Elecraft

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

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Bob McGraw - K4TAX

Re: NOT the feedline

I agree with Jim, K9YC on these points.

** OCFD antennas are noted to have lots of common mode current issues.
These are a chore to tame.

** Most commercial baluns or common mode chokes are poor designs, of
inadequate material, designs copied from other poor designs but packed
in a pretty box of different color, size, and shape with a high price.

One of the best applications for a 4:1 balun is with a single band
folded dipole made of equal wire diameter or size. Depending on height
above ground the feed point Z is between 200 and 300 ohms. The use of a
4:1 give an impedance of 50 to 75 ohms. Any other usage of a 4:1
balun is more of a compromise to a disaster.

73

Bob, K4TAX

On 6/1/2020 9:41 PM, Jim Brown wrote:

> On 6/1/2020 6:45 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.
>
> 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
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Jim Brown-10

Re: NOT the feedline

In reply to this post by Peter W2IRT

On 6/1/2020 5:47 PM, Peter Dougherty wrote:
> Ten-Tec Tuner,

This might be it, Peter. ! I've used (and loved) the Ten Tec 229 and 238
tuners, but some of their fixed capacitors are under-rated for power.
This is fairly well known among Ten Tec users, so I read about it
somewhere and replaced those in my tuners with caps having higher power
ratings.

There's another design flaw -- their antenna selection switch fails to
to provide a return for RF current, using the chassis instead. This adds
inductance in series with the signal path, which increasingly degrades
SWR and crosstalk with increasing frequency. Palstar makes the same
mistake in tuners I saw at Dayton 8-10 years ago. When I pointed it out
to a guy in their booth who claimed to be its designer, he told me I was
crazy!

73, Jim K9YC
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Adrian-3

Re: NOT the feedline

In reply to this post by Bob McGraw - K4TAX

My experience is that the Balun-Designs 4:1 current balun works
brilliantly on a well designed ocf antenna with decent height and
proportions to

provide good band sync at the same impedance point, where the different
band sine waves intersect, at the approx 1/3 total length feedpoint.
shown in below from ;

https://archive.org/details/UnderstandingAndBuildingTheOCFDipole

However these days I use delta loops, beams and verticals.

Adrian Fewster

On 2/6/20 1:01 pm, Bob McGraw K4TAX wrote:

> I agree with Jim, K9YC on these points.
>
> ** OCFD antennas are noted to have lots of common mode current
> issues. These are a chore to tame.
>
> ** Most commercial baluns or common mode chokes are poor designs, of
> inadequate material, designs copied from other poor designs but packed
> in a pretty box of different color, size, and shape with a high price.
>
> One of the best applications for a 4:1 balun is with a single band
> folded dipole made of equal wire diameter or size. Depending on height
> above ground the feed point Z is between 200 and 300 ohms. The use of
> a 4:1 give an impedance of 50 to 75 ohms. Any other usage of a 4:1
> balun is more of a compromise to a disaster.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 9:41 PM, Jim Brown wrote:
>> On 6/1/2020 6:45 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.
>>
>> 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]
>
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Adrian-3

Re: NOT the feedline

In reply to this post by Jim Brown-10

My recent experience with Palstar has not been good. An expensive DL1500
dummy load in which the SO239 had not been mounted correct bwith the
locknut still ten turns loose,

requiring dismantle and repair new out of the box by myself. Also a new
expensive AT2K tuner in which the roller inductor shaft had not been
graphite greased nor tensioned.

My SPE amp @ 400w went out on alarm quickly until I disassembled and
repaired myself. I found Palstar support rude and in self denial of the
issues I raised.

In hindsight I should have saved a heap of money and gone with MFJ.

