KPA-1500 faulting on 6m; SWR issues

[Peter W2IRT]

Hi all (and sorry about the blank post-I don't know what happened there).

 

I am experiencing a continuing and repeatable problem with my KPA-1500 on
6m. With the amp in bypass I am able to operate normally with my K3s, but
the amp's meter is showing a 1.8 to 2:1 SWR on that band, despite
measurements on an AA-230 analyzer and the SWR meter on the K3s itself
showing it virtually flat (no more than 1.2:1).

Once the amp is placed set to operate it's still showing SWR measurements of
1.8:1 to 2.1:1 consistently when delivering power. If the tuner is bypassed
I can't run more than about 600W out before it faults. If I put the tuner in
and click it to tune, it will deliver power just fine at 1200 or 1300 Watts
for ONE FT8 transmit cycle. When it goes to transmit again it hard-faults
with too much reflected power. Using 100W straight from the K3s there is no
issue whatsoever, but *any* level of power from the KPA is liable to trip
the excess reflected power sensor on the amp.

At first I thought I had an antenna problem, but yesterday I put up a brand
new 6m LFA and it's doing the same thing. This coming week I plan to replace
the feedline with LMR-400--it's got a combination of 3/8" hardline and
RG-213 at the moment. Any thoughts on what might be going on here? Is there
a known-issue on 6m with the KPA?


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



President, North Jersey DX Association

DXCC Card Checker
Letter O Manager, ARRL Incoming 2nd District QSL bureau

 

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[Jim AB3CV]

I run 1500w for JT65 EME. No problems. My antenna measures 1.4:1 on the
KPA1500 swr meter and therefore never engages ATU.

Have you vetted your feedline at 1500w? Many times something might be good
at low power and fail at 1500. neither the AA230 or K3s will stress such a
feedline.

I believe the AA230 will do TDR. What does that show? Have you inspected
each connector for corrosion?

jim ab3cv

On Sun, May 31, 2020 at 12:47 PM Peter Dougherty <[hidden email]> wrote:

> Hi all (and sorry about the blank post-I don't know what happened there).
>
>
>
> I am experiencing a continuing and repeatable problem with my KPA-1500 on
> 6m. With the amp in bypass I am able to operate normally with my K3s, but
> the amp's meter is showing a 1.8 to 2:1 SWR on that band, despite
> measurements on an AA-230 analyzer and the SWR meter on the K3s itself
> showing it virtually flat (no more than 1.2:1).
>
> Once the amp is placed set to operate it's still showing SWR measurements
> of
> 1.8:1 to 2.1:1 consistently when delivering power. If the tuner is bypassed
> I can't run more than about 600W out before it faults. If I put the tuner
> in
> and click it to tune, it will deliver power just fine at 1200 or 1300 Watts
> for ONE FT8 transmit cycle. When it goes to transmit again it hard-faults
> with too much reflected power. Using 100W straight from the K3s there is no
> issue whatsoever, but *any* level of power from the KPA is liable to trip
> the excess reflected power sensor on the amp.
>
> At first I thought I had an antenna problem, but yesterday I put up a brand
> new 6m LFA and it's doing the same thing. This coming week I plan to
> replace
> the feedline with LMR-400--it's got a combination of 3/8" hardline and
> RG-213 at the moment. Any thoughts on what might be going on here? Is there
> a known-issue on 6m with the KPA?
>
>
> ---------------------------------------------
> 73 and Good DX
> Peter, W2IRT
>
>
>
> President, North Jersey DX Association
>
> DXCC Card Checker
> Letter O Manager, ARRL Incoming 2nd District QSL bureau
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> 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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[Gary J Ferdinand]

Rule out or in the feed line. Put the amp into a dummy load and see if it trips.  Good Luck.

