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Strange KPA500 problem on 6M

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Carl Yaffey

Strange KPA500 problem on 6M

Bottom line: I can’t get more than 200 watts out of my new KPA500 on 6M. It faults (HI SWR FAULT) when I try to increase the drive in order to get more output.
But I get full power on 6 with a dummy load.

Bad antenna? Don’t think so. Here’s my setup:
3 element M2 6M beam fed with high cost, low loss coax. Very low SWR and works great until I try to get more than 200 watts out of the amp.
I also have an R8 vertical and an HF dipole, both of which tune up on 6 with my new KAT500.
When running the amp at 200 watts, the swr indicator shows low swr with the KAT500 and any of the 3 antennas. As soon as I increase the drive with any of the 3 antennas, I get the fault.
When running the amp without the KAT and the beam hooked directly in, same fault when increasing drive.

The beam looks good in an MFJ antenna analyzer as does the R8.

So, I think the amp must be extremely sensitive to anything other than a pure 1:1 load as provided by the dummy load.
Your thoughts?
Carl, K8NU

Carl Yaffey K8NU

Recording studio.
[hidden email]
614 268 6353, Columbus OH
http://www.carl-yaffey.com
http://www.grassahol.com
http://www.bluesswing.com

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tomb18

Re: Strange KPA500 problem on 6M

HiI had the same with a 160m antenna. Turned out to be a connector that would fail over 120w . Obviously it's not the kpa500. Tom

Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: Carl Yaffey <[hidden email]> Date: 2016-12-03 4:57 PM (GMT-05:00) To: Elecraft List <[hidden email]> Subject: [Elecraft] Strange KPA500 problem on 6M
Bottom line: I can’t get more than 200 watts out of my new KPA500 on 6M. It faults (HI SWR FAULT) when I try to increase the drive in order to get more output.
But I get full power on 6 with a dummy load.

Bad antenna? Don’t think so. Here’s my setup:
3 element M2 6M beam fed with high cost, low loss coax. Very low SWR and works great until I try to get more than 200 watts out of the amp.
I also have an R8 vertical and an HF dipole, both of which tune up on 6 with my new KAT500.
When running the amp at 200 watts, the swr indicator shows low swr with the KAT500 and any of the 3 antennas. As soon as I increase the drive with any of the 3 antennas, I get the fault.
When running the amp without the KAT and the beam hooked directly in, same fault when increasing drive.

The beam looks good in an MFJ antenna analyzer as does the R8.

So, I think the amp must be extremely sensitive to anything other than a pure 1:1 load as provided by the dummy load.
Your thoughts?
Carl, K8NU

Carl Yaffey K8NU

Recording studio.
[hidden email]
614 268 6353, Columbus OH
http://www.carl-yaffey.com
http://www.grassahol.com
http://www.bluesswing.com

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Re: Strange KPA500 problem on 6M

In reply to this post by Carl Yaffey

Are you sure its only putting out 200 watts on 6 ??? MIne started acting that way a few weeks after I assembled it , was perfect whenI first ran thru the tests but later started doing exactly waht you describe . With an external Array Solutions Powermaster wattmeter and good dummy load it was in fact putting out more than 500 watts when the meter said 200 watts or so. Look at votlage and current and see how they compare with say 10 meters . FWIW - mine runs about 14.2 amps and 62.4 volts on 28.025 mhz for 500 out and on 50.1 mhz about 15.8 amps at 61.5 volts. Wattmeter reads withing about 10 watts or so compared to my AS Powermaster . SWR of my dummy load with all the assorted cabling using ANT3 port after letting it tune with the DL runs about 1.1 on 6 and 1.2 on 10 KPA500 readings - the Powermaster says its a tad better . All I can figure is its little digital brain got confused in mine and the 6 meter calibration went to pot - I re set it and it has been fine ever since. Manual tells how to do that . Anyhow something to look at . 73 Hank K7HP ----- Original Message -----

