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KPA-1500 SWR fault above 700-800 watts on 160m

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Ken Ramirez de Arellano

KPA-1500 SWR fault above 700-800 watts on 160m

Every bit of antenna hardware ( coax, balun, insulators, etc. have been
changed out or proven good. Connections are all solid. My KPA1500 will
transmit above 800 watts for about 15-30 seconds and then the SWR jumps up
and it faults out for high VSWR. I can run 1500 watts on all the other
“Legacy” bands (10,15,20,40,80) with no problems. I’ve forced an STU
relearn and still the same issue. The antenna B amp is a Clipperton L and
that transmits at a KW out and I see no change in VSWR in the external
wattmeter using all of the same cabling. It’s starting to look like
something heating up in the KPA1500. Is anyone aware of a known issue for
this with the KPA1500 or a known fix? I would rather do a field repair
instead of sending to Elecraft from KP4. TIA Ken, KP3MM
--
Ken Ramirez
KP3MM
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David Gilbert-2

Re: KPA-1500 SWR fault above 700-800 watts on 160m

If your Clipperton amp doesn't have the same problem then it does indeed
point to the KPA1500.

I don't own a KPA1500, but a quick look at the online manual shows that
the tuning unit is an L-Network. Depending upon the load the unit is
trying to match, an L-Network can require a very large amount of
capacitance, especially on 160m ... which I suspect is achieved in the
KPA1500 by switching in high power ceramic units for 160m. I had to
replace a couple of high power ceramic doorknob capacitors for 160m in
my own tube amp because I had degraded them with a high VSWR per my
earlier post about an overheating common mode choke.

Of course you might not have the same problem, but it would be one of
the things I'd check.

73,
Dave AB7E

On 9/2/2020 2:41 PM, Ken Ramirez de Arellano wrote:

> Every bit of antenna hardware ( coax, balun, insulators, etc. have been
> changed out or proven good. Connections are all solid. My KPA1500 will
> transmit above 800 watts for about 15-30 seconds and then the SWR jumps up
> and it faults out for high VSWR. I can run 1500 watts on all the other
> “Legacy” bands (10,15,20,40,80) with no problems. I’ve forced an STU
> relearn and still the same issue. The antenna B amp is a Clipperton L and
> that transmits at a KW out and I see no change in VSWR in the external
> wattmeter using all of the same cabling. It’s starting to look like
> something heating up in the KPA1500. Is anyone aware of a known issue for
> this with the KPA1500 or a known fix? I would rather do a field repair
> instead of sending to Elecraft from KP4. TIA Ken, KP3MM

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Alan - G4GNX

Re: KPA-1500 SWR fault above 700-800 watts on 160m

In reply to this post by Ken Ramirez de Arellano

Ken, sorry this is rather long, but here goes...............

I had a similar problem in the UK, with a OSCFD antenna, purchased from
a UK company. I didn't question the theory and just assembled it
according to instructions.

As you would expect the antenna is made from two differing lengths of
ruggedised, plastic coated copper wire, which is fed by a 4:1 Guanella
balun, rated at 400W. The balun is potted in a weatherproof box and is
fed via the customary PL259/SO239 connector with Mil Spec RG58 coaxial
cable. About 6' down from the feed point is a common mode choke
(sometimes called a sleeve balun) which consists of 8 ferrite inline
cores, around the co-ax and held in place with heat shrink sleeving and
cable ties.

The rig was just the K3S/100W with internal tuner and all was well for
many months, mostly using 40 metres SSB. A while later, I added the
KPA500/KAT500 combo which I ran for a couple of very short periods at
400W to test. For a weekly net, I used only 200W and all seemed OK for a
while, until suddenly the VSWR started to increase over the period of an
'over'. Over a few weeks this got more frequent and I would have to
re-tune part way through an 'over'. At that time, I wan't sure whether
it was an antenna issue, or the KPA500/KAT500, although I suspected that
the KPA500 was getting too hot, so I posted a question on a forum and
was contacted by Jack Brindle of Elecraft, who kindly looked at the
KPA500 fault reports and sent me a comprehensive explanation of his
findings based on the figures and his experience, which concluded that
the antenna was almost certainly the culprit.

