8342

> On Mar 9, 2019, at 2:09 PM, Jamie WW3S <[hidden email]> wrote:
>
> Any cheap bulkhead connectors in the feed? I just got burnt by one on my radial plate....
>
> Sent from my Verizon Motorola Smartphone
> On Mar 9, 2019 2:04 PM, Don Wilhelm <[hidden email]> wrote:
>>

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Peter W2IRT

Re: 80m KPA1500 High reflected power problems

In reply to this post by WW3S

All PL-259 connectors here that I assembled are Amphenol 83-SP1. Female conenctors are whatever the device came with. The only female connectors in the line are on the amp, the HF-Auto Tuner, antenna switch and the balun. The only one that's not common to all my other antennas is the balun, and Balun Designs makes top-notch products. My old balun--the one I replaced thinking it was the problem last summer--was from Array Solutions and the same problem existed there.

Connectors are all tightened 1/4 turn.

I don't presently have access to a dummy load. The feedline connecting it to the outdoor antenna switch is damaged and it's difficult to reach at the moment--across a 40' crawlspace.

The faults are all high SWR:
570 19-03-09T20:06:40 FLT 90 - PWR REFL freq 3512 inp 11W fwd 826W refl 199W swr 2.9 53A 31C adc 254 var 199
569 19-03-09T20:06:37 OVR 90 - PWR REFL inp 12W fwd 915W refl 173W swr 2.5 52A 32C adc 236 var 173
568 19-03-09T20:06:28 ON 00 - ON 1 times firmware version 02.09
567 19-03-09T18:40:56 FLT 90 - PWR REFL freq 3656 inp 10W fwd 613W refl 225W swr 4.0 21A 29C adc 271 var 225
566 19-03-09T18:37:30 OVR 90 - PWR REFL freq 3688 inp 21W fwd 881W refl 180W swr 2.6 35A 29C adc 241 var 180
565 19-03-09T18:37:06 FLT 90 - PWR REFL freq 3640 inp 8W fwd 616W refl 201W swr 3.6 26A 29C adc 255 var 201
564 19-03-09T18:36:51 FLT 90 - PWR REFL freq 3640 inp 10W fwd 676W refl 213W swr 3.5 23A 29C adc 263 var 213
563 19-03-09T18:32:09 FLT 90 - PWR REFL freq 3552 inp 7W fwd 484W refl 207W swr 4.7 10A 26C adc 259 var 207
562 19-03-09T18:31:04 FLT 90 - PWR REFL freq 3552 inp 8W fwd 499W refl 196W swr 4.3 11A 25C adc 252 var 196
561 19-03-09T18:26:19 FLT 90 - PWR REFL freq 3520 inp 4W fwd 356W refl 207W swr 7.4 12A 25C adc 259 var 207
560 19-03-09T18:25:37 FLT 90 - PWR REFL freq 3504 inp 9W fwd 637W refl 204W swr 3.6 25A 25C adc 257 var 204
559 19-03-09T18:25:03 FLT 90 - PWR REFL freq 3504 inp 17W fwd 1035W refl 204W swr 2.5 8A 25C adc 257 var 204
558 19-03-09T18:24:43 FLT 90 - PWR REFL freq 3504 inp 14W fwd 878W refl 213W swr 2.9 23A 24C adc 263 var 213

- pjd

-----Original Message-----
From: Jamie WW3S <[hidden email]>
Sent: Saturday, March 9, 2019 2:09 PM
To: [hidden email]
Cc: [hidden email]; Peter Dougherty <[hidden email]>
Subject: Re: [Elecraft] 80m KPA1500 High reflected power problems

Any cheap bulkhead connectors in the feed? I just got burnt by one on my radial plate....

