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KPA500 High Reflected Power Fault

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Nels Anderson

KPA500 High Reflected Power Fault

Been enjoying KPA500 #32 for a couple of days now. Haven't yet made a
lot of QSOs with it, but the extra power on RTTY and to bust a couple
SSB pile-ups has been welcome.

However, the amp does not like my 40m setup. As soon as I transmit it
instantly goes into high reflected power fault and shuts down. My
antenna is a 120 foot center fed wire using 1 inch ladder line and an
LDG 1 kw auto tuner. SWR on 40m is under 2:1 and the K3 and other rigs
I've used it with have always been happy with the antenna arrangement.

In experimenting I used the K3 tune function and reduced the power in
steps to see if I could reach a low enough power level that it would
operate, but even at 1 watt of drive the amp still instantly went into
fault.

On 80m it did the same thing the first time I tried it, but then I
manually tweaked the antenna tuner, got a lower SWR reading and then the
amp worked. On the higher bands that I've tried there has been no problem.

So, any idea what is causing this?

73 Nels K1UR

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wayne burdick

Re: KPA500 High Reflected Power Fault

Administrator

Nels,

The K3 and your other rigs may be happy with it at 100 W, but at 500 W
it may be more critical. The present SWR level (actually, the
reflected power) could be just barely faulting the amp. Did you try
reducing the drive a bit?

Also: Is there any reason why the LDG tuner can't find a little better
match?

I've forwarded this to our amp design team to see if they can give you
any additional advice.

73,
Wayne
N6KR

On May 15, 2011, at 8:00 AM, Nels Anderson wrote:

> Been enjoying KPA500 #32 for a couple of days now. Haven't yet made a
> lot of QSOs with it, but the extra power on RTTY and to bust a couple
> SSB pile-ups has been welcome.
>
> However, the amp does not like my 40m setup. As soon as I transmit it
> instantly goes into high reflected power fault and shuts down. My
> antenna is a 120 foot center fed wire using 1 inch ladder line and an
> LDG 1 kw auto tuner. SWR on 40m is under 2:1 and the K3 and other rigs
> I've used it with have always been happy with the antenna arrangement.
>
> In experimenting I used the K3 tune function and reduced the power in
> steps to see if I could reach a low enough power level that it would
> operate, but even at 1 watt of drive the amp still instantly went into
> fault.
>
> On 80m it did the same thing the first time I tried it, but then I
> manually tweaked the antenna tuner, got a lower SWR reading and then
> the
> amp worked. On the higher bands that I've tried there has been no
> problem.
>
> So, any idea what is causing this?
>
> 73 Nels K1UR
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
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Jim Brown-10

Re: KPA500 High Reflected Power Fault

On 5/15/2011 8:11 AM, Wayne Burdick wrote:
> Did you try reducing the drive a bit?

I had a beta version here for test during a RTTY contest with orders to
run it with all the lights lit. It occasionally saw SWR on the order of
2:1 and faulted. I simply dropped the drive a dB or so and it purred
along nicely.

> Also: Is there any reason why the LDG tuner can't find a little better
> match?

That was my major complaint with the LDG 1000 tuner that I had bought
new, and is why I quickly sold it.

73, Jim K9YC
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Nels Anderson

Re: KPA500 High Reflected Power Fault

I tried lowering the drive to 1 watt (using the tune function) and that
still triggers the fault.

I suspect I'll only have the LDG tuner until the KAT500 comes out! It
more or less gets the job done but I think it could do better and I'm
not eager to got back to the manual tuner I have.

73 Nels K1UR

On 5/15/2011 11:37 AM, Jim Brown wrote:

> On 5/15/2011 8:11 AM, Wayne Burdick wrote:
>> Did you try reducing the drive a bit?
> I had a beta version here for test during a RTTY contest with orders to
> run it with all the lights lit. It occasionally saw SWR on the order of
> 2:1 and faulted. I simply dropped the drive a dB or so and it purred
> along nicely.
>
>> Also: Is there any reason why the LDG tuner can't find a little better
>> match?
> That was my major complaint with the LDG 1000 tuner that I had bought
> new, and is why I quickly sold it.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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N5GE

Re: KPA500 High Reflected Power Fault

In reply to this post by Nels Anderson

Sounds to like your LDG Tuner can't match the load...