I ordered a new 1KW Guanella balun and some much bigger ferrites, with
the intention of replacing the RG58 with Westflex 103. In the meantime I
soldiered on with the original setup until one day all hell let loose,
with the KPA500 and KAT500 fault lights flashing and even the K3S got
'ticked off'. At this point I switched to my HF vertical, to keep me on
the air.

When I dismantled the wire antenna, I expected a balun fault, but it was
actually OK. On further checking, after disconnecting the co-ax from the
balun, the open ended co-ax showed a DC short on a test meter!

I used the Rig Expert 600 to determine exactly where the short was and
it turned out to be exactly where the sleeve ferrites had been, BUT
there was no discoloration of the outer covering, or signs of melting,
so I knew it was unlikely that the ferrite cores had got heated. I cut
the section out of the co-ax and started to take it apart. With the
outer covering all removed, there was still no sign of discoloration of
the screen braid, but as I tried to remove the braid, it was obvious
that there had been considerable heating as the center section of the
braid has melted into the center conductor insulation, and somewhere in
there, it has made it right through to the center conductor.

Unfortunately I haven't yet found the exact point of the short, because
I left the partly dismantled piece of inner co-ax on a table and one of
my cats seems to have run off with it! :-D
When I eventually find it, I'll continue investigating.

In the meantime, one theory is that the common mode choke presented a
high impedance to RF coming back down the co-ax and this in turn
produced a very high voltage causing an arc between inner and outer and
as the characteristics changed, in turn a high current node was created,
which caused the heating effect. Another theory is that it is just a
crappy piece of cable and it just failed.

Unfortunately this is not the sort of fault that can be detected in its
development stage by a low power antenna analyser, it needs a fair
amount of power.

This long tale may just give you some clues to your possible issue on
160m although on a different power scale..

73,

Alan. G4GNX

------ Original Message ------
From: "Ken Ramirez de Arellano" <[hidden email]>
To: [hidden email]
Sent: 02/09/2020 22:41:30
Subject: [Elecraft] KPA-1500 SWR fault above 700-800 watts on 160m

>Every bit of antenna hardware ( coax, balun, insulators, etc. have been
>changed out or proven good. Connections are all solid. My KPA1500 will
>transmit above 800 watts for about 15-30 seconds and then the SWR jumps up
>and it faults out for high VSWR. I can run 1500 watts on all the other
>“Legacy” bands (10,15,20,40,80) with no problems. I’ve forced an STU
>relearn and still the same issue. The antenna B amp is a Clipperton L and
>that transmits at a KW out and I see no change in VSWR in the external
>wattmeter using all of the same cabling. It’s starting to look like
>something heating up in the KPA1500. Is anyone aware of a known issue for
>this with the KPA1500 or a known fix? I would rather do a field repair
>instead of sending to Elecraft from KP4. TIA Ken, KP3MM
>--
>Ken Ramirez
>KP3MM
>

Ronnie Hull

Re: KPA-1500 SWR fault above 700-800 watts on 160m

Update
I took the Balun designs 4:1 out of line and put a Dx Engineering maxi core 5kw 4:1 in its place. It tunes a little better on 160 but the KPA1500 finally faults out and says cannot find match and shows 9:1.... better than 99:1

So I put the KPA1500 straight to a 2.5kw bird dummy load and it tunes instantly 1:1 in 160M

So this fault is with the antenna for sure

The only other Balun I have to try is a DX Engineering 6:1 which I will try in the morning.

Failing that I will order a 1:1 feom DX Engineering

But at least I know it’s the antenna that is causing this problem

I’m going to also borrow a antenna analyzer tomorrow and see what gives.
Thanks for all the suggestions!

