[Elecraft] 80m KPA1500 High reflected power problems

Sat Mar 9 15:09:54 EST 2019

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 <ww3s at zoominternet.net> 
Sent: Saturday, March 9, 2019 2:09 PM
To: donwilh at embarqmail.com
Cc: Elecraft at mailman.qth.net; Peter Dougherty <lists at w2irt.net>
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 <donwilh at embarqmail.com> 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.
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