Elecraft

K3/KPA500/KAT500 SWR problem

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Ray Coles

K3/KPA500/KAT500 SWR problem

Forgot to mention that I hauled my MFJ wattmeter/dummy load out to the bush and pushed up 100 watts into it down the feeder with 1:1 SWR, which convinced me that at least my UR8 feeder is OK. Also didn't mention I hooked up my FG01 antenna analyser up at the shack and all seemed normal, but of course the problem only comes over 40 watts (which equates to a pre balun 500V). THE PROBLEM REMAINS and I am still mystified!
73

Sent from my iPhone
Ray Coles CEng M0XDL
10 Littlemoor Road,
Weymouth DT3 6AA
United Kingdom
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KD8NNU

Re: K3/KPA500/KAT500 SWR problem

Interesting as I had a similar problem with my unit on 160m this weekend.

Turned out as I went higher in power I was burning thru an insulator on my
vertical. Thus my problem occurred at higher power until my insulator was
totally gone. Then it was easy to find.

I suspect that that something has arced and now there is a shorting path
that shows up as you go up in power and the KAT500 finds it.

Note I do not use a KPA500 but a different type of amp. I also was able to
watch the swr climb slowly with my W2 as it was slowly starting the
destruction cycle but with lower power the swr was steady. However after
the damage was complete even my antenna analyzer showed the problem. It
took me a bit of time to find the damage before I finally had it nailed
down.

So even though stuff visually looks good and is fine at lower power the coax
could be damaged internally and you are not finding it with the dummy load
as it does not react the same as the antenna because the swr is good.

Just a thought.

~73
Don
KD8NNU
-.- -.. ---.. -. -. ..-
-----Original Message-----
From: Ray Coles
Sent: Monday, December 30, 2013 2:13 PM
To: [hidden email]
Subject: [Elecraft] K3/KPA500/KAT500 SWR problem

Forgot to mention that I hauled my MFJ wattmeter/dummy load out to the bush
and pushed up 100 watts into it down the feeder with 1:1 SWR, which
convinced me that at least my UR8 feeder is OK. Also didn't mention I hooked
up my FG01 antenna analyser up at the shack and all seemed normal, but of
course the problem only comes over 40 watts (which equates to a pre balun
500V). THE PROBLEM REMAINS and I am still mystified!
73

Sent from my iPhone
Ray Coles CEng M0XDL
10 Littlemoor Road,
Weymouth DT3 6AA
United Kingdom
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Jack Brindle-2

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Ray Coles

That’s actually not a valid test. Try it at 500 watts and see what happens. We get away with many things at low power that show up as real problems when the power is increased. Bad connections, coax and components that are not rated for higher power (baluns tend to be a big one here), and sometime antenna parts that are just too close to their surroundings. Watch for include tight bends in the coax (especially in warm climates). As antennas age, things tend to change, components age and start to break down.

Remember, with a non-resonant antenna you can have very high mismatches, shown as high SWR, which results in high voltages and currents in the feed line going back to the tuner. At high power this will age the feed line and components very fast, causing breakdowns. Instead of small coax, try using large stuff, of the RG-8 size (only better). It will still see the high voltages, but is better suited to handle them.

Perhaps a better solution is to use open-wire feedline from the antenna to a point very close to the shack (or inside), then use ashore coax feed and balun between the ATU and feedline. This should work much better, since the open-wire feed is better suited for handling high SWR with very low loss.

Jack Brindle, W6FB

On Dec 30, 2013, at 11:13 AM, Ray Coles <[hidden email]> wrote:

> Forgot to mention that I hauled my MFJ wattmeter/dummy load out to the bush and pushed up 100 watts into it down the feeder with 1:1 SWR, which convinced me that at least my UR8 feeder is OK. Also didn't mention I hooked up my FG01 antenna analyser up at the shack and all seemed normal, but of course the problem only comes over 40 watts (which equates to a pre balun 500V). THE PROBLEM REMAINS and I am still mystified!
> 73
>
> Sent from my iPhone
> Ray Coles CEng M0XDL
> 10 Littlemoor Road,
> Weymouth DT3 6AA
> United Kingdom
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Don Wilhelm-4

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Ray Coles

Ray,

Is that 500 volts RMS or 500 volts peak? Coax, connectors, baluns,
insulators, etc. are usually rated for the peak voltage they will
tolerate without breakdown.