We will whip this yet

Ronnie w5sum

Sent from my iPhone

> On Sep 2, 2020, at 6:05 PM, Alan - G4GNX <[hidden email]> wrote:
>
> Ken, sorry this is rather long, but here goes...............
>
> I had a similar problem in the UK, with a OSCFD antenna, purchased from a UK company. I didn't question the theory and just assembled it according to instructions.
>
> As you would expect the antenna is made from two differing lengths of ruggedised, plastic coated copper wire, which is fed by a 4:1 Guanella balun, rated at 400W. The balun is potted in a weatherproof box and is fed via the customary PL259/SO239 connector with Mil Spec RG58 coaxial cable. About 6' down from the feed point is a common mode choke (sometimes called a sleeve balun) which consists of 8 ferrite inline cores, around the co-ax and held in place with heat shrink sleeving and cable ties.
>
> The rig was just the K3S/100W with internal tuner and all was well for many months, mostly using 40 metres SSB. A while later, I added the KPA500/KAT500 combo which I ran for a couple of very short periods at 400W to test. For a weekly net, I used only 200W and all seemed OK for a while, until suddenly the VSWR started to increase over the period of an 'over'. Over a few weeks this got more frequent and I would have to re-tune part way through an 'over'. At that time, I wan't sure whether it was an antenna issue, or the KPA500/KAT500, although I suspected that the KPA500 was getting too hot, so I posted a question on a forum and was contacted by Jack Brindle of Elecraft, who kindly looked at the KPA500 fault reports and sent me a comprehensive explanation of his findings based on the figures and his experience, which concluded that the antenna was almost certainly the culprit.
>
> I ordered a new 1KW Guanella balun and some much bigger ferrites, with the intention of replacing the RG58 with Westflex 103. In the meantime I soldiered on with the original setup until one day all hell let loose, with the KPA500 and KAT500 fault lights flashing and even the K3S got 'ticked off'. At this point I switched to my HF vertical, to keep me on the air.
>
> When I dismantled the wire antenna, I expected a balun fault, but it was actually OK. On further checking, after disconnecting the co-ax from the balun, the open ended co-ax showed a DC short on a test meter!
>
> I used the Rig Expert 600 to determine exactly where the short was and it turned out to be exactly where the sleeve ferrites had been, BUT there was no discoloration of the outer covering, or signs of melting, so I knew it was unlikely that the ferrite cores had got heated. I cut the section out of the co-ax and started to take it apart. With the outer covering all removed, there was still no sign of discoloration of the screen braid, but as I tried to remove the braid, it was obvious that there had been considerable heating as the center section of the braid has melted into the center conductor insulation, and somewhere in there, it has made it right through to the center conductor.
>
> Unfortunately I haven't yet found the exact point of the short, because I left the partly dismantled piece of inner co-ax on a table and one of my cats seems to have run off with it! :-D
> When I eventually find it, I'll continue investigating.
>
> In the meantime, one theory is that the common mode choke presented a high impedance to RF coming back down the co-ax and this in turn produced a very high voltage causing an arc between inner and outer and as the characteristics changed, in turn a high current node was created, which caused the heating effect. Another theory is that it is just a crappy piece of cable and it just failed.
>
> Unfortunately this is not the sort of fault that can be detected in its development stage by a low power antenna analyser, it needs a fair amount of power.
>
> This long tale may just give you some clues to your possible issue on 160m although on a different power scale..
>
> 73,
>
> Alan. G4GNX
>
>
> ------ Original Message ------
> From: "Ken Ramirez de Arellano" <[hidden email]>
> To: [hidden email]
> Sent: 02/09/2020 22:41:30
> Subject: [Elecraft] KPA-1500 SWR fault above 700-800 watts on 160m
>
>> Every bit of antenna hardware ( coax, balun, insulators, etc. have been
>> changed out or proven good. Connections are all solid. My KPA1500 will
>> transmit above 800 watts for about 15-30 seconds and then the SWR jumps up
>> and it faults out for high VSWR. I can run 1500 watts on all the other
>> “Legacy” bands (10,15,20,40,80) with no problems. I’ve forced an STU
>> relearn and still the same issue. The antenna B amp is a Clipperton L and
>> that transmits at a KW out and I see no change in VSWR in the external
>> wattmeter using all of the same cabling. It’s starting to look like
>> something heating up in the KPA1500. Is anyone aware of a known issue for
>> this with the KPA1500 or a known fix? I would rather do a field repair
>> instead of sending to Elecraft from KP4. TIA Ken, KP3MM
>> --
>> Ken Ramirez
>> KP3MM
>>
>
> ______________________________________________________________
> 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]

Roy Koeppe

KPA-1500 SWR fault above 700-800 watts on 160m

KPA1500 tuner is rated for maximum antenna SWR of just 3 to 1.

