Elecraft

Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

Classic

List

Threaded

58 messages Options

123

Peter W2IRT

Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

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

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

______________________________________________________________
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]

Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Peter W2IRT

Re: NOT the feedline

In reply to this post by Adrian-3

The balun (1:1 current choke here) is a red herring.

If you follow this thread all the way back, you'll see that the previous
antenna was not balun fed, and it used a length of 75 ohm cable and stubs to
match. And in this case the balun is made by InnovAntennas, specifically for
this antenna (also of their design in the UK). If changing any one or two
components had made a significant difference I would have noted it.

First was the antenna change. When that failed to show a marked difference
then I replaced the feedline. Again, no change whatsoever. It's behaving the
same today as it has since I first got on 6m with high power. So either the
amp has an issue or it's something incredibly esoteric that will take a
miracle to find and fix.

I have tried going through an antenna switch and switching via the KPA-1500.
No difference. All coax connectors are genuine Amphenol 83-SP1 and assembled
correctly. New LMR-400 coax, purchased last year and stored inside over the
winter, and new(ish) RG-213 patch cable inside the house. I don't ever reuse
connectors or outdoor coax. Everything I'm seeing is pointing to the fault
being inside the KPA-1500 at this point.

- pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Adrian
Sent: Monday, June 1, 2020 10:13 AM
To: Alan - G4GNX <[hidden email]>; Elecraft Reflector
<[hidden email]>
Subject: Re: [Elecraft] NOT the feedline

If you use a decent combination balun such as ;
https://www.balundesigns.com/model-4116-4-1-hybrid-balun-1-5-54mhz-3kw/
if you have any metal structure in range of the field, or

https://www.balundesigns.com/model-4115ocf-4-1-for-ocf-dipoles-1-5-54-mhz-5k
w/
for a total current 4:1 balun. These are very robust at high power, and no
other feedpoint RF common mode choke is required.

I ran a K3 , amp and ocf dipole like this, with above balun earlier this
decade with great success, had top 4a4a dxpedition total band vk points with
this one antenna. Also the windom and ocf are different animals.

The true windom uses the vertical section of its feedline as part of the
antenna, such that any ocf dipole with a feedpoint common mode choke cannot
be referred to as a 'windom'

Adrian Fewster

On 1/6/20 11:45 pm, Alan - G4GNX wrote:

______________________________________________________________
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]

Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Adrian-3

Re: NOT the feedline

In that case, then it should also fault with a 50 ohm dummy load under
the same settings.

Does it ?

Adrian Fewster

Everything I'm seeing is pointing to the fault

> being inside the KPA-1500 at this point.
>
> - pjd
>
______________________________________________________________
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: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

In reply to this post by Stephen Shearer

On 6/1/2020 6:37 AM, stephen shearer wrote:
> Ground loops can be another issue.
> I was having a "feed back" issue with my KX3/KXPA100 ans solved it
> eliminating ground/power loops.

DANGER, WILL ROBINSON!

First, ain't no such thing as a "ground loop." The real cause of
problems we BLAME on this fictional condition is failure to do proper
bonding within our stations and all other "grounds" in our homes.

BY LAW (Electrical Building Codes, usually a version of NEC or based on
NEC), ALL grounds in any facility must be bonded together. At a minimum,
all equipment plugged into the wall must have its chassis bonded to the
green wire in its power cord.

In a ham station, every chassis must be directly bonded to the others by
short, fat copper, AND all equipment that will be interconnected with
the station (rig, computer, audio interface) should get AC power from
outlets that share the same green wire back to the breaker panel.

Lots of detail on this in http://k9yc.com/GroundingAndAudio.pdf and in
N0AX's ARRL book on the topic, on which we collaborated.

73, Jim K9YC

______________________________________________________________
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]

Ned Mountain WC4X

Re: NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

In reply to this post by Peter W2IRT

I had a similar issue with my K3s/KPA 1500 that defied logic. Without going
into all the details, I finally sent both the K3s and KPA 1500 back to
Elecraft to have them analyze it as a systems problem. It turned out to be
a faulty 100W PA on the K3s that would generate very short high level
transient pulses that somehow caused the fault. Since having that replaced
all has been extremely stable for over 12 months.

This problem always happened on 6 meters, sometimes on 10 meters, but never
on any lower frequencies.

Best of luck.

Ned
WC4X

--
Sent from: http://elecraft.365791.n2.nabble.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]

Bob McGraw - K4TAX

Re: NOT the feedline

In reply to this post by Alan - G4GNX

Based on my experience, balun power ratings are for MATCHED conditions.
It is rare that hams use a balun in a matched condition.    Thus a 1:1
balun should see 50 ohms on the input and 50 ohms on the output, while a
4:1 balun should see 200 ohms on the output and 50 ohms on the input.
In the case of a resonant folded dipole, a 4:1 balun is typically
operating in a nearly matched condition.    All others combinations are
unknown and random.

I run about 500 watts on all bands. My baluns are rated at 5KW!   It
takes 3 or 4 big hunkin' pieces of ferrite to attain this power level.
My 6 meter balun is a 1/2 wavelength electrically of RG-213. No ferrite!

Buy or build a balun of your choice. Using an IR temperature gun,
measure the ambient temperature of the core. Run about 1/2 rated power
carrier for 30 to 60 seconds. Measure the temperature again.   If it is
warm to hot, this is RF producing heat.   And likely continuing will
produce core failure.   This is not a good balun for your application.

One of my baluns work between the output of my KAT500 and the balanced
feed line connected to the center of a 256 ft wire. That antenna works
160M - 6M with zero issues.   Now, I do run a hybrid balun being a 4:1
Guanella balun as a transformer, and it is fed with a 1:1 balun for
common mode rejection.

Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are not
at all a proper balun design A Guanella balun will have 2 cores with 2
windings and then another 2 separate cores with another 2 windings.
These are then wired to produce a 4:1 balun with good common mode
rejection.    Most "factory" 4:1 baluns are poorly designed and built junk.

See https://www.dj0ip.de/balun-stuff/ for further references.

73

Bob, K4TAX

On 6/1/2020 8:45 AM, Alan - G4GNX wrote:

> I have a similar issue with ferrite 'balun' heating, although mostly
> tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
> balun at the feed point, but also has a sleeve 'balun' consisting of 8
> ferrites wrapped in a plastic sleeve, about 3 feet from the feed
> point. If I run the K3S at 100W, via the KPA500 in standby, then
> through the KAT500 tuner, I see no problems.
>
> On increasing the power to 200W by using the KPA500 in Operate and
> about 10W drive from the K3S, during a SSB 'over' the temperature of
> the KPA500 rises and after a few minutes, the SWR readings on the
> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
> very kindly went through my fault log and came to the conclusion that
> the fault is with the antenna/feeder and I agree with him. What is
> strange is that if I leave a solid carrier running at 200W, I can't
> easily reproduce the issue and I wonder if its something being
> affected by peak excursions with SSB?
>
> When things do start to go wrong, I can usually perform a manual tune
> with the KAT500 and the fault will then not (mostly) be apparent.
>
> Anyway, I'm in the process of replacing the entire feeder with
> Westflex 103 and much bigger ferrites. I will also replace the main
> balun which is a 400W device for a 1KW device, as I think that running
> the UK max of 400W may be pushing the spec of a 400W balun. Also, the
> balun itself or connections to it may be faulty.
>
> The point now is that I have discovered some damage to the outer
> covering of the sleeve 'balun' which may be the result of ferrites
> overheating or may be the cause of movement of the ferrites thus
> causing instability. Either way, heftier devices seem to be the order
> of the day.
>
> Although the KPA500 temperature rise is somewhat expected, I feel it's
> a bit higher over a short period than I would like and may be due to
> reflected power.
>
> 73,
>
> Alan. G4GNX
>
>
> ------ Original Message ------
> From: "David Olean" <[hidden email]>
> To: "Peter Dougherty" <[hidden email]>
> Cc: [hidden email]
> Sent: 01/06/2020 13:25:18
> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m;
> SWR issues)
>
>> Hello Peter
>>
>> I suspect RFI as well. I do not have a KPA1500, so my advice is not
>> worth much, but the fact that the fault only occurs when a signal is
>> being radiated sends me a red flag. I had a similar problem here
>> with my SPE amplifier power output. I was measuring it on an LP-100A
>> wattmeter. It turns out that 1.8 MHz energy from the SPE amp
>> radiated from my vertical antenna and was getting into a new wire
>> doublet antenna and coming back down the ladder line into the shack.
>> The ladder line was about 7 inches from the power coupler for the
>> LP-100A. RF caused the readings to go wacky and it looked like my
>> amplifier was going postal! The problem was high rf fields next to
>> the power meter coupler.
>>
>> Ferrite balun heating can be seen with a VSWR meter if you set the
>> power at some intermediate level, key the amp up with a steady
>> carrier, and watch for VSWR creeping up. Loose pins in coax can also
>> be a problem. They can heat up and disconnect or start arcing. Those
>> problems do not typically show VSWR creep. They happen all at once
>> usually.
>>
>> The KPA1500 works fine into a dummy load. (No RFI) That is a big
>> clue. Good luck and I hope you find the problem. Maybe an RF
>> sniffer would detect the ingress point?
>>
>> 73
>>
>> Dave K1WHS
>>
>
> ______________________________________________________________
> 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]

Peter W2IRT

Re: NOT the feedline

Your point is valid, however the underlying fact in my situation is that the new antenna with the new 1:1 current balun (i.e. feedline choke) is presenting **identically** to my old antenna that didn't have a balun. Neither better nor worse.

- pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Bob McGraw K4TAX
Sent: Monday, June 1, 2020 4:48 PM
To: [hidden email]
Subject: Re: [Elecraft] NOT the feedline

Based on my experience, balun power ratings are for MATCHED conditions. It is rare that hams use a balun in a matched condition. Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the output, while a
4:1 balun should see 200 ohms on the output and 50 ohms on the input. In the case of a resonant folded dipole, a 4:1 balun is typically operating in a nearly matched condition. All others combinations are unknown and random.

I run about 500 watts on all bands. My baluns are rated at 5KW! It takes 3 or 4 big hunkin' pieces of ferrite to attain this power level. My 6 meter balun is a 1/2 wavelength electrically of RG-213. No ferrite!

Buy or build a balun of your choice. Using an IR temperature gun, measure the ambient temperature of the core. Run about 1/2 rated power carrier for 30 to 60 seconds. Measure the temperature again. If it is warm to hot, this is RF producing heat. And likely continuing will produce core failure. This is not a good balun for your application.

One of my baluns work between the output of my KAT500 and the balanced feed line connected to the center of a 256 ft wire. That antenna works 160M - 6M with zero issues. Now, I do run a hybrid balun being a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun for common mode rejection.

Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are not at all a proper balun design A Guanella balun will have 2 cores with 2 windings and then another 2 separate cores with another 2 windings. These are then wired to produce a 4:1 balun with good common mode rejection. Most "factory" 4:1 baluns are poorly designed and built junk.

See https://www.dj0ip.de/balun-stuff/ for further references.

73

Bob, K4TAX

On 6/1/2020 8:45 AM, Alan - G4GNX wrote:

> I have a similar issue with ferrite 'balun' heating, although mostly
> tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
> balun at the feed point, but also has a sleeve 'balun' consisting of 8
> ferrites wrapped in a plastic sleeve, about 3 feet from the feed
> point. If I run the K3S at 100W, via the KPA500 in standby, then
> through the KAT500 tuner, I see no problems.
>
> On increasing the power to 200W by using the KPA500 in Operate and
> about 10W drive from the K3S, during a SSB 'over' the temperature of
> the KPA500 rises and after a few minutes, the SWR readings on the
> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
> very kindly went through my fault log and came to the conclusion that
> the fault is with the antenna/feeder and I agree with him. What is
> strange is that if I leave a solid carrier running at 200W, I can't
> easily reproduce the issue and I wonder if its something being
> affected by peak excursions with SSB?
>
> When things do start to go wrong, I can usually perform a manual tune
> with the KAT500 and the fault will then not (mostly) be apparent.
>
> Anyway, I'm in the process of replacing the entire feeder with
> Westflex 103 and much bigger ferrites. I will also replace the main
> balun which is a 400W device for a 1KW device, as I think that running
> the UK max of 400W may be pushing the spec of a 400W balun. Also, the
> balun itself or connections to it may be faulty.
>
> The point now is that I have discovered some damage to the outer
> covering of the sleeve 'balun' which may be the result of ferrites
> overheating or may be the cause of movement of the ferrites thus
> causing instability. Either way, heftier devices seem to be the order
> of the day.
>
> Although the KPA500 temperature rise is somewhat expected, I feel it's
> a bit higher over a short period than I would like and may be due to
> reflected power.
>
> 73,
>
> Alan. G4GNX
>
>
> ------ Original Message ------
> From: "David Olean" <[hidden email]>
> To: "Peter Dougherty" <[hidden email]>
> Cc: [hidden email]
> Sent: 01/06/2020 13:25:18
> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m;
> SWR issues)
>
>> Hello Peter
>>
>> I suspect RFI as well. I do not have a KPA1500, so my advice is not
>> worth much, but the fact that the fault only occurs when a signal is
>> being radiated sends me a red flag. I had a similar problem here
>> with my SPE amplifier power output. I was measuring it on an LP-100A
>> wattmeter. It turns out that 1.8 MHz energy from the SPE amp
>> radiated from my vertical antenna and was getting into a new wire
>> doublet antenna and coming back down the ladder line into the shack.
>> The ladder line was about 7 inches from the power coupler for the
>> LP-100A. RF caused the readings to go wacky and it looked like my
>> amplifier was going postal! The problem was high rf fields next to
>> the power meter coupler.
>>
>> Ferrite balun heating can be seen with a VSWR meter if you set the
>> power at some intermediate level, key the amp up with a steady
>> carrier, and watch for VSWR creeping up. Loose pins in coax can also
>> be a problem. They can heat up and disconnect or start arcing. Those
>> problems do not typically show VSWR creep. They happen all at once
>> usually.
>>
>> The KPA1500 works fine into a dummy load. (No RFI) That is a big
>> clue. Good luck and I hope you find the problem. Maybe an RF
>> sniffer would detect the ingress point?
>>
>> 73
>>
>> Dave K1WHS
>>
>
> ______________________________________________________________
> 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]

______________________________________________________________
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]

Lovin' my K3S (S/N 10023)
73, Peter W2IRT

k6dgw

Re: NOT the feedline

In reply to this post by Bob McGraw - K4TAX

Nearly same experience Bob: Sloping V, 135 ft legs, from top of 80 ft
tower fed with homemade 600 ohm open wire using a DX Engineering 4:1
"balun" [a strange, usually misunderstood piece of electronic apparatus
often used for the wrong reasons] rated at 10 KW. It warmed up
noticeably at 1.2 KW RTTY use. It helps to remember that one can
saturate a ferrite core [especially when very hot] which creates a
racket reminiscent of a non-synchronous spark gap TX.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 6/1/2020 1:48 PM, Bob McGraw K4TAX wrote:

> Based on my experience, balun power ratings are for MATCHED
> conditions. It is rare that hams use a balun in a matched condition.
>    Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the
> output, while a 4:1 balun should see 200 ohms on the output and 50
> ohms on the input.   In the case of a resonant folded dipole, a 4:1
> balun is typically operating in a nearly matched condition. All others
> combinations are unknown and random.
>
> I run about 500 watts on all bands. My baluns are rated at 5KW! It
> takes 3 or 4 big hunkin' pieces of ferrite to attain this power
> level.   My 6 meter balun is a 1/2 wavelength electrically of RG-213.
> No ferrite!
>
> Buy or build a balun of your choice. Using an IR temperature gun,
> measure the ambient temperature of the core. Run about 1/2 rated
> power carrier for 30 to 60 seconds. Measure the temperature again.
> If it is warm to hot, this is RF producing heat.   And likely
> continuing will produce core failure.   This is not a good balun for
> your application.
>
> One of my baluns work between the output of my KAT500 and the balanced
> feed line connected to the center of a 256 ft wire. That antenna
> works 160M - 6M with zero issues.   Now, I do run a hybrid balun being
> a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun
> for common mode rejection.
>
> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are
> not at all a proper balun design A Guanella balun will have 2 cores
> with 2 windings and then another 2 separate cores with another 2
> windings. These are then wired to produce a 4:1 balun with good
> common mode rejection.    Most "factory" 4:1 baluns are poorly
> designed and built junk.
>
> See https://www.dj0ip.de/balun-stuff/ for further references.
>
> 73
>
> Bob, K4TAX

Ted Edwards W3TB

Re: NOT the feedline

I am following this with great interest.
Like Alan G0GNX, I also use an OCF, RG-8X out to the current balun in this
case, 300 ohm to the antenna. K3, KPA-500 and KAT-500.

If I am running stations in a contest on 40m and also 80m CW, It "appears"
that my VSWR rises after a half hour and then the KAT-500 starts to try to
spontaneously retune. Doesn't happen on 20m and up. This past weekend in
CQ WPX, I reduced drive so that output was about 300 watts and it all
became tame.

I had thought that it was a heating of the RG-8X; then I changed my mind to
the current balun from Radiowavz that is rated for 1.5 KW. I think it is
the balun just getting hot out there. I had used a W2AU 4:1 balun with my
OCF, which is a voltage balun but I didn't know about that -- for upwards
of 40 years and with the Elecraft equipment for about 4 years since I got
the amp/tuner. I just switched to a current balun last year with one that
I bought at Dayton.

I would have expected more problem with the voltage balun than with the
current balun. I could change back to the W2AU if needed.

Interesting stuff, so I am reading along. And my thanks to all of you.