> Bottom line: I can’t get more than 200 watts out of my new KPA500 on
> 6M. It faults (HI SWR FAULT) when I try to increase the drive in order
> to get more output.
> But I get full power on 6 with a dummy load.
> Bad antenna? Don’t think so. Here’s my setup:
> 3 element M2 6M beam fed with high cost, low loss coax. Very low SWR
> and works great until I try to get more than 200 watts out of the amp.
> I also have an R8 vertical and an HF dipole, both of which tune up on
> 6 with my new KAT500.
> When running the amp at 200 watts, the swr indicator shows low swr
> with the KAT500 and any of the 3 antennas. As soon as I increase the
> drive with any of the 3 antennas, I get the fault.
> When running the amp without the KAT and the beam hooked directly in,
> same fault when increasing drive.
> The beam looks good in an MFJ antenna analyzer as does the R8.
> So, I think the amp must be extremely sensitive to anything other than
> a pure 1:1 load as provided by the dummy load.
> Your thoughts?
> Carl, K8NU
> Carl Yaffey K8NU
> Recording studio.
> [hidden email]
> 614 268 6353, Columbus OH
> http://www.carl-yaffey.com
> http://www.grassahol.com
> http://www.bluesswing.com
> ______________________________________________________________
> 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]

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Vic Rosenthal

Re: Strange KPA500 problem on 6M

In reply to this post by Carl Yaffey

Look at any cables, switches and connectors that are common to the various antennas. If it is OK with the dummy load, that points to it not being the KPA.

Vic 4X6GP

> On 3 Dec 2016, at 23:57, Carl Yaffey <[hidden email]> wrote:
>
> Bottom line: I can’t get more than 200 watts out of my new KPA500 on 6M. It faults (HI SWR FAULT) when I try to increase the drive in order to get more output.
> But I get full power on 6 with a dummy load.
>
> Bad antenna? Don’t think so. Here’s my setup:
> 3 element M2 6M beam fed with high cost, low loss coax. Very low SWR and works great until I try to get more than 200 watts out of the amp.
> I also have an R8 vertical and an HF dipole, both of which tune up on 6 with my new KAT500.
> When running the amp at 200 watts, the swr indicator shows low swr with the KAT500 and any of the 3 antennas. As soon as I increase the drive with any of the 3 antennas, I get the fault.
> When running the amp without the KAT and the beam hooked directly in, same fault when increasing drive.
>
> The beam looks good in an MFJ antenna analyzer as does the R8.
>
> So, I think the amp must be extremely sensitive to anything other than a pure 1:1 load as provided by the dummy load.
> Your thoughts?
> Carl, K8NU
>
>
>
> Carl Yaffey K8NU
>
> Recording studio.
> [hidden email]
> 614 268 6353, Columbus OH
> http://www.carl-yaffey.com
> http://www.grassahol.com
> http://www.bluesswing.com
>
> ______________________________________________________________
> 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
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Jim Brown-10

Re: Strange KPA500 problem on 6M

On Sat,12/3/2016 9:41 PM, Vic Rosenthal wrote:
> Look at any cables, switches and connectors that are common to the various antennas.

Yes. Lots of "off-brand" coax is junk. So are most un-branded
connectors. If the PL29-style connector doesn't say Amphenol 83-1SP,
it's probably junk. How well is the connector soldered or crimped? If
crimped, was it done with the "official" crimper for the "official"
crimp connector that matches THAT specific coax? If not, it's suspect.

Are you using any of those shiny adapters that are sold at hamfests for
a few bucks? They're JUNK! Ask me how I know. :) They have caused me
many problems that were tricky to diagnose.

IMO, the only GOOD coax connectors say "Amphenol" on them, or are
ancient MIL-spec parts with MIL numbers stamped into them. I snap up
stuff like this when I find it at ham flea markets.

73, Jim K9YC

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Michael Walker

Re: Strange KPA500 problem on 6M

As quoted

If the amp works on a dummy load, then look beyond the amp at this time until you have eliminated everything else.

Somewhere else you are getting a voltage breakdown that is arcing and tripping off the amp due to high swr. An MFJ analyzer will not show that.

Mike va3mw

> On Dec 4, 2016, at 12:54 AM, Jim Brown <[hidden email]> wrote:
>
>> On Sat,12/3/2016 9:41 PM, Vic Rosenthal wrote:
>> Look at any cables, switches and connectors that are common to the various antennas.
>
> Yes. Lots of "off-brand" coax is junk. So are most un-branded connectors. If the PL29-style connector doesn't say Amphenol 83-1SP, it's probably junk. How well is the connector soldered or crimped? If crimped, was it done with the "official" crimper for the "official" crimp connector that matches THAT specific coax? If not, it's suspect.
>
> Are you using any of those shiny adapters that are sold at hamfests for a few bucks? They're JUNK! Ask me how I know. :) They have caused me many problems that were tricky to diagnose.
>
> IMO, the only GOOD coax connectors say "Amphenol" on them, or are ancient MIL-spec parts with MIL numbers stamped into them. I snap up stuff like this when I find it at ham flea markets.
>
> 73, Jim K9YC
>
> ______________________________________________________________
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w0mu

Re: Strange KPA500 problem on 6M

Low pass filter in line?

On 12/4/2016 6:30 AM, Mike va3mw wrote:

> As quoted
>
> If the amp works on a dummy load, then look beyond the amp at this time until you have eliminated everything else.
>
> Somewhere else you are getting a voltage breakdown that is arcing and tripping off the amp due to high swr. An MFJ analyzer will not show that.
>
> Mike va3mw
>
>> On Dec 4, 2016, at 12:54 AM, Jim Brown <[hidden email]> wrote:
>>
>>> On Sat,12/3/2016 9:41 PM, Vic Rosenthal wrote:
>>> Look at any cables, switches and connectors that are common to the various antennas.
>> Yes. Lots of "off-brand" coax is junk. So are most un-branded connectors. If the PL29-style connector doesn't say Amphenol 83-1SP, it's probably junk. How well is the connector soldered or crimped? If crimped, was it done with the "official" crimper for the "official" crimp connector that matches THAT specific coax? If not, it's suspect.
>>
>> Are you using any of those shiny adapters that are sold at hamfests for a few bucks? They're JUNK! Ask me how I know. :) They have caused me many problems that were tricky to diagnose.
>>
>> IMO, the only GOOD coax connectors say "Amphenol" on them, or are ancient MIL-spec parts with MIL numbers stamped into them. I snap up stuff like this when I find it at ham flea markets.
>>
>> 73, Jim K9YC
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> 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]
> ______________________________________________________________
> Elecraft mailing list
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>
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David Olean

Re: Strange KPA500 problem on 6M

Last summer a friend of mine got a new K3s and had problems with it on
just six meters. As soon as he raised power above about 10 watts, the
SWR reading went crazy and the rig gave high VSWR warnings. He checked
his six meter yagi with another SWR analyzer and the antenna checked
good. After goofing around with it and getting nowhere, he brought it
over to my place and we tried it on my six meter array. We saw the same
problem here, high VSWR, but with different combinations of antennas,
the K3s actually worked OK. It also worked fine into a dummy load. I
got suspicious and tested the K3s with a spectrum analyzer. Sure enough
the rig had a huge parasitic oscillation on about 27.4 MHz and with most
of the power there, you could see how the radio would show a high SWR.
It only appeared when the internal 100w PA kicked in. He did not have a
KPA-500. This was just a K3s.

He sent the K3s back to the factory along with some pictures of the HP
spectrum analyzer screen. I am not sure if they duplicated the problem
at the factory, but they applied a few changes to the PA and now it is
all OK. If the K3s was to have an unwanted oscillation, it would sure
mess up the KPA-500 and show high VSWR and maybe damage some filter
components. If all else fails, that may be a place to look.

Dave K1WHS

>
>
> On 12/4/2016 6:30 AM, Mike va3mw wrote:
>> As quoted
>>
>> If the amp works on a dummy load, then look beyond the amp at this
>> time until you have eliminated everything else.
>>
>> Somewhere else you are getting a voltage breakdown that is arcing and
>> tripping off the amp due to high swr. An MFJ analyzer will not show
>> that.
>>
>> Mike va3mw
>>
>>> On Dec 4, 2016, at 12:54 AM, Jim Brown <[hidden email]>
>>> wrote:
>>>
>>>> On Sat,12/3/2016 9:41 PM, Vic Rosenthal wrote:
>>>> Look at any cables, switches and connectors that are common to the
>>>> various antennas.
>>> Yes. Lots of "off-brand" coax is junk. So are most un-branded
>>> connectors. If the PL29-style connector doesn't say Amphenol 83-1SP,
>>> it's probably junk. How well is the connector soldered or crimped?
>>> If crimped, was it done with the "official" crimper for the
>>> "official" crimp connector that matches THAT specific coax? If not,
>>> it's suspect.
>>>
>>> Are you using any of those shiny adapters that are sold at hamfests
>>> for a few bucks? They're JUNK! Ask me how I know. :) They have
>>> caused me many problems that were tricky to diagnose.
>>>
>>> IMO, the only GOOD coax connectors say "Amphenol" on them, or are
>>> ancient MIL-spec parts with MIL numbers stamped into them. I snap up
>>> stuff like this when I find it at ham flea markets.
>>>
>>> 73, Jim K9YC
>>>

Carl Yaffey

Re: Strange KPA500 problem on 6M

Wow. That was a great job of problem solving. In my case, I get the KPA fault with just 8 watts of drive from the K3S. So I doubt that’s my issue.