73,
Tom
Amateur Radio Operator N5GE

On Sun, 15 May 2011 11:00:57 -0400, Nels Anderson <[hidden email]> wrote:

>Been enjoying KPA500 #32 for a couple of days now. Haven't yet made a
>lot of QSOs with it, but the extra power on RTTY and to bust a couple
>SSB pile-ups has been welcome.
>
>However, the amp does not like my 40m setup. As soon as I transmit it
>instantly goes into high reflected power fault and shuts down. My
>antenna is a 120 foot center fed wire using 1 inch ladder line and an
>LDG 1 kw auto tuner. SWR on 40m is under 2:1 and the K3 and other rigs
>I've used it with have always been happy with the antenna arrangement.
>
>In experimenting I used the K3 tune function and reduced the power in
>steps to see if I could reach a low enough power level that it would
>operate, but even at 1 watt of drive the amp still instantly went into
>fault.
>
>On 80m it did the same thing the first time I tried it, but then I
>manually tweaked the antenna tuner, got a lower SWR reading and then the
>amp worked. On the higher bands that I've tried there has been no problem.
>
>So, any idea what is causing this?
>
>73 Nels K1UR
>
>______________________________________________________________
>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

Amateur Radio Operator N5GE

Dennis Moore

Re: KPA500 High Reflected Power Fault

Sounds similar to what my barefoot K2/100 was doing with an LDG tuner to
a multiband ladderline-fed doublet. It would tune up alright but as soon
as I started talking on 17m the tuner would go crazy. I replaced the
first few feet of feedline with dual coax, grounded the shields. That
moved the open twinlead a few more feet away from the rig, and it
presented a slightly different impedance to the tuner. No more problems.

I don't know what configuration you have between the
tuner/balun/feedline but you might start there.

73, Dennis NJ6G

On 5/15/2011 11:41 AM, [hidden email] wrote:

> Sounds to like your LDG Tuner can't match the load...
>
> 73,
> Tom
> Amateur Radio Operator N5GE
>
>
> On Sun, 15 May 2011 11:00:57 -0400, Nels Anderson<[hidden email]> wrote:
>
>> Been enjoying KPA500 #32 for a couple of days now. Haven't yet made a
>> lot of QSOs with it, but the extra power on RTTY and to bust a couple
>> SSB pile-ups has been welcome.
>>
>> However, the amp does not like my 40m setup. As soon as I transmit it
>> instantly goes into high reflected power fault and shuts down. My
>> antenna is a 120 foot center fed wire using 1 inch ladder line and an
>> LDG 1 kw auto tuner. SWR on 40m is under 2:1 and the K3 and other rigs
>> I've used it with have always been happy with the antenna arrangement.
>>
>> In experimenting I used the K3 tune function and reduced the power in
>> steps to see if I could reach a low enough power level that it would
>> operate, but even at 1 watt of drive the amp still instantly went into
>> fault.
>>
>> On 80m it did the same thing the first time I tried it, but then I
>> manually tweaked the antenna tuner, got a lower SWR reading and then the
>> amp worked. On the higher bands that I've tried there has been no problem.
>>
>> So, any idea what is causing this?
>>
>> 73 Nels K1UR

Mike WA8BXN

Re: KPA500 High Reflected Power Fault

If a tuner gets you to a good match at low power where there is a balun
involved, but you run into problems at high power, I would first suspect
that the balun is getting saturated. Using a balun between an antenna and
the tuner many times is not a good thing to do. Using a balanced line tuner
is really the best thing to do. Changing the length of feedline from antenna
to balun does change the impedance that the balun or tuner has to deal with.
And that chance can help at a specific frequency that has problems.

Using a single antenna on multiple bands is very attractive. Unfortunately
it is sometimes not an easy thing to do efficiently. In most cases antennas
are always a tradeoff. There are so many constraints we deal with. Lot sizes
deed restrictions, supports available, how much we can spend. You want a
great antenna system and unlimited budget? I'm sure someone can sell you the
land needed, someone can clear it, someone can put up multiple support
structures and good antennas for the bands of interest.

Most often what we wind up with is a compromise in one way or another. In
many cases that compromise, with careful study and understanding, can result
in a quite respectable antenna. The other trade off to consider is the time
spent in getting the best antenna versus getting on the air a lot with a
variety of antennas (or maybe just one).

I must confess that I probably spend more time brooding over what could be a
better antenna than getting on the air and making contacts with the fairly
decent antennas that I do have here.

73 - Mike WA8BXN

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MontyS

Re: KPA500 High Reflected Power Fault

Having hammed from college dorms to homes on acre lots (no rhombics in my past), I have settled on either an off-center fed 80 meter wire or an open-wire center fed 80 meter wire as the best compromise for an all-band antenna. My LDG-1000 tunes the latter just fine.