73, Roy K6XK

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Re: KPA-1500 SWR fault above 700-800 watts on 160m

In reply to this post by Ronnie Hull

Ronnie

You might try measuring the common mode current on your coax feed in various places, just a cheapo RF current meter clamped over the coax. That will tell you if the chokes you are using are doing their job. I know for sure that cmc causes considerable distortion of swr curves. Any antenna analyser will be fooled by cmc, so my 'umble advice is cure that with lots of ferrite wherever it's needed. I use K9YC-style chokes, eg several turns on 240-31 core, or, if it's really bad, several turns on several cores using 7" diameter turns (from memory, check his cookbook). I'm told this is cheaper and better than anything you can buy. Of course I know nothing about your layout but it has always helped me to ground the coax before it comes into the house. Apologies if I'm going over old stuff you've already done.

73 David G3UNA

> On 03 September 2020 at 00:30 Ronnie Hull <[hidden email]> wrote:
>
>
> Update
> I took the Balun designs 4:1 out of line and put a Dx Engineering maxi core 5kw 4:1 in its place. It tunes a little better on 160 but the KPA1500 finally faults out and says cannot find match and shows 9:1.... better than 99:1
>
> So I put the KPA1500 straight to a 2.5kw bird dummy load and it tunes instantly 1:1 in 160M
>
> So this fault is with the antenna for sure
>
> The only other Balun I have to try is a DX Engineering 6:1 which I will try in the morning.
>
> Failing that I will order a 1:1 feom DX Engineering
>
> But at least I know it’s the antenna that is causing this problem
>
> I’m going to also borrow a antenna analyzer tomorrow and see what gives.
> Thanks for all the suggestions!
>
> We will whip this yet
>
> Ronnie w5sum
>
> Sent from my iPhone
>
> > On Sep 2, 2020, at 6:05 PM, Alan - G4GNX <[hidden email]> wrote:
> >
> > Ken, sorry this is rather long, but here goes...............
> >
> > I had a similar problem in the UK, with a OSCFD antenna, purchased from a UK company. I didn't question the theory and just assembled it according to instructions.
> >
> > As you would expect the antenna is made from two differing lengths of ruggedised, plastic coated copper wire, which is fed by a 4:1 Guanella balun, rated at 400W. The balun is potted in a weatherproof box and is fed via the customary PL259/SO239 connector with Mil Spec RG58 coaxial cable. About 6' down from the feed point is a common mode choke (sometimes called a sleeve balun) which consists of 8 ferrite inline cores, around the co-ax and held in place with heat shrink sleeving and cable ties.
> >
> > The rig was just the K3S/100W with internal tuner and all was well for many months, mostly using 40 metres SSB. A while later, I added the KPA500/KAT500 combo which I ran for a couple of very short periods at 400W to test. For a weekly net, I used only 200W and all seemed OK for a while, until suddenly the VSWR started to increase over the period of an 'over'. Over a few weeks this got more frequent and I would have to re-tune part way through an 'over'. At that time, I wan't sure whether it was an antenna issue, or the KPA500/KAT500, although I suspected that the KPA500 was getting too hot, so I posted a question on a forum and was contacted by Jack Brindle of Elecraft, who kindly looked at the KPA500 fault reports and sent me a comprehensive explanation of his findings based on the figures and his experience, which concluded that the antenna was almost certainly the culprit.
> >
> > I ordered a new 1KW Guanella balun and some much bigger ferrites, with the intention of replacing the RG58 with Westflex 103. In the meantime I soldiered on with the original setup until one day all hell let loose, with the KPA500 and KAT500 fault lights flashing and even the K3S got 'ticked off'. At this point I switched to my HF vertical, to keep me on the air.
> >
> > When I dismantled the wire antenna, I expected a balun fault, but it was actually OK. On further checking, after disconnecting the co-ax from the balun, the open ended co-ax showed a DC short on a test meter!
> >
> > I used the Rig Expert 600 to determine exactly where the short was and it turned out to be exactly where the sleeve ferrites had been, BUT there was no discoloration of the outer covering, or signs of melting, so I knew it was unlikely that the ferrite cores had got heated. I cut the section out of the co-ax and started to take it apart. With the outer covering all removed, there was still no sign of discoloration of the screen braid, but as I tried to remove the braid, it was obvious that there had been considerable heating as the center section of the braid has melted into the center conductor insulation, and somewhere in there, it has made it right through to the center conductor.
> >
> > Unfortunately I haven't yet found the exact point of the short, because I left the partly dismantled piece of inner co-ax on a table and one of my cats seems to have run off with it! :-D
> > When I eventually find it, I'll continue investigating.
> >
> > In the meantime, one theory is that the common mode choke presented a high impedance to RF coming back down the co-ax and this in turn produced a very high voltage causing an arc between inner and outer and as the characteristics changed, in turn a high current node was created, which caused the heating effect. Another theory is that it is just a crappy piece of cable and it just failed.
> >
> > Unfortunately this is not the sort of fault that can be detected in its development stage by a low power antenna analyser, it needs a fair amount of power.
> >
> > This long tale may just give you some clues to your possible issue on 160m although on a different power scale..
> >
> > 73,
> >
> > Alan. G4GNX
> >
> >
> > ------ Original Message ------
> > From: "Ken Ramirez de Arellano" <[hidden email]>
> > To: [hidden email]
> > Sent: 02/09/2020 22:41:30
> > Subject: [Elecraft] KPA-1500 SWR fault above 700-800 watts on 160m
> >
> >> Every bit of antenna hardware ( coax, balun, insulators, etc. have been
> >> changed out or proven good. Connections are all solid. My KPA1500 will
> >> transmit above 800 watts for about 15-30 seconds and then the SWR jumps up
> >> and it faults out for high VSWR. I can run 1500 watts on all the other
> >> “Legacy” bands (10,15,20,40,80) with no problems. I’ve forced an STU
> >> relearn and still the same issue. The antenna B amp is a Clipperton L and
> >> that transmits at a KW out and I see no change in VSWR in the external
> >> wattmeter using all of the same cabling. It’s starting to look like
> >> something heating up in the KPA1500. Is anyone aware of a known issue for
> >> this with the KPA1500 or a known fix? I would rather do a field repair
> >> instead of sending to Elecraft from KP4. TIA Ken, KP3MM
> >> --
> >> Ken Ramirez
> >> KP3MM
> >>
> >
> > ______________________________________________________________
> > 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]
>
> ______________________________________________________________
> 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]