On 2/6/20 1:08 pm, Jim Brown wrote:

> On 6/1/2020 5:47 PM, Peter Dougherty wrote:
>> Ten-Tec Tuner,
>
> This might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> 238 tuners, but some of their fixed capacitors are under-rated for
> power. This is fairly well known among Ten Tec users, so I read about
> it somewhere and replaced those in my tuners with caps having higher
> power ratings.
>
> There's another design flaw -- their antenna selection switch fails to
> to provide a return for RF current, using the chassis instead. This
> adds inductance in series with the signal path, which increasingly
> degrades SWR and crosstalk with increasing frequency. Palstar makes
> the same mistake in tuners I saw at Dayton 8-10 years ago. When I
> pointed it out to a guy in their booth who claimed to be its designer,
> he told me I was crazy!
>
> 73, Jim K9YC
>

Bob McGraw - K4TAX

Re: NOT the feedline

In reply to this post by Jim Brown-10

Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
circuit when in the bypass position. This does not allow the tuner,
even in bypass mode, to work well as an antenna switch on 6M.

  The capacitors in question are not rated for the RF current
experienced under certain load Z conditions. They heat, change value,
and the SWR creeps up. Allow them to cool and the SWR is back to the
starting point.    I usually tweaked mine such that the SWR started off
a bit high, came down as I transmitted and if transmitting a bit longer
the SWR increased.   Later I got tired of this and changed the group of
disk ceramic caps to 470 pf Russian doorknob caps. Problem solved.

73

Bob, K4TAX

On 6/1/2020 10:08 PM, Jim Brown wrote:
> his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> 238 tuners, but some of their fixed capacitors are under-rated for
> power. This is fairly well known among Ten Tec users, so I read about
> it somewhere and replaced those in my tuners with caps having higher
> power ratings.

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Vic Rosenthal

Re: NOT the feedline

In reply to this post by Peter W2IRT

Pardon me if this has already been covered, but do you have the same problem if you connect the antenna to ANT-2 on the KPA? I know you don’t want to do this permanently, but just as a test.

Victor 4X6GP

> On 2 Jun 2020, at 3:47, 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
>>>>
>>>
>>> ______________________________________________________________
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>>
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Peter W2IRT

Re: NOT the feedline

In reply to this post by Adrian-3

I have an HF-Auto that is just unsuitable for contest/DX duty, even with the kludge workaround software--which often doesn't work right. I gave up on it and hope to sell it to a ragchewer who will undoubtedly make better use of it than I ever could.

And I agree about the Palstar support being...unpleasant. I saved up for 3 years to buy that and I feel sick about it. I would like to find a good high-quality tuner that is reliable and able to comfortably handle 1500W and (preferably) tune automatically via CAT control.

- pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Adrian
Sent: Monday, June 1, 2020 11:32 PM
To: [hidden email]
Subject: Re: [Elecraft] NOT the feedline

My recent experience with Palstar has not been good. An expensive DL1500 dummy load in which the SO239 had not been mounted correct bwith the locknut still ten turns loose,

requiring dismantle and repair new out of the box by myself. Also a new expensive AT2K tuner in which the roller inductor shaft had not been graphite greased nor tensioned.

My SPE amp @ 400w went out on alarm quickly until I disassembled and repaired myself. I found Palstar support rude and in self denial of the issues I raised.

In hindsight I should have saved a heap of money and gone with MFJ.

On 2/6/20 1:08 pm, Jim Brown wrote:

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

Peter W2IRT

Re: NOT the feedline

In reply to this post by Vic Rosenthal

It's a BIT better on ANT-2, but still faults out on occasion, and I'm not getting a true SWR reading. It is slightly more stable, though, to answer your question.

- pjd

-----Original Message-----
From: Vic Rosenthal <[hidden email]>
Sent: Tuesday, June 2, 2020 1:01 AM
To: Peter Dougherty <[hidden email]>
Cc: Jack Brindle <[hidden email]>; [hidden email]
Subject: Re: [Elecraft] NOT the feedline

Pardon me if this has already been covered, but do you have the same problem if you connect the antenna to ANT-2 on the KPA? I know you don’t want to do this permanently, but just as a test.