Sent from my Verizon Motorola Smartphone On Mar 9, 2019 2:04 PM, Don Wilhelm <[hidden email]> wrote:

>
> Peter,
>
> Isolate the problem to the amplifier. Get a high power dummy load if
> you do not already have one. Run the amp at 1000 watts or more into
> the dummy load. If the amp behaves the same as it does with the
> antenna, then the problem is in the amplifier.
> But if the amp behaves into the dummy load, look for marginal
> connections to your antenna, PL-259 connectors not sufficiently
> tightened, balun overload, arcing at either the center insulator or at
> the end insulators.
> There is very high RF voltage at the antenna ends, and it may be
> arcing over the end insulators - don't overlook that possibility.
>
> 73,
> Don W3FPR
>
> On 3/9/2019 1:50 PM, Peter Dougherty wrote:
> > HI guys,
> > I'm still having a serious problem on 80m with my KPA1500.
> >
> > With the amp inline I'm getting high reflected power fault
> > everywhere below about 3675. My antenna (an inverted vee) is
> > resonant at 3550, and the SWR is below 2:1 from 3500 to 3630.
> >
> >
> >
> > This was happening in the past as well, and prompted me to
> > completely rebuild the antenna last summer. The antenna is fed with
> > 100' of brand new Davis BuryFlex feedline, a brand-new 5kW-rated
> > Balun Designs 1:1 current balun, new 12 AWG copper-clad steel wire, even new heavy ceramic insulators!
> >
> >
> > Without the amp everything's fine. I can push 100W through to the
> > antenna all day; the SWR LEDs on the amp (bypassed) show two green and that's it.
> > It's fine on every other band, including 80/75 phone.
> >
> >
> >
> > With the amp in, If I drop the drive to 10W or less, the amp is
> > happy and I get about 450 Watts out. But the instant I drive it with
> > ~15 Watts (when the K3s kicks the high power module in, and I hear
> > the internal relay click, I get the HI SWR warning and the amp
> > faults. 100% repeatable. Doesn't matter if the tuner is in or
> > out..there's NO way to get high power out of the KPA on 80 CW.
> ______________________________________________________________
> 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

Lovin' my K3S (S/N 10023)
73, Peter W2IRT

john@kk9a.com

Re: 80m KPA1500 High reflected power problems

In reply to this post by Peter W2IRT

So above 3.675 it works fine? Weird. When you say it was happening
previously, is that also with the KPA1500? First I would try another amp and
watch the SWR. I would also try bybassing any lightning protection devices
and coax relays so you just have coax and an antenna connected to the amp.

GL
John KK9A

Peter Dougherty W2IRT wrote:

HI guys,
I'm still having a serious problem on 80m with my KPA1500.

With the amp inline I'm getting high reflected power fault everywhere below
about 3675. My antenna (an inverted vee) is resonant at 3550, and the SWR is
below 2:1 from 3500 to 3630.

This was happening in the past as well, and prompted me to completely
rebuild the antenna last summer. The antenna is fed with 100' of brand new
Davis BuryFlex feedline, a brand-new 5kW-rated Balun Designs 1:1 current
balun, new 12 AWG copper-clad steel wire, even new heavy ceramic insulators!

Without the amp everything's fine. I can push 100W through to the antenna
all day; the SWR LEDs on the amp (bypassed) show two green and that's it.
It's fine on every other band, including 80/75 phone.

With the amp in, If I drop the drive to 10W or less, the amp is happy and I
get about 450 Watts out. But the instant I drive it with ~15 Watts (when the
K3s kicks the high power module in, and I hear the internal relay click, I
get the HI SWR warning and the amp faults. 100% repeatable. Doesn't matter
if the tuner is in or out..there's NO way to get high power out of the KPA
on 80 CW.

More details: If the KPA's tuner is bypassed it just faults instantly. If
the tuner is placed inline and I find a match, I can get about a second's or
two's worth of power before the SWR LEDs start lighting up, then the fault
happens.

Any idea what's going on here? This is unbelievably frustrating

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Jim Brown-10

Re: 80m KPA1500 High reflected power problems

> Peter Dougherty W2IRT wrote:
>
> HI guys,
> I'm still having a serious problem on 80m with my KPA1500.
>
> With the amp inline I'm getting high reflected power fault everywhere below
> about 3675. My antenna (an inverted vee) is resonant at 3550, and the SWR is
> below 2:1 from 3500 to 3630.