Jim Brown-10

Re: KPA-1500 SWR fault above 700-800 watts on 160m

On 9/3/2020 4:21 AM, CUTTER DAVID via Elecraft wrote:
> I use K9YC-style chokes, eg several turns on 240-31 core, or, if it's really bad, several turns on several cores using 7" diameter turns (from memory, check his cookbook). I'm told this is cheaper and better than anything you can buy. Of course I know nothing about your layout but it has always helped me to ground the coax before it comes into the house.

Hi David,

Note that, based on extensive research in 2017 and 2018, I no longer
recommend the older style of choke that you're using, and I revised the
RFI tutorial to reflect that. I published both that revision and the new
Cookbook late in 2018.

k9yc.com/publish.htm

The problem with the older style chokes (multiple turns of coax on
multiple #31 cores) is that 1) any "scrambling" of the winding reduces
choking impedance, and 2) variations in winding style (diameter,
spacing) make the chokes non-repeatable.

The new choke designs ARE repeatable, AND take into account the wide
manufacturing tolerances of all ferrite parts, which can significantly
affect the choking impedance and where the chokes are tuned. The work I
did in 2017 and 2018 included characterizing nearly 200 #31 cores
obtained from multiple vendors over about ten years, selecting cores at
the limits of those tolerances, winding and measuring hundreds of chokes
on those cores, tabulating the results, and making recommendations for
each band and each transmission line type based on worst case results
for each design. Chokes wound following the new 2018 Cookbook should
provide at least the specified response on any #31 core you buy. Note
that #31 mix is made ONLY by Fair-Rite.

Another point about measuring common mode current. As you have observed,
it varies along the line, simply because in the common mode circuit, the
feedline is part of the antenna, and both voltage and current vary along
the line conforming to wavelength relationships at the operating
frequency. A good choke forces a current minimum at the point where it
is inserted. How common mode current varies along the line depends on
the quality of the choke, the electrical length of the outer conductor
of the coax (VF~0.98), and how the shield is terminated on the other end
(grounded or floating using a link coupled tuner).

A choke is most useful at the antenna feedpoint (up in the air, or at
the feed end of a vertical or other long wire), which tends to minimize
common mode current all along the line, because it "disconnects" the
feedline from the antenna. A choke at any other point is FAR less
effective -- all it does force a current minimum at the point it is
inserted, leaving the feedline connected to the antenna, allowing common
mode current between the choke and the antenna, and coupling any noise
current to the antenna.

For this reason, the first choke in any system should ALWAYS be at the
antenna IF the antenna is matched to the feedline. The power handling of
my chokes are ONLY applicable if the feedline is matched at the point
where they are inserted. A choke inserted into a poorly matched or
un-matched line is much more likely to overheat and fail. Dissipation
(heating) is addressed in the 2018 Cookbook.

73, Jim K9YC
______________________________________________________________
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Re: KPA-1500 SWR fault above 700-800 watts on 160m

Hi Jim
Thanks for the new link. I must say we made several big chokes using the "old" method and our analyser wasn't good enough to measure the common mode impedance, so our conclusion was they were all above the analyser limit of several thousand ohms. I'm about to make a single core choke, so I'll take a look at the new info.

73 David G3UNA

> On 03 September 2020 at 17:05 Jim Brown <[hidden email]> wrote:
>
>
> On 9/3/2020 4:21 AM, CUTTER DAVID via Elecraft wrote:
> > I use K9YC-style chokes, eg several turns on 240-31 core, or, if it's really bad, several turns on several cores using 7" diameter turns (from memory, check his cookbook). I'm told this is cheaper and better than anything you can buy. Of course I know nothing about your layout but it has always helped me to ground the coax before it comes into the house.
>
> Hi David,
>
> Note that, based on extensive research in 2017 and 2018, I no longer
> recommend the older style of choke that you're using, and I revised the
> RFI tutorial to reflect that. I published both that revision and the new
> Cookbook late in 2018.
>
> k9yc.com/publish.htm
>
> The problem with the older style chokes (multiple turns of coax on
> multiple #31 cores) is that 1) any "scrambling" of the winding reduces
> choking impedance, and 2) variations in winding style (diameter,
> spacing) make the chokes non-repeatable.
>
> The new choke designs ARE repeatable, AND take into account the wide
> manufacturing tolerances of all ferrite parts, which can significantly
> affect the choking impedance and where the chokes are tuned. The work I
> did in 2017 and 2018 included characterizing nearly 200 #31 cores
> obtained from multiple vendors over about ten years, selecting cores at
> the limits of those tolerances, winding and measuring hundreds of chokes
> on those cores, tabulating the results, and making recommendations for
> each band and each transmission line type based on worst case results
> for each design. Chokes wound following the new 2018 Cookbook should
> provide at least the specified response on any #31 core you buy. Note
> that #31 mix is made ONLY by Fair-Rite.
>
> Another point about measuring common mode current. As you have observed,
> it varies along the line, simply because in the common mode circuit, the
> feedline is part of the antenna, and both voltage and current vary along
> the line conforming to wavelength relationships at the operating
> frequency. A good choke forces a current minimum at the point where it
> is inserted. How common mode current varies along the line depends on
> the quality of the choke, the electrical length of the outer conductor
> of the coax (VF~0.98), and how the shield is terminated on the other end
> (grounded or floating using a link coupled tuner).
>
> A choke is most useful at the antenna feedpoint (up in the air, or at
> the feed end of a vertical or other long wire), which tends to minimize
> common mode current all along the line, because it "disconnects" the
> feedline from the antenna. A choke at any other point is FAR less
> effective -- all it does force a current minimum at the point it is
> inserted, leaving the feedline connected to the antenna, allowing common
> mode current between the choke and the antenna, and coupling any noise
> current to the antenna.
>
> For this reason, the first choke in any system should ALWAYS be at the
> antenna IF the antenna is matched to the feedline. The power handling of
> my chokes are ONLY applicable if the feedline is matched at the point
> where they are inserted. A choke inserted into a poorly matched or
> un-matched line is much more likely to overheat and fail. Dissipation
> (heating) is addressed in the 2018 Cookbook.
>
> 73, Jim K9YC
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K8TE

Re: KPA-1500 SWR fault above 700-800 watts on 160m

In reply to this post by Roy Koeppe

That is not true, except at full power. The manual clearly states power
levels at 10:1, 5:1, and 4:1 VSWR's for different frequency ranges.