If you calculated that voltage derived from the power and Ohm's Law, you
would have Volts RMS and you may have something breaking down due to
excessive voltage (and that create problems like you are seeing).

73,
Don W3FPR

On 12/30/2013 2:44 PM, Walter Underwood wrote:

> UHF connectors are rated for 500V. Maybe you need N connectors, which can handle 1500V.
>
> wunder
> K6WRU
>
> On Dec 30, 2013, at 11:13 AM, Ray Coles <[hidden email]> wrote:
>
>> Forgot to mention that I hauled my MFJ wattmeter/dummy load out to the bush and pushed up 100 watts into it down the feeder with 1:1 SWR, which convinced me that at least my UR8 feeder is OK. Also didn't mention I hooked up my FG01 antenna analyser up at the shack and all seemed normal, but of course the problem only comes over 40 watts (which equates to a pre balun 500V). THE PROBLEM REMAINS and I am still mystified!
>> 73
>>
>> Sent from my iPhone
>> Ray Coles CEng M0XDL
>> 10 Littlemoor Road,
>> Weymouth DT3 6AA
>> United Kingdom
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
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>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> --
> Walter Underwood
> [hidden email]
>
>
>
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Buck - k4ia

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Ray Coles

I had a similar issue. Drove me crazy. Then one day I put my hand on
the PL259 on my antenna switch and noticed it was warm. Swapped out the
90 degree connector on the coax and problem solved. The high power from
the amp must have been causing a fault in the connector.

Lesson 1. Check all your connections.
Lesson 2. Stop buying cheap coax connectors

Buck
k4ia

On 12/30/2013 2:13 PM, Ray Coles wrote:

k6dgw

Re: K3/KPA500/KAT500 SWR problem

On 12/30/2013 12:48 PM, Buck - k4ia wrote:
> I had a similar issue. Drove me crazy. Then one day I put my hand on
> the PL259 on my antenna switch and noticed it was warm. Swapped out the
> 90 degree connector on the coax and problem solved. The high power from
> the amp must have been causing a fault in the connector.
>
> Lesson 1. Check all your connections.
> Lesson 2. Stop buying cheap coax connectors

Yep. The only ones I've been using are Amphenol with the silver
plating. The solder well, and I've had no problems since I gave up on
the "offshore" ones at RS.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

"The problem with Lessons Learned is that they rarely are."
Leo Endres, philosopher/engineer/colleague

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K5SM

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Ray Coles

FWIW, Although I don't have the KAT500, I have found my KPA500 to be
very, very sensitive to rf on the feedline, especially on 80 and 40
meters. I have checked, rechecked everything (connectors, feedline,
switches, etc.) and tried adding various common mode filters, changing
feedline length, etc. over a period of 2 years now and still have not
resolved the issue. I disassembled my KPA500 and checked all the chassis
grounds, making sure all was tight and no paint was interfering with the
rf integrity of the case. That did produce some improvement, but the
problem persists. In my case, the random swr spike and (occasional)
resulting fault always occur during the first microseconds of a
transmission. Though Elecraft support has worked with me to try to
resolve this issue, so far it has no yielded to our efforts. This does
not occur when I transmit into a dummy load, either in the shack or at
the tower. Though my experience isn't the same as is being discussed
here, I suspect the root cause may be similar.

Bob K5SM

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wayne burdick

Re: K3/KPA500/KAT500 SWR problem

Administrator

We believe this situation can be remediated in firmware. We're gathering information and digging into it.