Hi Peter,

The KPA 1500 has a built-in antenna tuner. Is it possible that it's not
set up, or is not set up correctly, or is not being used correctly?
Perhaps the wrong operating mode for it, or it's calling up wrong
memorized settings? I don't own one, but borrowed one from K6XX while
he was at WRTC. I mostly used it on 6M, plus the few hours 20M was open
to DL enough to work the WRTC stations.

73, Jim K9YC

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Peter W2IRT

Re: 80m KPA1500 High reflected power problems

Jim, this is with the internal tuner in either mode--bypassed or inline. If I sit on 3504, I'm about 1.65:1 natively. I could run that without a tuner or with. But in either case, it faults out instantly with QRO power applied. The SWR seems to go haywire on the lower frequency ranges of the 80m band.

- pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Jim Brown
Sent: Saturday, March 9, 2019 5:46 PM
To: [hidden email]
Subject: Re: [Elecraft] 80m KPA1500 High reflected power problems

Hi Peter,

The KPA 1500 has a built-in antenna tuner. Is it possible that it's not set up, or is not set up correctly, or is not being used correctly? Perhaps the wrong operating mode for it, or it's calling up wrong memorized settings? I don't own one, but borrowed one from K6XX while he was at WRTC. I mostly used it on 6M, plus the few hours 20M was open to DL enough to work the WRTC stations.

73, Jim K9YC

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Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Michael Walker

Re: 80m KPA1500 High reflected power problems

You may want to try choking the feedline at the antenna and more importantly at the amp end with mix 31 or 43 chokes.

The high swr is likely the symptom not the problem.

Mike va3mw

> On Mar 9, 2019, at 10:05 PM, Peter Dougherty <[hidden email]> wrote:
>
> Jim, this is with the internal tuner in either mode--bypassed or inline. If I sit on 3504, I'm about 1.65:1 natively. I could run that without a tuner or with. But in either case, it faults out instantly with QRO power applied. The SWR seems to go haywire on the lower frequency ranges of the 80m band.
>
> - pjd
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On Behalf Of Jim Brown
> Sent: Saturday, March 9, 2019 5:46 PM
> To: [hidden email]
> Subject: Re: [Elecraft] 80m KPA1500 High reflected power problems
>
> Hi Peter,
>
> The KPA 1500 has a built-in antenna tuner. Is it possible that it's not set up, or is not set up correctly, or is not being used correctly? Perhaps the wrong operating mode for it, or it's calling up wrong memorized settings? I don't own one, but borrowed one from K6XX while he was at WRTC. I mostly used it on 6M, plus the few hours 20M was open to DL enough to work the WRTC stations.
>
> 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
>
> ______________________________________________________________
> 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

Peter W2IRT

Re: 80m KPA1500 High reflected power problems

In reply to this post by john@kk9a.com

John, I know there were some issues with my old tube amp, but it did load
enough to get me 275-odd DXCC entities with 1500W on 80 CW. The KPA has
never been used in the past on 80 since I was having antenna trouble (one
end was down all winter and it just got fixed today).

Everything's snow covered out the back so I don't want to play around at the
coax switch at the moment. I'll try bypassing the switch when it's a bit
warmer and the snow is gone.

Of note, last year with the weird SWR, the "old antenna" (same physical
space and height, just all different materials) was cut to 3750 and I used a
tuner for the bottom end. I found the tuner kept giving me "unable to find a
match" when I tried tuning with high power from my tube amp. I figured
replacing every factor in that chain would fix the issue; the only thing
that's the same is the antenna switch and the physical orientation of the
wires themselves. New amp, new coax, new balun, new wire, insulators and
even the support ropes were changed out.

- pjd

-----Original Message-----
From: [hidden email] <[hidden email]>
Sent: Saturday, March 9, 2019 4:55 PM
To: [hidden email]
Cc: [hidden email]
Subject: re: [Elecraft] 80m KPA1500 High reflected power problems

So above 3.675 it works fine? Weird. When you say it was happening
previously, is that also with the KPA1500? First I would try another amp and
watch the SWR. I would also try bybassing any lightning protection devices
and coax relays so you just have coax and an antenna connected to the amp.

GL
John KK9A

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Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Don Wilhelm

Re: 80m KPA1500 High reflected power problems

Peter,

If your antenna end insulators are covered with ice and snow, it is
entirely possible that the ice/snow covering will not show conductivity
with low power, but will become conductive at high power. That will
make whatever material you are using to support the antenna ends a part
of the antenna radiator - effectively lengthening the antenna.