On Mon, Jun 1, 2020 at 4:42 PM Fred Jensen <[hidden email]> wrote:

> Nearly same experience Bob: Sloping V, 135 ft legs, from top of 80 ft
> tower fed with homemade 600 ohm open wire using a DX Engineering 4:1
> "balun" [a strange, usually misunderstood piece of electronic apparatus
> often used for the wrong reasons] rated at 10 KW. It warmed up
> noticeably at 1.2 KW RTTY use. It helps to remember that one can
> saturate a ferrite core [especially when very hot] which creates a
> racket reminiscent of a non-synchronous spark gap TX.
>
> 73,
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
> On 6/1/2020 1:48 PM, Bob McGraw K4TAX wrote:
> > Based on my experience, balun power ratings are for MATCHED
> > conditions. It is rare that hams use a balun in a matched condition.
> > Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the
> > output, while a 4:1 balun should see 200 ohms on the output and 50
> > ohms on the input. In the case of a resonant folded dipole, a 4:1
> > balun is typically operating in a nearly matched condition. All others
> > combinations are unknown and random.
> >
> > I run about 500 watts on all bands. My baluns are rated at 5KW! It
> > takes 3 or 4 big hunkin' pieces of ferrite to attain this power
> > level. My 6 meter balun is a 1/2 wavelength electrically of RG-213.
> > No ferrite!
> >
> > Buy or build a balun of your choice. Using an IR temperature gun,
> > measure the ambient temperature of the core. Run about 1/2 rated
> > power carrier for 30 to 60 seconds. Measure the temperature again.
> > If it is warm to hot, this is RF producing heat. And likely
> > continuing will produce core failure. This is not a good balun for
> > your application.
> >
> > One of my baluns work between the output of my KAT500 and the balanced
> > feed line connected to the center of a 256 ft wire. That antenna
> > works 160M - 6M with zero issues. Now, I do run a hybrid balun being
> > a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun
> > for common mode rejection.
> >
> > Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are
> > not at all a proper balun design A Guanella balun will have 2 cores
> > with 2 windings and then another 2 separate cores with another 2
> > windings. These are then wired to produce a 4:1 balun with good
> > common mode rejection. Most "factory" 4:1 baluns are poorly
> > designed and built junk.
> >
> > See https://www.dj0ip.de/balun-stuff/ for further references.
> >
> > 73
> >
> > Bob, K4TAX
>
> ______________________________________________________________
> 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]

--
73 de Ted Edwards, W3TB and GØPWW

and thinking about operating CW:
"Do today what others won't,
so you can do tomorrow what others can't."
______________________________________________________________
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

Re: NOT the feedline

In reply to this post by Peter W2IRT

Lets take another try at this. There still isn’t enough information in your emails to really determine what might be going on. From the amplifier’s viewpoint, *everything* from the antenna jack on the back of the amplifier is part of the antenna system. So far we know it consists of some section of RG213, another of LM400, a balun of some sort, and an antenna. There are undoubtedly some adapters and couplers in between, and perhaps a few other things. Knowing exactly what these are is critical in making any suggestions.

Every few months since we released the KPA500 we have seen emails from folks who are certain that the amplifier is causing a problem. We all build our stations for low power, then decide that adding an amplifier is needed, so we buy one. We then are faced with issues driving a lot more power into the antenna system. These are caused by deficiencies in that system, which was sized for much lower power, and almost always will contain at least one component that cannot handle the power. The last part of the KPA500 before power goes out is the directional coupler (note: it is after the low pass filters), the KPA1500 has its ATU after those components. With the KPA1500 ATU in bypass, the directional coupler becomes the last component. This is important because the directional coupler will see any problem in the antenna system, and report it. No amplifier component is in the way to modify things, we get a true picture of what follows the amplifier. So, when something glitches in the antenna system (usually an arc in a coupler, or an overheated toroid in a balun or matching unit), the directional coupler picks it up and moves to protect the amplifier.

With this in mind, place the KPA1500 ATU into bypass and perform the test. When you see the fault occur, you then need to look at the entire antenna system, starting at the antenna jack on the back of the KPA1500. All of the components are suspect, even a new part (balun, antenna, etc), which may have been affected by high power right after installation. Be sure to looks at the RG213, and at the coupler to the LM400. You have made reference to shack feed-through, what is that, and does it use components that might have issues?

As in past cases, find the problem in the overall antenna system, and the KPA1500 will be much happier, as will you.

So, before we can help you, we need to know the details of the system.

73!
Jack, W6FB
Elecraft Engineering

> On Jun 1, 2020, at 2:25 PM, Peter Dougherty <[hidden email]> wrote:
>
> Your point is valid, however the underlying fact in my situation is that the new antenna with the new 1:1 current balun (i.e. feedline choke) is presenting **identically** to my old antenna that didn't have a balun. Neither better nor worse.
>
> - pjd
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On Behalf Of Bob McGraw K4TAX
> Sent: Monday, June 1, 2020 4:48 PM
> To: [hidden email]
> Subject: Re: [Elecraft] NOT the feedline
>
> Based on my experience, balun power ratings are for MATCHED conditions. It is rare that hams use a balun in a matched condition. Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the output, while a
> 4:1 balun should see 200 ohms on the output and 50 ohms on the input. In the case of a resonant folded dipole, a 4:1 balun is typically operating in a nearly matched condition. All others combinations are unknown and random.
>
> I run about 500 watts on all bands. My baluns are rated at 5KW! It takes 3 or 4 big hunkin' pieces of ferrite to attain this power level. My 6 meter balun is a 1/2 wavelength electrically of RG-213. No ferrite!
>
> Buy or build a balun of your choice. Using an IR temperature gun, measure the ambient temperature of the core. Run about 1/2 rated power carrier for 30 to 60 seconds. Measure the temperature again. If it is warm to hot, this is RF producing heat. And likely continuing will produce core failure. This is not a good balun for your application.
>
> One of my baluns work between the output of my KAT500 and the balanced feed line connected to the center of a 256 ft wire. That antenna works 160M - 6M with zero issues. Now, I do run a hybrid balun being a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun for common mode rejection.
>
> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are not at all a proper balun design A Guanella balun will have 2 cores with 2 windings and then another 2 separate cores with another 2 windings. These are then wired to produce a 4:1 balun with good common mode rejection. Most "factory" 4:1 baluns are poorly designed and built junk.
>
> See https://www.dj0ip.de/balun-stuff/ for further references.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 8:45 AM, Alan - G4GNX wrote:
>> I have a similar issue with ferrite 'balun' heating, although mostly
>> tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
>> balun at the feed point, but also has a sleeve 'balun' consisting of 8
>> ferrites wrapped in a plastic sleeve, about 3 feet from the feed
>> point. If I run the K3S at 100W, via the KPA500 in standby, then
>> through the KAT500 tuner, I see no problems.
>>
>> On increasing the power to 200W by using the KPA500 in Operate and
>> about 10W drive from the K3S, during a SSB 'over' the temperature of
>> the KPA500 rises and after a few minutes, the SWR readings on the
>> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
>> very kindly went through my fault log and came to the conclusion that
>> the fault is with the antenna/feeder and I agree with him. What is
>> strange is that if I leave a solid carrier running at 200W, I can't
>> easily reproduce the issue and I wonder if its something being
>> affected by peak excursions with SSB?
>>
>> When things do start to go wrong, I can usually perform a manual tune
>> with the KAT500 and the fault will then not (mostly) be apparent.
>>
>> Anyway, I'm in the process of replacing the entire feeder with
>> Westflex 103 and much bigger ferrites. I will also replace the main
>> balun which is a 400W device for a 1KW device, as I think that running
>> the UK max of 400W may be pushing the spec of a 400W balun. Also, the
>> balun itself or connections to it may be faulty.
>>
>> The point now is that I have discovered some damage to the outer
>> covering of the sleeve 'balun' which may be the result of ferrites
>> overheating or may be the cause of movement of the ferrites thus
>> causing instability. Either way, heftier devices seem to be the order
>> of the day.
>>
>> Although the KPA500 temperature rise is somewhat expected, I feel it's
>> a bit higher over a short period than I would like and may be due to
>> reflected power.
>>
>> 73,
>>
>> Alan. G4GNX
>>
>>
>> ------ Original Message ------
>> From: "David Olean" <[hidden email]>
>> To: "Peter Dougherty" <[hidden email]>
>> Cc: [hidden email]
>> Sent: 01/06/2020 13:25:18
>> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m;
>> SWR issues)
>>
>>> Hello Peter
>>>
>>> I suspect RFI as well. I do not have a KPA1500, so my advice is not
>>> worth much, but the fact that the fault only occurs when a signal is
>>> being radiated sends me a red flag. I had a similar problem here
>>> with my SPE amplifier power output. I was measuring it on an LP-100A
>>> wattmeter. It turns out that 1.8 MHz energy from the SPE amp
>>> radiated from my vertical antenna and was getting into a new wire
>>> doublet antenna and coming back down the ladder line into the shack.
>>> The ladder line was about 7 inches from the power coupler for the
>>> LP-100A. RF caused the readings to go wacky and it looked like my
>>> amplifier was going postal! The problem was high rf fields next to
>>> the power meter coupler.
>>>
>>> Ferrite balun heating can be seen with a VSWR meter if you set the
>>> power at some intermediate level, key the amp up with a steady
>>> carrier, and watch for VSWR creeping up. Loose pins in coax can also
>>> be a problem. They can heat up and disconnect or start arcing. Those
>>> problems do not typically show VSWR creep. They happen all at once
>>> usually.
>>>
>>> The KPA1500 works fine into a dummy load. (No RFI) That is a big
>>> clue. Good luck and I hope you find the problem. Maybe an RF
>>> sniffer would detect the ingress point?
>>>
>>> 73
>>>
>>> Dave K1WHS
>>>
>>
>> ______________________________________________________________
>> 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]
>
> ______________________________________________________________
> 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]

Kidder, George

Re: NOT the feedline

In reply to this post by Ted Edwards W3TB

One of my antennas is a commercial "G5RV" fed with 33' of 450 ohm ladder
line, terminated in a PL-259 pair, with coax from there to the shack.
Apparently this combination results in very high RF voltage at the
PL-259, and it arcs over at 1000 W (not from an Elecraft amp!). This
combo goes wild when I attempt high power on 80M, although it is stable
at 100 W. Just another thing to watch out for!

73 - George, W3HBM

On 6/1/2020 5:59 PM, Ted Edwards W3TB wrote:

> [This message came from an external source. If suspicious, report to [hidden email]<mailto:[hidden email]>]
>
> I am following this with great interest.
> Like Alan G0GNX, I also use an OCF, RG-8X out to the current balun in this
> case, 300 ohm to the antenna. K3, KPA-500 and KAT-500.
>
> If I am running stations in a contest on 40m and also 80m CW, It "appears"
> that my VSWR rises after a half hour and then the KAT-500 starts to try to
> spontaneously retune. Doesn't happen on 20m and up. This past weekend in
> CQ WPX, I reduced drive so that output was about 300 watts and it all
> became tame.
>
> I had thought that it was a heating of the RG-8X; then I changed my mind to
> the current balun from Radiowavz that is rated for 1.5 KW. I think it is
> the balun just getting hot out there. I had used a W2AU 4:1 balun with my
> OCF, which is a voltage balun but I didn't know about that -- for upwards
> of 40 years and with the Elecraft equipment for about 4 years since I got
> the amp/tuner. I just switched to a current balun last year with one that
> I bought at Dayton.
>
> I would have expected more problem with the voltage balun than with the
> current balun. I could change back to the W2AU if needed.
>
> Interesting stuff, so I am reading along. And my thanks to all of you.
>
> On Mon, Jun 1, 2020 at 4:42 PM Fred Jensen <[hidden email]> wrote:
>
>> Nearly same experience Bob: Sloping V, 135 ft legs, from top of 80 ft
>> tower fed with homemade 600 ohm open wire using a DX Engineering 4:1
>> "balun" [a strange, usually misunderstood piece of electronic apparatus
>> often used for the wrong reasons] rated at 10 KW. It warmed up
>> noticeably at 1.2 KW RTTY use. It helps to remember that one can
>> saturate a ferrite core [especially when very hot] which creates a
>> racket reminiscent of a non-synchronous spark gap TX.
>>
>> 73,
>> Fred ["Skip"] K6DGW
>> Sparks NV DM09dn
>> Washoe County
>>
>> On 6/1/2020 1:48 PM, Bob McGraw K4TAX wrote:
>>> Based on my experience, balun power ratings are for MATCHED
>>> conditions. It is rare that hams use a balun in a matched condition.
>>> Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the
>>> output, while a 4:1 balun should see 200 ohms on the output and 50
>>> ohms on the input. In the case of a resonant folded dipole, a 4:1
>>> balun is typically operating in a nearly matched condition. All others
>>> combinations are unknown and random.
>>>
>>> I run about 500 watts on all bands. My baluns are rated at 5KW! It
>>> takes 3 or 4 big hunkin' pieces of ferrite to attain this power
>>> level. My 6 meter balun is a 1/2 wavelength electrically of RG-213.
>>> No ferrite!
>>>
>>> Buy or build a balun of your choice. Using an IR temperature gun,
>>> measure the ambient temperature of the core. Run about 1/2 rated
>>> power carrier for 30 to 60 seconds. Measure the temperature again.
>>> If it is warm to hot, this is RF producing heat. And likely
>>> continuing will produce core failure. This is not a good balun for
>>> your application.
>>>
>>> One of my baluns work between the output of my KAT500 and the balanced
>>> feed line connected to the center of a 256 ft wire. That antenna
>>> works 160M - 6M with zero issues. Now, I do run a hybrid balun being
>>> a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun
>>> for common mode rejection.
>>>
>>> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are
>>> not at all a proper balun design A Guanella balun will have 2 cores
>>> with 2 windings and then another 2 separate cores with another 2
>>> windings. These are then wired to produce a 4:1 balun with good
>>> common mode rejection. Most "factory" 4:1 baluns are poorly
>>> designed and built junk.
>>>
>>> See https://www.dj0ip.de/balun-stuff/ for further references.
>>>
>>> 73
>>>
>>> Bob, K4TAX
>> ______________________________________________________________
>> 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]
>
>
> --
> 73 de Ted Edwards, W3TB and GØPWW
>
> and thinking about operating CW:
> "Do today what others won't,
> so you can do tomorrow what others can't."
> ______________________________________________________________
> 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]

NK7Z

Re: NOT the feedline

In reply to this post by k6dgw

Is it possible that Common mode is getting into the amp, and forcing a
fault?

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 6/1/20 2:40 PM, Fred Jensen wrote:

> Nearly same experience Bob: Sloping V, 135 ft legs, from top of 80 ft
> tower fed with homemade 600 ohm open wire using a DX Engineering 4:1
> "balun" [a strange, usually misunderstood piece of electronic apparatus
> often used for the wrong reasons] rated at 10 KW. It warmed up
> noticeably at 1.2 KW RTTY use. It helps to remember that one can
> saturate a ferrite core [especially when very hot] which creates a
> racket reminiscent of a non-synchronous spark gap TX.
>
> 73,
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
> On 6/1/2020 1:48 PM, Bob McGraw K4TAX wrote:
>> Based on my experience, balun power ratings are for MATCHED
>> conditions. It is rare that hams use a balun in a matched condition.
>>    Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the
>> output, while a 4:1 balun should see 200 ohms on the output and 50
>> ohms on the input.   In the case of a resonant folded dipole, a 4:1
>> balun is typically operating in a nearly matched condition. All others
>> combinations are unknown and random.
>>
>> I run about 500 watts on all bands. My baluns are rated at 5KW! It
>> takes 3 or 4 big hunkin' pieces of ferrite to attain this power
>> level.   My 6 meter balun is a 1/2 wavelength electrically of RG-213.
>> No ferrite!
>>
>> Buy or build a balun of your choice. Using an IR temperature gun,
>> measure the ambient temperature of the core. Run about 1/2 rated
>> power carrier for 30 to 60 seconds. Measure the temperature again. If
>> it is warm to hot, this is RF producing heat.   And likely continuing
>> will produce core failure.   This is not a good balun for your
>> application.
>>
>> One of my baluns work between the output of my KAT500 and the balanced
>> feed line connected to the center of a 256 ft wire. That antenna
>> works 160M - 6M with zero issues.   Now, I do run a hybrid balun being
>> a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun
>> for common mode rejection.
>>
>> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are
>> not at all a proper balun design A Guanella balun will have 2 cores
>> with 2 windings and then another 2 separate cores with another 2
>> windings. These are then wired to produce a 4:1 balun with good
>> common mode rejection.    Most "factory" 4:1 baluns are poorly
>> designed and built junk.
>>
>> See https://www.dj0ip.de/balun-stuff/ for further references.
>>
>> 73
>>
>> Bob, K4TAX
>
> ______________________________________________________________
> 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]

David Gilbert-2

Re: NOT the feedline

I had an antenna for 160m that had a fairly high SWR at the feedpoint, but
was easy to match to 50 ohms with a series inductor less than 30 feet
further down the line toward the shack. I put a common mode choke per
K9YC's designs at the antenna feedpoint, though, and even though it was
actually two chokes in series (two large cores with separate windings) that
should easily handle 5 KW under matched conditions, at 1.5 KW it heated up
in less than two seconds to put the QRO Tech HF-2500DX amp into a fault. I
could have moved the choke to the shack side of the matching inductor, but
I decided it was best to just fix the antenna. No problems after I did.

Common mode chokes don't need high saturation current to get hot (and
that's rarely the problem anyway) ... high SWR voltages work just fine for
that. And at high power it can happen in a very brief period of time.

Everyone stay safe,
Dave AB7E

>
______________________________________________________________
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]

Ted Edwards W3TB

Re: NOT the feedline

Back to Bob K4TAX
I had a common mode current problem when I lived in Virginia and ran 100
watts barefoot, and it came as I could not do a significant angle away from
the antenna --- which I eventually solved.

I really do love the OCF idea. Through modeling it and patterns and then
careful selection of trees for directionality, I have been able to land the
lobes on Europe, South America, and East Asia for 40m, 20m, and 15m with
upwards of 8 dBi --- not too shabby for a wire antenna.