I use a home-made humongous balun just outside the house to "match" the open-wire line to 52-ohm coax. The balun was sold as a kit by a since-forgotten QST advertiser. The core is 4 inches and the wire teflon-insulated #12, I believe. It's mounted in an aluminum box. It handles 600 watts very nicely with no effects attributable to power levels. I tune the antenna with 25 watts, and that setting remains good with higher powers. I have used all bands 160-10 meters, although 160 really doesn't work well. I now also have a roof-mounted hexagonal beam for 20-10 meters.

Before QRO, I used an MFJ-949 with internal balun to "match" the antenna to a previously-owned 756 ProII. The K3 tuner "matches" it FB with its internal tuner.

Actually, I had a friend with rhombics on two MARS frequencies provided by USAF so he could conduct phone patches to floating ice islands north of mainland Canada and Thule, Greenland. Another story.

Monty K2DLJ

> If a tuner gets you to a good match at low power where there is a balun
> involved, but you run into problems at high power, I would first suspect
> that the balun is getting saturated. Using a balun between an antenna and
> the tuner many times is not a good thing to do. Using a balanced line tuner
> is really the best thing to do. Changing the length of feedline from antenna
> to balun does change the impedance that the balun or tuner has to deal with.
> And that chance can help at a specific frequency that has problems.
>
> Using a single antenna on multiple bands is very attractive. Unfortunately
> it is sometimes not an easy thing to do efficiently. In most cases antennas
> are always a tradeoff. There are so many constraints we deal with. Lot sizes
> deed restrictions, supports available, how much we can spend. You want a
> great antenna system and unlimited budget? I'm sure someone can sell you the
> land needed, someone can clear it, someone can put up multiple support
> structures and good antennas for the bands of interest.
>
> Most often what we wind up with is a compromise in one way or another. In
> many cases that compromise, with careful study and understanding, can result
> in a quite respectable antenna. The other trade off to consider is the time
> spent in getting the best antenna versus getting on the air a lot with a
> variety of antennas (or maybe just one).
>
> I must confess that I probably spend more time brooding over what could be a
> better antenna than getting on the air and making contacts with the fairly
> decent antennas that I do have here.
>
> 73 - Mike WA8BXN
>
> ______________________________________________________________
> 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

Gary Gregory

Re: KPA500 High Reflected Power Fault

Using a Balun after the tuner with 50 Ohm coax between is NOT the best way.
Sure you can make it work, but the resultant SWR may not be the
best. Inconsistencies will/may occur...YMMV

Too many papers on this subject have been written over the years to quote
here on this very subject and I suspect that the authors are correct in
their assessment.

A 40M double extended Zepp (170' flat top) with open wire feedline direct to
a tuner has served me well. Interesting lobe on 20M though, but great on
40M..:-)

73's
Gary

On 16 May 2011 21:05, Monty Shultes <[hidden email]> wrote:

> Having hammed from college dorms to homes on acre lots (no rhombics in my
> past), I have settled on either an off-center fed 80 meter wire or an
> open-wire center fed 80 meter wire as the best compromise for an all-band
> antenna. My LDG-1000 tunes the latter just fine.
>
> I use a home-made humongous balun just outside the house to "match" the
> open-wire line to 52-ohm coax. The balun was sold as a kit by a
> since-forgotten QST advertiser. The core is 4 inches and the wire
> teflon-insulated #12, I believe. It's mounted in an aluminum box. It
> handles 600 watts very nicely with no effects attributable to power levels.
> I tune the antenna with 25 watts, and that setting remains good with higher
> powers. I have used all bands 160-10 meters, although 160 really doesn't
> work well. I now also have a roof-mounted hexagonal beam for 20-10 meters.
>
> Before QRO, I used an MFJ-949 with internal balun to "match" the antenna to
> a previously-owned 756 ProII. The K3 tuner "matches" it FB with its
> internal tuner.
>
> Actually, I had a friend with rhombics on two MARS frequencies provided by
> USAF so he could conduct phone patches to floating ice islands north of
> mainland Canada and Thule, Greenland. Another story.
>
> Monty K2DLJ
>
>
> > If a tuner gets you to a good match at low power where there is a balun
> > involved, but you run into problems at high power, I would first suspect
> > that the balun is getting saturated. Using a balun between an antenna and
> > the tuner many times is not a good thing to do. Using a balanced line
> tuner
> > is really the best thing to do. Changing the length of feedline from
> antenna
> > to balun does change the impedance that the balun or tuner has to deal
> with.
> > And that chance can help at a specific frequency that has problems.
> >
> > Using a single antenna on multiple bands is very attractive.
> Unfortunately
> > it is sometimes not an easy thing to do efficiently. In most cases
> antennas
> > are always a tradeoff. There are so many constraints we deal with. Lot
> sizes
> > deed restrictions, supports available, how much we can spend. You want a
> > great antenna system and unlimited budget? I'm sure someone can sell you
> the
> > land needed, someone can clear it, someone can put up multiple support
> > structures and good antennas for the bands of interest.
> >
> > Most often what we wind up with is a compromise in one way or another. In
> > many cases that compromise, with careful study and understanding, can
> result
> > in a quite respectable antenna. The other trade off to consider is the
> time
> > spent in getting the best antenna versus getting on the air a lot with a
> > variety of antennas (or maybe just one).
> >
> > I must confess that I probably spend more time brooding over what could
> be a
> > better antenna than getting on the air and making contacts with the
> fairly
> > decent antennas that I do have here.
> >
> > 73 - Mike WA8BXN
> >
> > ______________________________________________________________
> > 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
>
> ______________________________________________________________
> 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
>