Shake the snow and ice from the end insulators and/or use longer end
insulators and there is a good chance your problem will go away.

73,
Don W3FPR

On 3/9/2019 10:17 PM, Peter Dougherty wrote:

> John, I know there were some issues with my old tube amp, but it did load
> enough to get me 275-odd DXCC entities with 1500W on 80 CW. The KPA has
> never been used in the past on 80 since I was having antenna trouble (one
> end was down all winter and it just got fixed today).
>
> Everything's snow covered out the back so I don't want to play around at the
> coax switch at the moment. I'll try bypassing the switch when it's a bit
> warmer and the snow is gone.
>
> Of note, last year with the weird SWR, the "old antenna" (same physical
> space and height, just all different materials) was cut to 3750 and I used a
> tuner for the bottom end. I found the tuner kept giving me "unable to find a
> match" when I tried tuning with high power from my tube amp. I figured
> replacing every factor in that chain would fix the issue; the only thing
> that's the same is the antenna switch and the physical orientation of the
> wires themselves. New amp, new coax, new balun, new wire, insulators and
> even the support ropes were changed out.
>

Jim Brown-10

Re: 80m KPA1500 High reflected power problems

In reply to this post by Michael Walker

On 3/9/2019 7:13 PM, Michael Walker wrote:
> You may want to try choking the feedline at the antenna

Always a good thing.

> and more importantly at the amp end
No, the FEEDPOINT is the most important place for the first choke in any
antenna system. The purpose of a second choke on an antenna like a
dipole is to prevent it from acting as a parasitic element to a nearby
vertical.
> with mix 31

Yes.

> or 43 chokes.

I've recently completed a year's worth of extensive lab work that has
convinced me that #43 is NOT a good material for HF chokes. Ditto for
the #52 material that G3TXQ recommended. Two characteristics combine to
make it a poor choice. First, it's a relatively high Q material, so the
resonance it produces can get very narrow. Second, like all Fair-Rite
parts, it's a wide tolerance part -- +/- 20%. A part at the low end of
the tolerance range will produce a very different choke (resonance in
the wrong place, very narrow bandwidth, wider resonance and not high
enough impedance.

That work has produced, among other things, an all new cookbook with
greatly improved designs. k9yc.com/2018Cookbook.pdf

As to Peter's problem -- I'm inclined to agree with Don that something
may be arcing in the antenna system and causing a true fault.

73, Jim K9YC

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Grant Youngman-2

Re: 80m KPA1500 High reflected power problems

Great info. Thanks, Jim …

Grant NQ5T
K3 #2091 KX3 #8342

>
> I've recently completed a year's worth of extensive lab work that has convinced me that #43 is NOT a good material for HF chokes. Ditto for the #52 material that G3TXQ recommended. Two characteristics combine to make it a poor choice. First, it's a relatively high Q material, so the resonance it produces can get very narrow. Second, like all Fair-Rite parts, it's a wide tolerance part -- +/- 20%. A part at the low end of the tolerance range will produce a very different choke (resonance in the wrong place, very narrow bandwidth, wider resonance and not high enough impedance.
>

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john@kk9a.com

Re: 80m KPA1500 High reflected power problems

In reply to this post by Don Wilhelm

And the dipole wire (especially the ends) needs to be away from branches, shrubs ,etc.

John KK9A

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Saturday, March 09, 2019 11:07 PM
To: Peter Dougherty; [hidden email]; [hidden email]
Subject: Re: [Elecraft] 80m KPA1500 High reflected power problems

Peter,

If your antenna end insulators are covered with ice and snow, it is
entirely possible that the ice/snow covering will not show conductivity
with low power, but will become conductive at high power. That will
make whatever material you are using to support the antenna ends a part
of the antenna radiator - effectively lengthening the antenna.

Shake the snow and ice from the end insulators and/or use longer end
insulators and there is a good chance your problem will go away.

73,
Don W3FPR

On 3/9/2019 10:17 PM, Peter Dougherty wrote: