http://elecraft.85.s1.nabble.com/Re-NOT-the-feedline-was-KPA-1500-faulting-on-6m-SWR-issues-tp7661502p7661510.html
Are you using the same output connector on the KPA1500 for the dummy load and the antenna?
> 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
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