--

VK4FD - Motorhome Mobile
Elecraft Equipment
K3 #679, KPA-500 #018
Living the dream!!!
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Gary Gregory

Re: KPA500 High Reflected Power Fault

Oh, and I forgot...the 'Fault' which was the original subject matter before
it morphed into the current postings lay not in the tuner or the amplifier,
but rather another 'item' used in the system...I believe he has it all fixed
and is busily working DX...:-)

73's
Gary

On 16 May 2011 21:16, Gary Gregory <[hidden email]> wrote:

> Using a Balun after the tuner with 50 Ohm coax between is NOT the best way.
> Sure you can make it work, but the resultant SWR may not be the
> best. Inconsistencies will/may occur...YMMV
>
> Too many papers on this subject have been written over the years to quote
> here on this very subject and I suspect that the authors are correct in
> their assessment.
>
> A 40M double extended Zepp (170' flat top) with open wire feedline direct
> to a tuner has served me well. Interesting lobe on 20M though, but great on
> 40M..:-)
>
>
> 73's
> Gary
>
>
> On 16 May 2011 21:05, Monty Shultes <[hidden email]> wrote:
>
>> Having hammed from college dorms to homes on acre lots (no rhombics in my
>> past), I have settled on either an off-center fed 80 meter wire or an
>> open-wire center fed 80 meter wire as the best compromise for an all-band
>> antenna. My LDG-1000 tunes the latter just fine.
>>
>> I use a home-made humongous balun just outside the house to "match" the
>> open-wire line to 52-ohm coax. The balun was sold as a kit by a
>> since-forgotten QST advertiser. The core is 4 inches and the wire
>> teflon-insulated #12, I believe. It's mounted in an aluminum box. It
>> handles 600 watts very nicely with no effects attributable to power levels.
>> I tune the antenna with 25 watts, and that setting remains good with higher
>> powers. I have used all bands 160-10 meters, although 160 really doesn't
>> work well. I now also have a roof-mounted hexagonal beam for 20-10 meters.
>>
>> Before QRO, I used an MFJ-949 with internal balun to "match" the antenna
>> to a previously-owned 756 ProII. The K3 tuner "matches" it FB with its
>> internal tuner.
>>
>> Actually, I had a friend with rhombics on two MARS frequencies provided by
>> USAF so he could conduct phone patches to floating ice islands north of
>> mainland Canada and Thule, Greenland. Another story.
>>
>> Monty K2DLJ
>>
>>
>> > If a tuner gets you to a good match at low power where there is a balun
>> > involved, but you run into problems at high power, I would first suspect
>> > that the balun is getting saturated. Using a balun between an antenna
>> and
>> > the tuner many times is not a good thing to do. Using a balanced line
>> tuner
>> > is really the best thing to do. Changing the length of feedline from
>> antenna
>> > to balun does change the impedance that the balun or tuner has to deal
>> with.
>> > And that chance can help at a specific frequency that has problems.
>> >
>> > Using a single antenna on multiple bands is very attractive.
>> Unfortunately
>> > it is sometimes not an easy thing to do efficiently. In most cases
>> antennas
>> > are always a tradeoff. There are so many constraints we deal with. Lot
>> sizes
>> > deed restrictions, supports available, how much we can spend. You want a
>> > great antenna system and unlimited budget? I'm sure someone can sell you
>> the
>> > land needed, someone can clear it, someone can put up multiple support
>> > structures and good antennas for the bands of interest.
>> >
>> > Most often what we wind up with is a compromise in one way or another.
>> In
>> > many cases that compromise, with careful study and understanding, can
>> result
>> > in a quite respectable antenna. The other trade off to consider is the
>> time
>> > spent in getting the best antenna versus getting on the air a lot with a
>> > variety of antennas (or maybe just one).
>> >
>> > I must confess that I probably spend more time brooding over what could
>> be a
>> > better antenna than getting on the air and making contacts with the
>> fairly
>> > decent antennas that I do have here.
>> >
>> > 73 - Mike WA8BXN
>> >
>> > ______________________________________________________________
>> > 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
>>
>> ______________________________________________________________
>> 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
>>
>
>
>
> --
>
> VK4FD - Motorhome Mobile
> Elecraft Equipment
> K3 #679, KPA-500 #018
> Living the dream!!!
>
>