RTFM is a wonderful acronym to follow. I'm always surprised to read "I
think..." "I recall..." and similar posts to answer a poster's question.
Most of us are U.S.A. males, no offense to those who aren't. As such, our
DNA has been irradiated by past (not Cycle 24) solar cycles and we no long
see the need to read manuals.

A friend of mine bought an IC-7300 because he could operate it without
reading the manual. He has since read some of the manual and uses features
that make his signal (usually weak with a 12 ft. high antenna) more
copyable. I am working on his further conversion.

May the mask be with you! (COVID-19)

73, Bill, K8TE

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Rick Bates, NK7I

Re: KPA-1500 SWR fault above 700-800 watts on 160m

Being able to use a <fill in the blank> without reading the manual is
actually one of my personal tests of the user interface. Jump in, see
how it plays and what is presented to make changes if needed.

The K3 easily passes that test (former Kenwood user; Elecraft is similar
in format), HOWEVER that is on the surface only. One must read through
the manual (a few times preferably) to get into the menu settings (only
one layer deep) and the reasons for them, when to apply them. An annual
or topical review can be done in personal down time, to keep the meat
memory cells active. And even then, something new may 'appear' in the
text and learning happens.

Then for reading dessert, read the firmware update statements as a few
things are added and others change slightly over time since the manual
was created.

I also have a 7300 (for the RV) and it's not as UI friendly to me but is
a convoluted series of menus to alter what should be a simple change; so
it's what one is used to seeing, in part. Some of that is
cross-cultural phrasing, some of it, is a lesser UI (in my opinion).

73,
Rick NK7I

K3, P3, KAT500, KPA500, KPA1500, investments in quality.

On 9/3/2020 11:56 AM, K8TE wrote:

> RTFM is a wonderful acronym to follow. I'm always surprised to read "I
> think..." "I recall..." and similar posts to answer a poster's question.
> Most of us are U.S.A. males, no offense to those who aren't. As such, our
> DNA has been irradiated by past (not Cycle 24) solar cycles and we no long
> see the need to read manuals.
>
> A friend of mine bought an IC-7300 because he could operate it without
> reading the manual. He has since read some of the manual and uses features
> that make his signal (usually weak with a 12 ft. high antenna) more
> copyable. I am working on his further conversion.
>

Josh Fiden

Re: K3 vs Icom UI (was: KPA-1500 SWR fault above 700-800 watts on 160m)

I have a 9700 and since it looks nearly identical to 7300 assume the UI is similar. Intuitive? Not at all. K3 has lots of buried items but they are easy to find and mostly set once & forget. Only gripe would be all the abbreviations, but that was obviously limited by a practical display choice for it’s vintage.

Improved UI with the big display is near the top of items that interest me about K4.

73
Josh W6XU

Sent from my iPad

> On Sep 3, 2020, at 12:23 PM, Rick Bates, NK7I <[hidden email]> wrote:
>
> I also have a 7300 (for the RV) and it's not as UI friendly to me but is a convoluted series of menus to alter what should be a simple change; so it's what one is used to seeing, in part.

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K8TE

Re: KPA-1500 SWR fault above 700-800 watts on 160m

In reply to this post by Rick Bates, NK7I

I do the same Rick. However, when new firmware comes out, I update my
manuals appropriately. Elecraft allows that, unlike Icom, Kenwood, or
Yaesu. I wonder why?

Refreshing my own "firmware" is much more challenging, especially for things
not refreshed by use. Many questions on this reflector are already answered
in the Elecraft manuals.

Watching my P3, I find many, many SSB signals over-driven with, I'll bet,
ALC way out of range, even on an occasional Elecraft rig. When I send them
a screenshot, or mention it on-the-air, frequently, the operator can't find
the ALC reading. RTFM!