73,
Wayne
N6kR

On Dec 30, 2013, at 1:42 PM, Robert Redmon <[hidden email]> wrote:

>
> FWIW, Although I don't have the KAT500, I have found my KPA500 to be very, very sensitive to rf on the feedline, especially on 80 and 40 meters. I have checked, rechecked everything (connectors, feedline, switches, etc.) and tried adding various common mode filters, changing feedline length, etc. over a period of 2 years now and still have not resolved the issue. I disassembled my KPA500 and checked all the chassis grounds, making sure all was tight and no paint was interfering with the rf integrity of the case. That did produce some improvement, but the problem persists. In my case, the random swr spike and (occasional) resulting fault always occur during the first microseconds of a transmission. Though Elecraft support has worked with me to try to resolve this issue, so far it has no yielded to our efforts. This does not occur when I transmit into a dummy load, either in the shack or at the tower. Though my experience isn't the same as is being discussed here, I suspect
the root cause may be similar.

>
> Bob K5SM
>
>
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Don Wilhelm-4

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Buck - k4ia

Things like that will show up at medium to higher power levels even
though all looks well at lower power.
Common mode RF voltage getting into the shack will also cause similar
behavior.
Ninety percent of those type problems are solved in the antenna field -
tight good quality connections, good coax and adequate common mode
chokes installed at the right places will usually fix it.

Note also that a good ground system in the shack is usually *not* a good
RF Ground and thinking it to be an RF ground will lead to a lot of
confusion and false moves. For instance, an RF Ground (point of zero RF
voltage crossing) is found at the center of a dipole's center insulator
or between the base of a vertical and a ground plane. The job of a
current choke (or balun) is to constrain the feedline to equal and
opposite currents between the conductors so the RF ground point as well
as RF voltage sources stay where they belong. I digress, but a ground
rod does not make an RF Ground no matter how it is connected. It may
actually be a high impedance for RF - consider a wire to that ground rod
of 8 feet - that will have a high impedance on 10 meters just because it
is a 1/4 wavelength connected to earth (a low impedance point).

73,
Don W3FPR

On 12/30/2013 3:48 PM, Buck - k4ia wrote:

> I had a similar issue. Drove me crazy. Then one day I put my hand on
> the PL259 on my antenna switch and noticed it was warm. Swapped out
> the 90 degree connector on the coax and problem solved. The high
> power from the amp must have been causing a fault in the connector.
>
> Lesson 1. Check all your connections.
> Lesson 2. Stop buying cheap coax connectors
>
> Buck
> k4ia

Bill K9YEQ

Re: K3/KPA500/KAT500 SWR problem

Good points, Don. As a KAT500 FT'er, I used an extensive external grounding
system. I also use a large loop, a 75 dipole and multi band shortened
dipole as well. Generally I have little to no issues. One can "get by"
while on QRP, with significant losses on improperly installed antenna
systems, but once the power goes, esp., QRO, the problems are "amplified"
(pun intended)! I am also very careful when making a large frequency
excursion to start a lowered power tune, despite memory tuning, just to give
a lower power tune rather than full power.

73,
Bill
K9YEQ

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Wilhelm
Sent: Monday, December 30, 2013 4:26 PM
To: [hidden email]
Subject: Re: [Elecraft] K3/KPA500/KAT500 SWR problem

Things like that will show up at medium to higher power levels even though
all looks well at lower power.
Common mode RF voltage getting into the shack will also cause similar
behavior.
Ninety percent of those type problems are solved in the antenna field -
tight good quality connections, good coax and adequate common mode chokes
installed at the right places will usually fix it.

Note also that a good ground system in the shack is usually *not* a good RF
Ground and thinking it to be an RF ground will lead to a lot of confusion
and false moves. For instance, an RF Ground (point of zero RF voltage
crossing) is found at the center of a dipole's center insulator or between
the base of a vertical and a ground plane. The job of a current choke (or
balun) is to constrain the feedline to equal and opposite currents between
the conductors so the RF ground point as well as RF voltage sources stay
where they belong. I digress, but a ground rod does not make an RF Ground
no matter how it is connected. It may actually be a high impedance for RF -
consider a wire to that ground rod of 8 feet - that will have a high
impedance on 10 meters just because it is a 1/4 wavelength connected to
earth (a low impedance point).

73,
Don W3FPR

On 12/30/2013 3:48 PM, Buck - k4ia wrote:

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Bill-3

Re: K3/KPA500/KAT500 SWR problem

There is a lot of mention regarding common mode chokes, RF grounding,
copper to aluminum connections, etc. Speaking only of my station, I
experienced no similar automatic tuner problems with equipment other
than the KAT500. I suspect other ops have similar experiences.