Nels Anderson

Re: KPA500 High Reflected Power Fault

In reply to this post by Mike WA8BXN

Well, I found a solution to the problem. I had been using my old MFJ
manual tuner simply for its balun and antenna switch (tuning circuitry
bypassed). It appears at some point there was a failure in the metering
circuit. While trying things I noticed a burned resistor smell and when
I opened the box found several burned out parts on the sensor board. I
removed the board and just ran a bypass where it had been and the
problem is now gone. Had a long rag chew on 40m at 500w at the end of
the day and no issues at all.

I know antennas are often a compromise, but I've been using this one for
years and made lots of contacts on it (also have a triband yagi for
20/15/10). I'm the opposite of you, I spend most of my available time
operating rather than worrying about a better antenna. There's no one
solution that works for everyone.

73 Nels K1UR

On 5/15/2011 10:48 PM, Mike WA8BXN wrote:

>
> If a tuner gets you to a good match at low power where there is a balun
> involved, but you run into problems at high power, I would first suspect
> that the balun is getting saturated. Using a balun between an antenna and
> the tuner many times is not a good thing to do. Using a balanced line tuner
> is really the best thing to do. Changing the length of feedline from antenna
> to balun does change the impedance that the balun or tuner has to deal with.
> And that chance can help at a specific frequency that has problems.
>
> Using a single antenna on multiple bands is very attractive. Unfortunately
> it is sometimes not an easy thing to do efficiently. In most cases antennas
> are always a tradeoff. There are so many constraints we deal with. Lot sizes
> deed restrictions, supports available, how much we can spend. You want a
> great antenna system and unlimited budget? I'm sure someone can sell you the
> land needed, someone can clear it, someone can put up multiple support
> structures and good antennas for the bands of interest.
>
> Most often what we wind up with is a compromise in one way or another. In
> many cases that compromise, with careful study and understanding, can result
> in a quite respectable antenna. The other trade off to consider is the time
> spent in getting the best antenna versus getting on the air a lot with a
> variety of antennas (or maybe just one).
>
> I must confess that I probably spend more time brooding over what could be a
> better antenna than getting on the air and making contacts with the fairly
> decent antennas that I do have here.
>
> 73 - Mike WA8BXN
>
> ______________________________________________________________
> 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
>

Don Wilhelm-4

Re: KPA500 High Reflected Power Fault

In reply to this post by MontyS

The one piece of information that is left out of most discussions
about multiband antennas is the feedline length.
The feedline acts as an impedance transformer since it is not matched to
the antenna. Used in that way, the feedline type and length become an
important factor. That is why some work on some bands while others with
the same radiator length do not work the same.

73,
Don W3FPR

On 5/16/2011 7:05 AM, Monty Shultes wrote:
> Having hammed from college dorms to homes on acre lots (no rhombics in my past), I have settled on either an off-center fed 80 meter wire or an open-wire center fed 80 meter wire as the best compromise for an all-band antenna. My LDG-1000 tunes the latter just fine.
>
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Nr4c

Re: KPA500 High Reflected Power Fault

In reply to this post by Nels Anderson

Hi,

I don't have any experience with the LDG 1KW tuner, I assume this is
the 1000Pro. But, I have used several smaller LDG tuners and the newer
ones like the 200 PRO have a means of adjusting the SWR threshold so
that you can have the tuner stop trying when it gets "low enough". I
looked at the LDG site this morning and didn't see this in the product
description, but did notice that there is a FREE upgrade to this tuner
to add additional features including new algorithms for the tuning
process. Also peak and average meter modes. Offer is good till May 31
so get on it fast. They'll send you a new chip to insert in the tuner.

I hope this helps.

...bill nr4c

BTW: if this doesn't help, loan me the KPA500 for a while, you know,
maybe until thge Elecraft tuner makes it's appearance.

On Sun, 15 May 2011 11:00:57 -0400, Nels Anderson wrote: