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 <li...@w2irt.net> 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 <vk4...@gmail.com>
Sent: Sunday, May 31, 2020 11:05 PM
To: Peter Dougherty <li...@w2irt.net>; 'Paul Baldock' <
p...@paulbaldock.com>; elecraft@mailman.qth.net
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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