My typical experience using the tuner is QSY - a two second TUNE - and
the KAT knows where and what to do. Everything is just fine - until in
the middle of the QSO the tuner goes berserk and does a retune (a little
noisy). If I talk through it - all will go back to normal in a few
seconds. Disconcerting to say the least.

I do not know if this problem is damaging to the KAP500 and/or the
KPA500. Hence, I am back to running 100 Watts until this is corrected -
changing some coax connections and using the K3's internal tuner. Thus
removing the devices from the lineup.

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wayne burdick

Re: K3/KPA500/KAT500 SWR problem

Administrator

This is correctable in firmware (we're looking into how best to achieve that).

It is extremely unlikely any damage would occur. Both the KAT500 and KPA500 monitor a half-dozen parameters and go into bypass immediately if operation is unsafe.

Wayne
N6KR

On Dec 30, 2013, at 4:38 PM, Bill W2BLC <[hidden email]> wrote:

> There is a lot of mention regarding common mode chokes, RF grounding, copper to aluminum connections, etc. Speaking only of my station, I experienced no similar automatic tuner problems with equipment other than the KAT500. I suspect other ops have similar experiences.
>
> My typical experience using the tuner is QSY - a two second TUNE - and the KAT knows where and what to do. Everything is just fine - until in the middle of the QSO the tuner goes berserk and does a retune (a little noisy). If I talk through it - all will go back to normal in a few seconds. Disconcerting to say the least.
>
> I do not know if this problem is damaging to the KAP500 and/or the KPA500. Hence, I am back to running 100 Watts until this is corrected - changing some coax connections and using the K3's internal tuner. Thus removing the devices from the lineup.
>
> ______________________________________________________________
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Dr. William J. Schmidt, II

Re: K3/KPA500/KAT500 SWR problem

Well mine sure didn't go into bypass...lots of thick black smoke and it
thought everything was just fine/ good to go...as I was running for the fire
extinguisher. It confused the heck out of me because the swr was well below
2:1 (like 1.4:1) and I was well within power limits on CW. The good news is
that it still works... even baked.

Dr. William J. Schmidt - K9HZ / J68HZ/ 8P6HK/ ZF2HZ/ PJ4HZ

Owner - Operator
Big Signal Ranch
Staunton, Illinois

email: [hidden email]

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Monday, December 30, 2013 8:42 PM
To: Bill W2BLC
Cc: [hidden email]
Subject: Re: [Elecraft] K3/KPA500/KAT500 SWR problem

This is correctable in firmware (we're looking into how best to achieve
that).

It is extremely unlikely any damage would occur. Both the KAT500 and KPA500
monitor a half-dozen parameters and go into bypass immediately if operation
is unsafe.

Wayne2
N6KR

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wayne burdick

Re: K3/KPA500/KAT500 SWR problem

Administrator

Your symptoms may be completely unrelated to the discussion at hand (SWR-related faults). Please contact customer support and describe what happened.

73,
Wayne
N6KR

On Dec 30, 2013, at 6:45 PM, "Dr. William J. Schmidt, II" <[hidden email]> wrote:

> Well mine sure didn't go into bypass...lots of thick black smoke and it
> thought everything was just fine/ good to go...as I was running for the fire
> extinguisher. It confused the heck out of me because the swr was well below
> 2:1 (like 1.4:1) and I was well within power limits on CW. The good news is
> that it still works... even baked.
>
>
> Dr. William J. Schmidt - K9HZ / J68HZ/ 8P6HK/ ZF2HZ/ PJ4HZ
>
> Owner - Operator
> Big Signal Ranch
> Staunton, Illinois
>
> email: [hidden email]
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Wayne Burdick
> Sent: Monday, December 30, 2013 8:42 PM
> To: Bill W2BLC
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3/KPA500/KAT500 SWR problem
>
> This is correctable in firmware (we're looking into how best to achieve
> that).
>
> It is extremely unlikely any damage would occur. Both the KAT500 and KPA500
> monitor a half-dozen parameters and go into bypass immediately if operation
> is unsafe.
>
> Wayne2
> N6KR
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Charlie T, K3ICH

Who had an LP-Pan for sale?