I'm hoping the lightning stays away (for a change) during this weekend's QSO
parties. 73, Bill, K8TE

--
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Vic Rosenthal

Re: KPA-1500 SWR fault above 700-800 watts on 160m

In reply to this post by Jim Brown-10

I had an interesting experience trying to use a balun in a very
demanding situation. I'll describe it, and at the end I have a question.

Antenna was a dipole with total length of 10m fed with approximately 480
ohm open-wire line. Line length was 10m. I was trying to use this
antenna on 40m with a power of 1200w.

The first attempt was to use a 5kw DX Engineering 1:4 balun in the shack
between the open line and coax, feeding the coax with an unbalanced
T-network tuner. There was a lot of RFI with computers, etc. in the
shack. The antenna seemed to pick up a lot of local noise. During a
period of contest operating, the balun overheated, causing soaring SWR
and ultimately internal arcing.

Next I added two capacitors in series with the line to tune out the
reactance (the 1/4 wavelength line inverted the capacitive reactance at
the feedpoint of the antenna making it inductive at the shack end). This
eliminated the overheating (it ran a little warm), but the RFI problem
remained.

Then I rewired the balun to a 1:1 configuration. This seemed to help a
little with the RFI. It made tuning easier. But the antenna was still noisy.

At this point I had some really good luck and was able to purchase an
old Johnson KW Matchbox, which is a link-coupled balanced tuner. I
replaced the T-network tuner, the balun, and the series capacitors with
this unit. The antenna is now MUCH quieter and RFI problems have been
eliminated.

The lesson I learned is that baluns don't work very well with high SWR,
especially when the impedance is very reactive.

And now for my question: did I permanently damage my balun when it
overheated? If so, what is the mechanism of damage? I took it apart and
didn't see any obvious signs.

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
.
On 03/09/2020 19:05, Jim Brown wrote:
> <snip> A choke inserted into a poorly
> matched or un-matched line is much more likely to overheat and fail.
> Dissipation (heating) is addressed in the 2018 Cookbook.
>
> 73, Jim K9YC
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Jim Miller

Re: KPA-1500 SWR fault above 700-800 watts on 160m

I’ve seen no mention of modeling and/or measurements performed on any of these antennas to see if they are within the match range of the KPA1500.

Jim ab3cv

On Sep 4, 2020, at 2:29 AM, Victor Rosenthal 4X6GP <[hidden email]> wrote:

I had an interesting experience trying to use a balun in a very demanding situation. I'll describe it, and at the end I have a question.

Antenna was a dipole with total length of 10m fed with approximately 480 ohm open-wire line. Line length was 10m. I was trying to use this antenna on 40m with a power of 1200w.

The first attempt was to use a 5kw DX Engineering 1:4 balun in the shack between the open line and coax, feeding the coax with an unbalanced T-network tuner. There was a lot of RFI with computers, etc. in the shack. The antenna seemed to pick up a lot of local noise. During a period of contest operating, the balun overheated, causing soaring SWR and ultimately internal arcing.

Next I added two capacitors in series with the line to tune out the reactance (the 1/4 wavelength line inverted the capacitive reactance at the feedpoint of the antenna making it inductive at the shack end). This eliminated the overheating (it ran a little warm), but the RFI problem remained.

Then I rewired the balun to a 1:1 configuration. This seemed to help a little with the RFI. It made tuning easier. But the antenna was still noisy.

At this point I had some really good luck and was able to purchase an old Johnson KW Matchbox, which is a link-coupled balanced tuner. I replaced the T-network tuner, the balun, and the series capacitors with this unit. The antenna is now MUCH quieter and RFI problems have been eliminated.

The lesson I learned is that baluns don't work very well with high SWR, especially when the impedance is very reactive.

And now for my question: did I permanently damage my balun when it overheated? If so, what is the mechanism of damage? I took it apart and didn't see any obvious signs.

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
.
> On 03/09/2020 19:05, Jim Brown wrote:
> <snip> A choke inserted into a poorly
> matched or un-matched line is much more likely to overheat and fail.
> Dissipation (heating) is addressed in the 2018 Cookbook.
> 73, Jim K9YC
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