Carl Yaffey K8NU
Recording studio.
[hidden email]
614 268 6353, Columbus OH
http://www.carl-yaffey.com
http://www.grassahol.com
http://www.bluesswing.com

On Dec 5, 2016, 2:07 PM -0500, David Olean <[hidden email]>, wrote:

> Last summer a friend of mine got a new K3s and had problems with it on
> just six meters. As soon as he raised power above about 10 watts, the
> SWR reading went crazy and the rig gave high VSWR warnings. He checked
> his six meter yagi with another SWR analyzer and the antenna checked
> good. After goofing around with it and getting nowhere, he brought it
> over to my place and we tried it on my six meter array. We saw the same
> problem here, high VSWR, but with different combinations of antennas,
> the K3s actually worked OK. It also worked fine into a dummy load. I
> got suspicious and tested the K3s with a spectrum analyzer. Sure enough
> the rig had a huge parasitic oscillation on about 27.4 MHz and with most
> of the power there, you could see how the radio would show a high SWR.
> It only appeared when the internal 100w PA kicked in. He did not have a
> KPA-500. This was just a K3s.
>
> He sent the K3s back to the factory along with some pictures of the HP
> spectrum analyzer screen. I am not sure if they duplicated the problem
> at the factory, but they applied a few changes to the PA and now it is
> all OK. If the K3s was to have an unwanted oscillation, it would sure
> mess up the KPA-500 and show high VSWR and maybe damage some filter
> components. If all else fails, that may be a place to look.
>
> Dave K1WHS
>
>
> >
> >
> > On 12/4/2016 6:30 AM, Mike va3mw wrote:
> > > As quoted
> > >
> > > If the amp works on a dummy load, then look beyond the amp at this
> > > time until you have eliminated everything else.
> > >
> > > Somewhere else you are getting a voltage breakdown that is arcing and
> > > tripping off the amp due to high swr. An MFJ analyzer will not show
> > > that.
> > >
> > > Mike va3mw
> > >
> > > > On Dec 4, 2016, at 12:54 AM, Jim Brown <[hidden email]
> > > > wrote:
> > > >
> > > > > On Sat,12/3/2016 9:41 PM, Vic Rosenthal wrote:
> > > > > Look at any cables, switches and connectors that are common to the
> > > > > various antennas.
> > > > Yes. Lots of "off-brand" coax is junk. So are most un-branded
> > > > connectors. If the PL29-style connector doesn't say Amphenol 83-1SP,
> > > > it's probably junk. How well is the connector soldered or crimped?
> > > > If crimped, was it done with the "official" crimper for the
> > > > "official" crimp connector that matches THAT specific coax? If not,
> > > > it's suspect.
> > > >
> > > > Are you using any of those shiny adapters that are sold at hamfests
> > > > for a few bucks? They're JUNK! Ask me how I know. :) They have
> > > > caused me many problems that were tricky to diagnose.
> > > >
> > > > IMO, the only GOOD coax connectors say "Amphenol" on them, or are
> > > > ancient MIL-spec parts with MIL numbers stamped into them. I snap up
> > > > stuff like this when I find it at ham flea markets.
> > > >
> > > > 73, Jim K9YC
> > > >
>
> ______________________________________________________________
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AJ8MH-Radio.Joe.Hutchens

Re: Strange KPA500 problem on 6M

Had a similar problem when working for Motorola. Couldn't get the SWR
down with the antenna connected. Even changed antennas. Dummy load OK.
Finally looked at the signal on a spectrum analyzer and 80% of the power
wasn't even close to the crystal frequency.

Did you try driving the amp with another radio? You would see the same
problem if the amp is oscillating.

I'm assuming the K3 works fine into the same antenna...

73,
Joe ( AJ8MH-Radio )

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