In reply to this post by Ray Coles

I'm trying to find the person who listed an lp-pan 2 panadapter for sale.

If it's still available, I would like to purchase it.

I must have deleted the original message.

73, Charlie k3ICH

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ab2tc

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Bill-3

Hi,

Are you in AUTO mode when this is happening? I found it wise to switch to manual mode when finishing the quick tune after a QSY. Before I got into that habit this was happening a number of times. I am running barefoot with no internal tuner in the K3 so those are not a factor. The MFJ tuner I was using before I got the KAT500 also had this problem so it's not unique to the KAT500. For the MFJ I ran a wire out to the remotely located tuner connected to the TUNE button so I could run it in manual (really semiautomatic) mode.

AB2TC - Knut

Bill W2BLC wrote

There is a lot of mention regarding common mode chokes, RF grounding,
copper to aluminum connections, etc. Speaking only of my station, I
experienced no similar automatic tuner problems with equipment other
than the KAT500. I suspect other ops have similar experiences.

My typical experience using the tuner is QSY - a two second TUNE - and
the KAT knows where and what to do. Everything is just fine - until in
the middle of the QSO the tuner goes berserk and does a retune (a little
noisy). If I talk through it - all will go back to normal in a few
seconds. Disconcerting to say the least.

I do not know if this problem is damaging to the KAP500 and/or the
KPA500. Hence, I am back to running 100 Watts until this is corrected -
changing some coax connections and using the K3's internal tuner. Thus
removing the devices from the lineup.

______________________________________________________________
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shfoster

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Ray Coles

Just a thought, how about posting what firmware revision you have in the
KAT500 and or KPA500 when you post about this "problem".
Steve WB5OMP

--
If you forward or copy this message, please delete any reference to my
email address. Thanks
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Dave-8

Re: K3/KPA500/KAT500 SWR Problem

In reply to this post by Ray Coles

I've experienced the same issues others are reporting with the KAT500. The problem is somewhat intermittent. However, it seemed to happen more frequently after going to the 1.41 firmware. After reading one of Dick's posts, I checked the Fault Table just to see what it had in it. I'm seeing the following event logged numerous times.

03 - VFWD above relay hotswitch limit F 50376 VFWD 1411 VRFL 9 VSWR 1.08 VSWRB 2.74

It there some way to "decode" this?

73,
Dave N8AG
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Dick Dievendorff-4

Re: K3/KPA500/KAT500 SWR Problem

Yes. You were transmitting on 50.376 MHz. The forward power was measured at
1411, which is a bit north of 300 watts.

It appears that the amplifier key line is not being interrupted by the
KAT500. We can hot switch KAT500 relays at up to 100 watts, but not higher.

73 de Dick, K6KR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Tuesday, December 31, 2013 10:34 AM
To: [hidden email]
Subject: Re: [Elecraft] K3/KPA500/KAT500 SWR Problem

I've experienced the same issues others are reporting with the KAT500. The
problem is somewhat intermittent. However, it seemed to happen more
frequently after going to the 1.41 firmware. After reading one of Dick's
posts, I checked the Fault Table just to see what it had in it. I'm seeing
the following event logged numerous times.

03 - VFWD above relay hotswitch limit F 50376 VFWD 1411 VRFL 9 VSWR 1.08
VSWRB 2.74

It there some way to "decode" this?

73,
Dave N8AG
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Jeffrey Otterson

Re: K3/KPA500/KAT500 SWR problem

In reply to this post by Ray Coles

I reported this problem to support back in February, and though my question
was responded to, it was never really answered -- I've been living with the
problem since.., I'm sure support can look at the case, it was around
February 7 of this year.

Before I switched to KPA500/KAT500, I was running 12-1400 watts PEP from a
SB-220 through a Drake MN-2700 tuner, with never an issue, so I don't think
the problem is arcing connectors, balun, coax, antennas. Also the raw VSWR
on my 75M antenna is about 2:1, maybe a bit better. (The K3 says 2:1, the
LP-100A, 1.98:1), so I don't think the problem is brought on by excessive
SWR...

Jeff
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