I have some LMR-400 and RG-9 B/U here and plan to change out the coax. I
no longer expect that work to solve the issue, so I am looking at baluns.
While it is a change back from a current balun to voltage balun, I must may
do it.

Thanks for all the good wisdom, guys!

On Mon, Jun 1, 2020 at 6:33 PM David Gilbert <[hidden email]> wrote:

> I had an antenna for 160m that had a fairly high SWR at the feedpoint, but
> was easy to match to 50 ohms with a series inductor less than 30 feet
> further down the line toward the shack. I put a common mode choke per
> K9YC's designs at the antenna feedpoint, though, and even though it was
> actually two chokes in series (two large cores with separate windings) that
> should easily handle 5 KW under matched conditions, at 1.5 KW it heated up
> in less than two seconds to put the QRO Tech HF-2500DX amp into a fault. I
> could have moved the choke to the shack side of the matching inductor, but
> I decided it was best to just fix the antenna. No problems after I did.
>
> Common mode chokes don't need high saturation current to get hot (and
> that's rarely the problem anyway) ... high SWR voltages work just fine for
> that. And at high power it can happen in a very brief period of time.
>
> Everyone stay safe,
> Dave AB7E
>
>
> >
> ______________________________________________________________
> 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]
>

Peter W2IRT

Re: NOT the feedline

In reply to this post by Elecraft mailing list

Thanks for the reply, Jack.

Here's a FULL summary of what is in the line at this moment from the jack on up.

PL-259 (soldered, Amphenol 83-1SP as all are) to about 2 feet of RG-213 feeding into a Ten-Tec Tuner, which is being used only as an antenna switch and is in bypass. This is needed because the power supply fan noise on the KPA-1500 is just so overwhelming that I can only power it on when needed. I am primarily an HF operator, so ANT-1 is reserved for my HF stack. If I put the 6m antenna on ANT-2, I would need to keep the amp running. So everything goes out on ANT-1, through the TT-238. From there, one feedline goes to the HF stack and the other to the 6m output. It gets SLIGHTLY better if I go directly from the KPA-1500 to the input box, as follows but I still experience faults.

From there, a PL-259, and 7 or 8 feet of RG-213. Another PL-259, an Amphenol barrel connector in the input box, PL259, then approximately 65 or 70 feet of Commscope-branded LMR-400. PL-259 from that is connected to an Amphenol SO-239 female-to-N-Male, the choke balun, then the driven loop element to the antenna.

As of Tuesday morning this will change as follows. KPA-1500 ANT-1 out, PL-259 and about 40' of Davis BuryFlex out to the remote antenna switch at the base of the HF stack. From there, about 25 more feet of BuryFlex, a barrel connector then the LMR-400 up to the 6m antenna. This will basically just be an experiment to see if there's any improvement; I'll be bypassing both the old Ten-Tec tuner/switch and the inlet box, and routing via the HF signal path and automatic antenna switch. Adding 65' of BuryFlex to the path strikes me as adding measurable and fairly significant loss to an otherwise really good, quiet antenna system, but if it lets me operate without having to worry about hard faults all the time then I'll take that as a tradeoff.

- pjd

-----Original Message-----
From: Jack Brindle <[hidden email]>
Sent: Monday, June 1, 2020 6:09 PM
To: Peter Dougherty <[hidden email]>
Cc: Bob McGraw K4TAX <[hidden email]>; [hidden email]
Subject: Re: [Elecraft] NOT the feedline

Lets take another try at this. There still isn’t enough information in your emails to really determine what might be going on. From the amplifier’s viewpoint, *everything* from the antenna jack on the back of the amplifier is part of the antenna system. So far we know it consists of some section of RG213, another of LM400, a balun of some sort, and an antenna. There are undoubtedly some adapters and couplers in between, and perhaps a few other things. Knowing exactly what these are is critical in making any suggestions.

Every few months since we released the KPA500 we have seen emails from folks who are certain that the amplifier is causing a problem. We all build our stations for low power, then decide that adding an amplifier is needed, so we buy one. We then are faced with issues driving a lot more power into the antenna system. These are caused by deficiencies in that system, which was sized for much lower power, and almost always will contain at least one component that cannot handle the power. The last part of the KPA500 before power goes out is the directional coupler (note: it is after the low pass filters), the KPA1500 has its ATU after those components. With the KPA1500 ATU in bypass, the directional coupler becomes the last component. This is important because the directional coupler will see any problem in the antenna system, and report it. No amplifier component is in the way to modify things, we get a true picture of what follows the amplifier. So, when something glitches in the antenna system (usually an arc in a coupler, or an overheated toroid in a balun or matching unit), the directional coupler picks it up and moves to protect the amplifier.

With this in mind, place the KPA1500 ATU into bypass and perform the test. When you see the fault occur, you then need to look at the entire antenna system, starting at the antenna jack on the back of the KPA1500. All of the components are suspect, even a new part (balun, antenna, etc), which may have been affected by high power right after installation. Be sure to looks at the RG213, and at the coupler to the LM400. You have made reference to shack feed-through, what is that, and does it use components that might have issues?

As in past cases, find the problem in the overall antenna system, and the KPA1500 will be much happier, as will you.

So, before we can help you, we need to know the details of the system.

73!
Jack, W6FB
Elecraft Engineering

> On Jun 1, 2020, at 2:25 PM, Peter Dougherty <[hidden email]> wrote:
>
> Your point is valid, however the underlying fact in my situation is that the new antenna with the new 1:1 current balun (i.e. feedline choke) is presenting **identically** to my old antenna that didn't have a balun. Neither better nor worse.
>
> - pjd
>
> -----Original Message-----
> From: [hidden email]
> <[hidden email]> On Behalf Of Bob McGraw K4TAX
> Sent: Monday, June 1, 2020 4:48 PM
> To: [hidden email]
> Subject: Re: [Elecraft] NOT the feedline
>
> Based on my experience, balun power ratings are for MATCHED conditions. It is rare that hams use a balun in a matched condition. Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the output, while a
> 4:1 balun should see 200 ohms on the output and 50 ohms on the input. In the case of a resonant folded dipole, a 4:1 balun is typically operating in a nearly matched condition. All others combinations are unknown and random.
>
> I run about 500 watts on all bands. My baluns are rated at 5KW! It takes 3 or 4 big hunkin' pieces of ferrite to attain this power level. My 6 meter balun is a 1/2 wavelength electrically of RG-213. No ferrite!
>
> Buy or build a balun of your choice. Using an IR temperature gun, measure the ambient temperature of the core. Run about 1/2 rated power carrier for 30 to 60 seconds. Measure the temperature again. If it is warm to hot, this is RF producing heat. And likely continuing will produce core failure. This is not a good balun for your application.
>
> One of my baluns work between the output of my KAT500 and the balanced feed line connected to the center of a 256 ft wire. That antenna works 160M - 6M with zero issues. Now, I do run a hybrid balun being a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun for common mode rejection.
>
> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are not at all a proper balun design A Guanella balun will have 2 cores with 2 windings and then another 2 separate cores with another 2 windings. These are then wired to produce a 4:1 balun with good common mode rejection. Most "factory" 4:1 baluns are poorly designed and built junk.
>
> See https://www.dj0ip.de/balun-stuff/ for further references.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 8:45 AM, Alan - G4GNX wrote:
>> I have a similar issue with ferrite 'balun' heating, although mostly
>> tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
>> balun at the feed point, but also has a sleeve 'balun' consisting of
>> 8 ferrites wrapped in a plastic sleeve, about 3 feet from the feed
>> point. If I run the K3S at 100W, via the KPA500 in standby, then
>> through the KAT500 tuner, I see no problems.
>>
>> On increasing the power to 200W by using the KPA500 in Operate and
>> about 10W drive from the K3S, during a SSB 'over' the temperature of
>> the KPA500 rises and after a few minutes, the SWR readings on the
>> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
>> very kindly went through my fault log and came to the conclusion that
>> the fault is with the antenna/feeder and I agree with him. What is
>> strange is that if I leave a solid carrier running at 200W, I can't
>> easily reproduce the issue and I wonder if its something being
>> affected by peak excursions with SSB?
>>
>> When things do start to go wrong, I can usually perform a manual tune
>> with the KAT500 and the fault will then not (mostly) be apparent.
>>
>> Anyway, I'm in the process of replacing the entire feeder with
>> Westflex 103 and much bigger ferrites. I will also replace the main
>> balun which is a 400W device for a 1KW device, as I think that
>> running the UK max of 400W may be pushing the spec of a 400W balun.
>> Also, the balun itself or connections to it may be faulty.
>>
>> The point now is that I have discovered some damage to the outer
>> covering of the sleeve 'balun' which may be the result of ferrites
>> overheating or may be the cause of movement of the ferrites thus
>> causing instability. Either way, heftier devices seem to be the order
>> of the day.
>>
>> Although the KPA500 temperature rise is somewhat expected, I feel
>> it's a bit higher over a short period than I would like and may be
>> due to reflected power.
>>
>> 73,
>>
>> Alan. G4GNX
>>
>>
>> ------ Original Message ------
>> From: "David Olean" <[hidden email]>
>> To: "Peter Dougherty" <[hidden email]>
>> Cc: [hidden email]
>> Sent: 01/06/2020 13:25:18
>> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on
>> 6m; SWR issues)
>>
>>> Hello Peter
>>>
>>> I suspect RFI as well. I do not have a KPA1500, so my advice is not
>>> worth much, but the fact that the fault only occurs when a signal is
>>> being radiated sends me a red flag. I had a similar problem here
>>> with my SPE amplifier power output. I was measuring it on an LP-100A
>>> wattmeter. It turns out that 1.8 MHz energy from the SPE amp
>>> radiated from my vertical antenna and was getting into a new wire
>>> doublet antenna and coming back down the ladder line into the shack.
>>> The ladder line was about 7 inches from the power coupler for the
>>> LP-100A. RF caused the readings to go wacky and it looked like my
>>> amplifier was going postal! The problem was high rf fields next to
>>> the power meter coupler.
>>>
>>> Ferrite balun heating can be seen with a VSWR meter if you set the
>>> power at some intermediate level, key the amp up with a steady
>>> carrier, and watch for VSWR creeping up. Loose pins in coax can
>>> also be a problem. They can heat up and disconnect or start arcing.
>>> Those problems do not typically show VSWR creep. They happen all at
>>> once usually.
>>>
>>> The KPA1500 works fine into a dummy load. (No RFI) That is a big
>>> clue. Good luck and I hope you find the problem. Maybe an RF
>>> sniffer would detect the ingress point?
>>>
>>> 73
>>>
>>> Dave K1WHS
>>>
>>
>> ______________________________________________________________
>> 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]
>
> ______________________________________________________________
> 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]

Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Elecraft mailing list

Re: NOT the feedline

Is it the 3 element 6m LFA? That is an interesting antenna. Which of the baluns did you get? They show three - two for 50 - 70 MHz, and a third for HF and 6m. G0KSC has some interesting designed - I will be waiting to hear your results with this one.

I’ll go through your details here and see what I might come up with. In the mean time I will be interested in the results of your tests tomorrow. Getting info about the TenTec ATU/switch may be difficult, but it wouldn’t surprise me if that is the source. I am sure somewhere in here you will find the problem.

I usually take these problem-solving discussion off-line, but let’s leave this one here because of the already wide interest.

73 and have a great evening!
Jack, W6FB

> On Jun 1, 2020, at 5:47 PM, Peter Dougherty <[hidden email]> wrote:
>
> Thanks for the reply, Jack.
>
> Here's a FULL summary of what is in the line at this moment from the jack on up.
>
> PL-259 (soldered, Amphenol 83-1SP as all are) to about 2 feet of RG-213 feeding into a Ten-Tec Tuner, which is being used only as an antenna switch and is in bypass. This is needed because the power supply fan noise on the KPA-1500 is just so overwhelming that I can only power it on when needed. I am primarily an HF operator, so ANT-1 is reserved for my HF stack. If I put the 6m antenna on ANT-2, I would need to keep the amp running. So everything goes out on ANT-1, through the TT-238. From there, one feedline goes to the HF stack and the other to the 6m output. It gets SLIGHTLY better if I go directly from the KPA-1500 to the input box, as follows but I still experience faults.
>
> From there, a PL-259, and 7 or 8 feet of RG-213. Another PL-259, an Amphenol barrel connector in the input box, PL259, then approximately 65 or 70 feet of Commscope-branded LMR-400. PL-259 from that is connected to an Amphenol SO-239 female-to-N-Male, the choke balun, then the driven loop element to the antenna.
>
> As of Tuesday morning this will change as follows. KPA-1500 ANT-1 out, PL-259 and about 40' of Davis BuryFlex out to the remote antenna switch at the base of the HF stack. From there, about 25 more feet of BuryFlex, a barrel connector then the LMR-400 up to the 6m antenna. This will basically just be an experiment to see if there's any improvement; I'll be bypassing both the old Ten-Tec tuner/switch and the inlet box, and routing via the HF signal path and automatic antenna switch. Adding 65' of BuryFlex to the path strikes me as adding measurable and fairly significant loss to an otherwise really good, quiet antenna system, but if it lets me operate without having to worry about hard faults all the time then I'll take that as a tradeoff.
>
> - pjd
>
> -----Original Message-----
> From: Jack Brindle <[hidden email]>
> Sent: Monday, June 1, 2020 6:09 PM
> To: Peter Dougherty <[hidden email]>
> Cc: Bob McGraw K4TAX <[hidden email]>; [hidden email]
> Subject: Re: [Elecraft] NOT the feedline
>
> Lets take another try at this. There still isn’t enough information in your emails to really determine what might be going on. From the amplifier’s viewpoint, *everything* from the antenna jack on the back of the amplifier is part of the antenna system. So far we know it consists of some section of RG213, another of LM400, a balun of some sort, and an antenna. There are undoubtedly some adapters and couplers in between, and perhaps a few other things. Knowing exactly what these are is critical in making any suggestions.
>
> Every few months since we released the KPA500 we have seen emails from folks who are certain that the amplifier is causing a problem. We all build our stations for low power, then decide that adding an amplifier is needed, so we buy one. We then are faced with issues driving a lot more power into the antenna system. These are caused by deficiencies in that system, which was sized for much lower power, and almost always will contain at least one component that cannot handle the power. The last part of the KPA500 before power goes out is the directional coupler (note: it is after the low pass filters), the KPA1500 has its ATU after those components. With the KPA1500 ATU in bypass, the directional coupler becomes the last component. This is important because the directional coupler will see any problem in the antenna system, and report it. No amplifier component is in the way to modify things, we get a true picture of what follows the amplifier. So, when something glitches in the antenna system (usually an arc in a coupler, or an overheated toroid in a balun or matching unit), the directional coupler picks it up and moves to protect the amplifier.
>
> With this in mind, place the KPA1500 ATU into bypass and perform the test. When you see the fault occur, you then need to look at the entire antenna system, starting at the antenna jack on the back of the KPA1500. All of the components are suspect, even a new part (balun, antenna, etc), which may have been affected by high power right after installation. Be sure to looks at the RG213, and at the coupler to the LM400. You have made reference to shack feed-through, what is that, and does it use components that might have issues?
>
> As in past cases, find the problem in the overall antenna system, and the KPA1500 will be much happier, as will you.
>
> So, before we can help you, we need to know the details of the system.
>
> 73!
> Jack, W6FB
> Elecraft Engineering
>
>
>> On Jun 1, 2020, at 2:25 PM, Peter Dougherty <[hidden email]> wrote:
>>
>> Your point is valid, however the underlying fact in my situation is that the new antenna with the new 1:1 current balun (i.e. feedline choke) is presenting **identically** to my old antenna that didn't have a balun. Neither better nor worse.
>>
>> - pjd
>>
>> -----Original Message-----
>> From: [hidden email]
>> <[hidden email]> On Behalf Of Bob McGraw K4TAX
>> Sent: Monday, June 1, 2020 4:48 PM
>> To: [hidden email]
>> Subject: Re: [Elecraft] NOT the feedline
>>
>> Based on my experience, balun power ratings are for MATCHED conditions. It is rare that hams use a balun in a matched condition. Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the output, while a
>> 4:1 balun should see 200 ohms on the output and 50 ohms on the input. In the case of a resonant folded dipole, a 4:1 balun is typically operating in a nearly matched condition. All others combinations are unknown and random.
>>
>> I run about 500 watts on all bands. My baluns are rated at 5KW! It takes 3 or 4 big hunkin' pieces of ferrite to attain this power level. My 6 meter balun is a 1/2 wavelength electrically of RG-213. No ferrite!
>>
>> Buy or build a balun of your choice. Using an IR temperature gun, measure the ambient temperature of the core. Run about 1/2 rated power carrier for 30 to 60 seconds. Measure the temperature again. If it is warm to hot, this is RF producing heat. And likely continuing will produce core failure. This is not a good balun for your application.
>>
>> One of my baluns work between the output of my KAT500 and the balanced feed line connected to the center of a 256 ft wire. That antenna works 160M - 6M with zero issues. Now, I do run a hybrid balun being a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun for common mode rejection.
>>
>> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are not at all a proper balun design A Guanella balun will have 2 cores with 2 windings and then another 2 separate cores with another 2 windings. These are then wired to produce a 4:1 balun with good common mode rejection. Most "factory" 4:1 baluns are poorly designed and built junk.
>>
>> See https://www.dj0ip.de/balun-stuff/ for further references.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>> On 6/1/2020 8:45 AM, Alan - G4GNX wrote:
>>> I have a similar issue with ferrite 'balun' heating, although mostly
>>> tested on 40 metres. I'm using an OSCFD (Windom) which has a main 4:1
>>> balun at the feed point, but also has a sleeve 'balun' consisting of
>>> 8 ferrites wrapped in a plastic sleeve, about 3 feet from the feed
>>> point. If I run the K3S at 100W, via the KPA500 in standby, then
>>> through the KAT500 tuner, I see no problems.
>>>
>>> On increasing the power to 200W by using the KPA500 in Operate and
>>> about 10W drive from the K3S, during a SSB 'over' the temperature of
>>> the KPA500 rises and after a few minutes, the SWR readings on the
>>> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
>>> very kindly went through my fault log and came to the conclusion that
>>> the fault is with the antenna/feeder and I agree with him. What is
>>> strange is that if I leave a solid carrier running at 200W, I can't
>>> easily reproduce the issue and I wonder if its something being
>>> affected by peak excursions with SSB?
>>>
>>> When things do start to go wrong, I can usually perform a manual tune
>>> with the KAT500 and the fault will then not (mostly) be apparent.
>>>
>>> Anyway, I'm in the process of replacing the entire feeder with
>>> Westflex 103 and much bigger ferrites. I will also replace the main
>>> balun which is a 400W device for a 1KW device, as I think that
>>> running the UK max of 400W may be pushing the spec of a 400W balun.
>>> Also, the balun itself or connections to it may be faulty.
>>>
>>> The point now is that I have discovered some damage to the outer
>>> covering of the sleeve 'balun' which may be the result of ferrites
>>> overheating or may be the cause of movement of the ferrites thus
>>> causing instability. Either way, heftier devices seem to be the order
>>> of the day.
>>>
>>> Although the KPA500 temperature rise is somewhat expected, I feel
>>> it's a bit higher over a short period than I would like and may be
>>> due to reflected power.
>>>
>>> 73,
>>>
>>> Alan. G4GNX
>>>
>>>
>>> ------ Original Message ------
>>> From: "David Olean" <[hidden email]>
>>> To: "Peter Dougherty" <[hidden email]>
>>> Cc: [hidden email]
>>> Sent: 01/06/2020 13:25:18
>>> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on
>>> 6m; SWR issues)
>>>
>>>> Hello Peter
>>>>
>>>> I suspect RFI as well. I do not have a KPA1500, so my advice is not
>>>> worth much, but the fact that the fault only occurs when a signal is
>>>> being radiated sends me a red flag. I had a similar problem here
>>>> with my SPE amplifier power output. I was measuring it on an LP-100A
>>>> wattmeter. It turns out that 1.8 MHz energy from the SPE amp
>>>> radiated from my vertical antenna and was getting into a new wire
>>>> doublet antenna and coming back down the ladder line into the shack.
>>>> The ladder line was about 7 inches from the power coupler for the
>>>> LP-100A. RF caused the readings to go wacky and it looked like my
>>>> amplifier was going postal! The problem was high rf fields next to
>>>> the power meter coupler.
>>>>
>>>> Ferrite balun heating can be seen with a VSWR meter if you set the
>>>> power at some intermediate level, key the amp up with a steady
>>>> carrier, and watch for VSWR creeping up. Loose pins in coax can
>>>> also be a problem. They can heat up and disconnect or start arcing.
>>>> Those problems do not typically show VSWR creep. They happen all at
>>>> once usually.
>>>>
>>>> The KPA1500 works fine into a dummy load. (No RFI) That is a big
>>>> clue. Good luck and I hope you find the problem. Maybe an RF
>>>> sniffer would detect the ingress point?
>>>>
>>>> 73
>>>>
>>>> Dave K1WHS
>>>>
>>>
>>> ______________________________________________________________
>>> 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]
>>
>> ______________________________________________________________
>> 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: NOT the feedline

In reply to this post by Alan - G4GNX

On 6/1/2020 6:45 AM, Alan - G4GNX wrote:

Alan,

What you describe basically a lousy common mode choke, applied to an
antenna that, because it is so badly unbalanced, has a LOT common mode
current. The primary function of such a choke is to prevent common mode
noise picked up on that feedline from coupling to the antenna, and from
there to the receiver. I don't know of a way to EFFECTIVELY choke such
an antenna. The application of ANY choke to such an antenna is an
unnatural act -- it does nothing useful.

I strongly suggest that you study the material on my website about how
common mode chokes work. These concepts have been part of the ARRL
Handbook and/or Antenna Book for nearly 10 years.

k9yc.com/publish.htm

The word "balun" is used to describe nearly a dozen very different
things. What COULD work is a two winding transformer wound on a low loss
ferrite toroid, like Fair-Rite #61 or #67 material. #61 will likely
handle 100W from 160M to 10M without overheating. #67, which has much
lower loss above about 17M, may be required at the 400W level, and would
certainly be used at 1 kW and above.

Making the windings bifilar provides a capacitive path for common mode
current, degrading its effectiveness. This is minimized by placing the
windings on opposite sides of the toroidal core.

73, Jim K9YC
______________________________________________________________
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]

Peter W2IRT

Re: NOT the feedline

In reply to this post by Elecraft mailing list

It's the 6 element LFA on a 6.8 meter boom. The balun is their 50 MHz ferrite core balun.

I want to get the Ten-Tec tuner out of the equation forthwith but unless I can solve the fan noise problems it's a non-starter. My XYL is working from home in the same home-office that my shack is located in, about 6 feet away from my operating desk. The fan noise drives *me* crazy but she won't tolerate it being on all day when I'm just monitoring six. I work enough stuff on CW on HF for it to remain the primary concern, so I can't really put that on ANT-2, which I did try.

Hopefully going through the main antenna switch will help--I'll find out tomorrow.

- pjd

-----Original Message-----
From: Jack Brindle <[hidden email]>
Sent: Monday, June 1, 2020 9:29 PM
To: Peter Dougherty <[hidden email]>
Cc: Elecraft Mailer <[hidden email]>
Subject: Re: [Elecraft] NOT the feedline

Is it the 3 element 6m LFA? That is an interesting antenna. Which of the baluns did you get? They show three - two for 50 - 70 MHz, and a third for HF and 6m. G0KSC has some interesting designed - I will be waiting to hear your results with this one.

I’ll go through your details here and see what I might come up with. In the mean time I will be interested in the results of your tests tomorrow. Getting info about the TenTec ATU/switch may be difficult, but it wouldn’t surprise me if that is the source. I am sure somewhere in here you will find the problem.

I usually take these problem-solving discussion off-line, but let’s leave this one here because of the already wide interest.

73 and have a great evening!
Jack, W6FB

> On Jun 1, 2020, at 5:47 PM, Peter Dougherty <[hidden email]> wrote:
>
> Thanks for the reply, Jack.
>
> Here's a FULL summary of what is in the line at this moment from the jack on up.
>
> PL-259 (soldered, Amphenol 83-1SP as all are) to about 2 feet of RG-213 feeding into a Ten-Tec Tuner, which is being used only as an antenna switch and is in bypass. This is needed because the power supply fan noise on the KPA-1500 is just so overwhelming that I can only power it on when needed. I am primarily an HF operator, so ANT-1 is reserved for my HF stack. If I put the 6m antenna on ANT-2, I would need to keep the amp running. So everything goes out on ANT-1, through the TT-238. From there, one feedline goes to the HF stack and the other to the 6m output. It gets SLIGHTLY better if I go directly from the KPA-1500 to the input box, as follows but I still experience faults.
>
> From there, a PL-259, and 7 or 8 feet of RG-213. Another PL-259, an Amphenol barrel connector in the input box, PL259, then approximately 65 or 70 feet of Commscope-branded LMR-400. PL-259 from that is connected to an Amphenol SO-239 female-to-N-Male, the choke balun, then the driven loop element to the antenna.
>
> As of Tuesday morning this will change as follows. KPA-1500 ANT-1 out, PL-259 and about 40' of Davis BuryFlex out to the remote antenna switch at the base of the HF stack. From there, about 25 more feet of BuryFlex, a barrel connector then the LMR-400 up to the 6m antenna. This will basically just be an experiment to see if there's any improvement; I'll be bypassing both the old Ten-Tec tuner/switch and the inlet box, and routing via the HF signal path and automatic antenna switch. Adding 65' of BuryFlex to the path strikes me as adding measurable and fairly significant loss to an otherwise really good, quiet antenna system, but if it lets me operate without having to worry about hard faults all the time then I'll take that as a tradeoff.
>
> - pjd
>
> -----Original Message-----
> From: Jack Brindle <[hidden email]>
> Sent: Monday, June 1, 2020 6:09 PM
> To: Peter Dougherty <[hidden email]>
> Cc: Bob McGraw K4TAX <[hidden email]>; [hidden email]
> Subject: Re: [Elecraft] NOT the feedline
>
> Lets take another try at this. There still isn’t enough information in your emails to really determine what might be going on. From the amplifier’s viewpoint, *everything* from the antenna jack on the back of the amplifier is part of the antenna system. So far we know it consists of some section of RG213, another of LM400, a balun of some sort, and an antenna. There are undoubtedly some adapters and couplers in between, and perhaps a few other things. Knowing exactly what these are is critical in making any suggestions.
>
> Every few months since we released the KPA500 we have seen emails from folks who are certain that the amplifier is causing a problem. We all build our stations for low power, then decide that adding an amplifier is needed, so we buy one. We then are faced with issues driving a lot more power into the antenna system. These are caused by deficiencies in that system, which was sized for much lower power, and almost always will contain at least one component that cannot handle the power. The last part of the KPA500 before power goes out is the directional coupler (note: it is after the low pass filters), the KPA1500 has its ATU after those components. With the KPA1500 ATU in bypass, the directional coupler becomes the last component. This is important because the directional coupler will see any problem in the antenna system, and report it. No amplifier component is in the way to modify things, we get a true picture of what follows the amplifier. So, when something glitches in the antenna system (usually an arc in a coupler, or an overheated toroid in a balun or matching unit), the directional coupler picks it up and moves to protect the amplifier.
>
> With this in mind, place the KPA1500 ATU into bypass and perform the test. When you see the fault occur, you then need to look at the entire antenna system, starting at the antenna jack on the back of the KPA1500. All of the components are suspect, even a new part (balun, antenna, etc), which may have been affected by high power right after installation. Be sure to looks at the RG213, and at the coupler to the LM400. You have made reference to shack feed-through, what is that, and does it use components that might have issues?
>
> As in past cases, find the problem in the overall antenna system, and the KPA1500 will be much happier, as will you.
>
> So, before we can help you, we need to know the details of the system.
>
> 73!
> Jack, W6FB
> Elecraft Engineering
>
>
>> On Jun 1, 2020, at 2:25 PM, Peter Dougherty <[hidden email]> wrote:
>>
>> Your point is valid, however the underlying fact in my situation is that the new antenna with the new 1:1 current balun (i.e. feedline choke) is presenting **identically** to my old antenna that didn't have a balun. Neither better nor worse.
>>
>> - pjd
>>
>> -----Original Message-----
>> From: [hidden email]
>> <[hidden email]> On Behalf Of Bob McGraw K4TAX
>> Sent: Monday, June 1, 2020 4:48 PM
>> To: [hidden email]
>> Subject: Re: [Elecraft] NOT the feedline
>>
>> Based on my experience, balun power ratings are for MATCHED conditions. It is rare that hams use a balun in a matched condition. Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the output, while a
>> 4:1 balun should see 200 ohms on the output and 50 ohms on the input. In the case of a resonant folded dipole, a 4:1 balun is typically operating in a nearly matched condition. All others combinations are unknown and random.
>>
>> I run about 500 watts on all bands. My baluns are rated at 5KW! It takes 3 or 4 big hunkin' pieces of ferrite to attain this power level. My 6 meter balun is a 1/2 wavelength electrically of RG-213. No ferrite!
>>
>> Buy or build a balun of your choice. Using an IR temperature gun, measure the ambient temperature of the core. Run about 1/2 rated power carrier for 30 to 60 seconds. Measure the temperature again. If it is warm to hot, this is RF producing heat. And likely continuing will produce core failure. This is not a good balun for your application.
>>
>> One of my baluns work between the output of my KAT500 and the balanced feed line connected to the center of a 256 ft wire. That antenna works 160M - 6M with zero issues. Now, I do run a hybrid balun being a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun for common mode rejection.
>>
>> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are not at all a proper balun design A Guanella balun will have 2 cores with 2 windings and then another 2 separate cores with another 2 windings. These are then wired to produce a 4:1 balun with good common mode rejection. Most "factory" 4:1 baluns are poorly designed and built junk.
>>
>> See https://www.dj0ip.de/balun-stuff/ for further references.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>> On 6/1/2020 8:45 AM, Alan - G4GNX wrote:
>>> I have a similar issue with ferrite 'balun' heating, although mostly
>>> tested on 40 metres. I'm using an OSCFD (Windom) which has a main
>>> 4:1 balun at the feed point, but also has a sleeve 'balun'
>>> consisting of
>>> 8 ferrites wrapped in a plastic sleeve, about 3 feet from the feed
>>> point. If I run the K3S at 100W, via the KPA500 in standby, then
>>> through the KAT500 tuner, I see no problems.
>>>
>>> On increasing the power to 200W by using the KPA500 in Operate and
>>> about 10W drive from the K3S, during a SSB 'over' the temperature of
>>> the KPA500 rises and after a few minutes, the SWR readings on the
>>> KPA500 and KAT500 start to rise. One of the Elecraft guys actually
>>> very kindly went through my fault log and came to the conclusion
>>> that the fault is with the antenna/feeder and I agree with him. What
>>> is strange is that if I leave a solid carrier running at 200W, I
>>> can't easily reproduce the issue and I wonder if its something being
>>> affected by peak excursions with SSB?
>>>
>>> When things do start to go wrong, I can usually perform a manual
>>> tune with the KAT500 and the fault will then not (mostly) be apparent.
>>>
>>> Anyway, I'm in the process of replacing the entire feeder with
>>> Westflex 103 and much bigger ferrites. I will also replace the main
>>> balun which is a 400W device for a 1KW device, as I think that
>>> running the UK max of 400W may be pushing the spec of a 400W balun.
>>> Also, the balun itself or connections to it may be faulty.
>>>
>>> The point now is that I have discovered some damage to the outer
>>> covering of the sleeve 'balun' which may be the result of ferrites
>>> overheating or may be the cause of movement of the ferrites thus
>>> causing instability. Either way, heftier devices seem to be the
>>> order of the day.
>>>
>>> Although the KPA500 temperature rise is somewhat expected, I feel
>>> it's a bit higher over a short period than I would like and may be
>>> due to reflected power.
>>>
>>> 73,
>>>
>>> Alan. G4GNX
>>>
>>>
>>> ------ Original Message ------
>>> From: "David Olean" <[hidden email]>
>>> To: "Peter Dougherty" <[hidden email]>
>>> Cc: [hidden email]
>>> Sent: 01/06/2020 13:25:18
>>> Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on
>>> 6m; SWR issues)
>>>
>>>> Hello Peter
>>>>
>>>> I suspect RFI as well. I do not have a KPA1500, so my advice is not
>>>> worth much, but the fact that the fault only occurs when a signal
>>>> is being radiated sends me a red flag. I had a similar problem
>>>> here with my SPE amplifier power output. I was measuring it on an
>>>> LP-100A wattmeter. It turns out that 1.8 MHz energy from the SPE
>>>> amp radiated from my vertical antenna and was getting into a new
>>>> wire doublet antenna and coming back down the ladder line into the shack.
>>>> The ladder line was about 7 inches from the power coupler for the
>>>> LP-100A. RF caused the readings to go wacky and it looked like my
>>>> amplifier was going postal! The problem was high rf fields next to
>>>> the power meter coupler.
>>>>
>>>> Ferrite balun heating can be seen with a VSWR meter if you set the
>>>> power at some intermediate level, key the amp up with a steady
>>>> carrier, and watch for VSWR creeping up. Loose pins in coax can
>>>> also be a problem. They can heat up and disconnect or start arcing.
>>>> Those problems do not typically show VSWR creep. They happen all at
>>>> once usually.
>>>>
>>>> The KPA1500 works fine into a dummy load. (No RFI) That is a big
>>>> clue. Good luck and I hope you find the problem. Maybe an RF
>>>> sniffer would detect the ingress point?
>>>>
>>>> 73
>>>>
>>>> Dave K1WHS
>>>>
>>>
>>> ______________________________________________________________
>>> 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]
>>
>> ______________________________________________________________
>> 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]
>
>

Lovin' my K3S (S/N 10023)
73, Peter W2IRT

Jim Brown-10

Re: NOT the feedline

In reply to this post by Adrian-3

On 6/1/2020 7:13 AM, Adrian wrote:
> If you use a decent combination balun such as ;
> https://www.balundesigns.com/model-4116-4-1-hybrid-balun-1-5-54mhz-3kw/
> if you have any metal structure in range of the field, or

These are probably effective as impedance matching devices, but
everything I've seen from this company indicates they don't have a clue
about how common mode chokes work. Several years ago, a member of our
contest club building a big contest station in the Caribbean gave me one
of their common mode choke "baluns" to measure. It looked NOTHING like
the the curves published on their website, and was a LOUSY choke. It
probably would not have blown up with power, but it certainly wouldn't
have done much to kill common mode noise over the frequency range
advertised.

> The true windom uses the vertical section of its feedline as part of
> the antenna, such that any ocf dipole with a feedpoint common mode
> choke cannot be referred to as a 'windom'

Whatever it's called, while it was probably a very good idea many years
ago when it was conceived, it's a LOUSY idea today because the design is
a sitting duck for the increasingly massive levels of RF noise in our
homes and the homes of our neighbors. As old-timers learned many years
ago, "if you can't hear 'em, you can't work 'em."

73, Jim K9YC
______________________________________________________________
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: NOT the feedline

In reply to this post by Kidder, George

On 6/1/2020 3:31 PM, Walter Underwood wrote:
> Even with a 1:1 SWR, 1000 W is pretty close to the 500 V peak rating for a UHF connector.

The vast majority of HF stations with big power amps use UHF connectors
throughout, and are without such problems as long as quality connectors
are properly installed. The only problems I've ever had with connectors
were the result the connectors being junk quality, and it hasn't been
voltage breakdown. Rather I've had them fall apart, and I've had the
center conductor melt.

73, Jim K9YC
______________________________________________________________
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]

123