73/Gary W2CS

> On May 31, 2020, at 12:54 PM, Jim Miller <[hidden email]> wrote:
>
> I run 1500w for JT65 EME. No problems. My antenna measures 1.4:1 on the
> KPA1500 swr meter and therefore never engages ATU.
>
> Have you vetted your feedline at 1500w? Many times something might be good
> at low power and fail at 1500. neither the AA230 or K3s will stress such a
> feedline.
>
> I believe the AA230 will do TDR. What does that show? Have you inspected
> each connector for corrosion?
>
> jim ab3cv
>
> On Sun, May 31, 2020 at 12:47 PM Peter Dougherty <[hidden email] <mailto:[hidden email]>> wrote:
>
>> Hi all (and sorry about the blank post-I don't know what happened there).
>>
>>
>>
>> I am experiencing a continuing and repeatable problem with my KPA-1500 on
>> 6m. With the amp in bypass I am able to operate normally with my K3s, but
>> the amp's meter is showing a 1.8 to 2:1 SWR on that band, despite
>> measurements on an AA-230 analyzer and the SWR meter on the K3s itself
>> showing it virtually flat (no more than 1.2:1).
>>
>> Once the amp is placed set to operate it's still showing SWR measurements
>> of
>> 1.8:1 to 2.1:1 consistently when delivering power. If the tuner is bypassed
>> I can't run more than about 600W out before it faults. If I put the tuner
>> in
>> and click it to tune, it will deliver power just fine at 1200 or 1300 Watts
>> for ONE FT8 transmit cycle. When it goes to transmit again it hard-faults
>> with too much reflected power. Using 100W straight from the K3s there is no
>> issue whatsoever, but *any* level of power from the KPA is liable to trip
>> the excess reflected power sensor on the amp.
>>
>> At first I thought I had an antenna problem, but yesterday I put up a brand
>> new 6m LFA and it's doing the same thing. This coming week I plan to
>> replace
>> the feedline with LMR-400--it's got a combination of 3/8" hardline and
>> RG-213 at the moment. Any thoughts on what might be going on here? Is there
>> a known-issue on 6m with the KPA?
>>
>>
>> ---------------------------------------------
>> 73 and Good DX
>> Peter, W2IRT
>>
>>
>>
>> President, North Jersey DX Association
>>
>> DXCC Card Checker
>> Letter O Manager, ARRL Incoming 2nd District QSL bureau
>>
>>
>>
>> ______________________________________________________________
>> 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] <mailto:[hidden email]>
>>
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[Lou W0FK]

Peter, how old is your amp? I have s/n 153, and had a similar issue on 6. One
of the torroids in, I believe, the low pass filter, ultimately burned out.
Smoke smells from your amp are not pleasant. The factory determined that the
torrid was delivered out of spec, and it was replaced. I suggest you get
with support and let them trouble shoot the issue. It may be something
completely different, but could still be problematic.

73, Lou W0FK



--
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[Jim Brown-10]

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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I am not familiar with the KPA1500 but I am wondering if the tuner is  
causing the poor SWR on your good 6m antenna?  Is it bypassed?

John KK9A


Peter Dougherty w2irt wrote:


I have never driven the amp with 90 Watts. Ever. The 90W figure is  
what comes out of the K3s *after* the amp has tripped out. With the  
amp in 'operate' I feed it typically 25-35 Watts.

Here are the error codes, as requested (truncated for length--there  
are MANY more):
441 20-06-01T01:02:22 FLT 90 - PWR REFL  freq 50304 inp 13W fwd 1064W  
refl 198W swr 2.5 23A 32C adc 280 var 198
440 20-05-31T23:45:57 FLT 90 - PWR REFL  freq 50008 inp 22W fwd 1356W  
refl 199W swr 2.2 44A 45C adc 281 var 199
439 20-05-31T23:43:46 OVR 90 - PWR REFL  freq 50304 inp 23W fwd 1210W  
refl 172W swr 2.2 39A 31C adc 257 var 172
438 20-05-31T23:43:39 OVR 90 - PWR REFL  freq 50304 inp 23W fwd 1204W  
refl 172W swr 2.2 39A 28C adc 257 var 172
437 20-05-31T23:43:13 FLT 90 - PWR REFL  freq 50304 inp 23W fwd 1298W  
refl 202W swr 2.3 44A 27C adc 284 var 202
435 20-05-31T02:39:03 OVR 90 - PWR REFL  freq 50304 inp 14W fwd 1107W  
refl 178W swr 2.3 23A 47C adc 262 var 178
434 20-05-31T02:34:03 FLT 90 - PWR REFL  freq 50304 inp 15W fwd 1152W  
refl 198W swr 2.4 28A 33C adc 280 var 198
433 20-05-31T02:25:03 OVR 90 - PWR REFL  freq 50304 inp 15W fwd 1130W  
refl 187W swr 2.3 24A 43C adc 270 var 187
432 20-05-31T02:23:03 FLT 90 - PWR REFL  freq 50304 inp 18W fwd 1165W  
refl 199W swr 2.4 40A 43C adc 281 var 199
431 20-05-31T02:21:33 FLT 90 - PWR REFL  freq 50304 inp 20W fwd 1189W  
refl 201W swr 2.3 46A 48C adc 283 var 201


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