Victor 4X6GP

> On 2 Jun 2020, at 3:47, 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]
>>
>> ______________________________________________________________
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>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email
>> list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
>>
>> ______________________________________________________________
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>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email
>> list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
>
>
> ______________________________________________________________
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>
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> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]

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

donovanf

Re: NOT the feedline

In reply to this post by Jim Brown-10

The Amphenol 83-1SP connector that many of us use is rated at 1000
volts RMS, That well exceeds the voltage that most amateur 1500
watt amplifiers can safely produce without much more severe internal
damage to the amplifier.

www.amphenolrf.com/media/downloads/305/C83-1sp.pdf

73
Frank
W3LPL

----- Original Message -----

From: "Jim Brown" <[hidden email]>
To: [hidden email]
Sent: Tuesday, June 2, 2020 2:59:17 AM
Subject: Re: [Elecraft] NOT the feedline

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
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Mark Goldberg

Re: NOT the feedline

In reply to this post by Bob McGraw - K4TAX

I want to mention that my LDG AT-600Pro has a minimum capacitance that is
too high for a good match to my antenna on 6 meters. Certainly seems like
removing the Ten Tec tuner would be a good thing to try. Can you open the
Ten Tec tuner and use an IR thermometer to monitor the components? I don't
know anything about it's construction. You could see them heating up.

Just running medium power of maybe 500W would slow things down and let you
see the SWR increasing before the amp trips. That would confirm that
something is heating up vs arcing.

73,

Mark
W7MLG

On Mon, Jun 1, 2020 at 9:01 PM Bob McGraw K4TAX <[hidden email]> wrote:

> Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
> circuit when in the bypass position. This does not allow the tuner,
> even in bypass mode, to work well as an antenna switch on 6M.
>
> The capacitors in question are not rated for the RF current
> experienced under certain load Z conditions. They heat, change value,
> and the SWR creeps up. Allow them to cool and the SWR is back to the
> starting point. I usually tweaked mine such that the SWR started off
> a bit high, came down as I transmitted and if transmitting a bit longer
> the SWR increased. Later I got tired of this and changed the group of
> disk ceramic caps to 470 pf Russian doorknob caps. Problem solved.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 10:08 PM, Jim Brown wrote:
> > his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> > 238 tuners, but some of their fixed capacitors are under-rated for
> > power. This is fairly well known among Ten Tec users, so I read about
> > it somewhere and replaced those in my tuners with caps having higher
> > power ratings.
>
> ______________________________________________________________
> 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 Kidder, George

Walter,
Yes, the UHF connector may be rated at 500V, but in practice they handle >4KV. The voltage limit is set by the air gap between the center pin and the shield. I have not had a PL-259 arc over.
73,
N2TK, Tony

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Walter Underwood
Sent: Monday, June 1, 2020 6:32 PM
To: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] NOT the feedline

Even with a 1:1 SWR, 1000 W is pretty close to the 500 V peak rating for a UHF connector. Type N connectors are rated at 1500 V peak.

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Jun 1, 2020, at 3:17 PM, George Kidder <[hidden email]> wrote:
>
> 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]
> ______________________________________________________________
> 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]

john@kk9a.com

Re: NOT the feedline

In reply to this post by Alan - G4GNX

The RMS voltage for 1000 watts into a perfect load is <250 volts. I
suspect that Tony's 4,000 voltage limit is closer to what a quality
PL-259 can actually handle. If the PL-259 is arcing, there is
something very wrong with either the connector, the weatherproofing or
the antenna.

John KK9A

tony.kaz N2Tk wrote:

Walter,
Yes, the UHF connector may be rated at 500V, but in practice they
handle >4KV. The voltage limit is set by the air gap between the
center pin and the shield. I have not had a PL-259 arc over.
73,
N2TK, Tony

-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at
mailman.qth.net> On Behalf Of Walter Underwood
Sent: Monday, June 1, 2020 6:32 PM
To: Elecraft Reflector <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] NOT the feedline

Even with a 1:1 SWR, 1000 W is pretty close to the 500 V peak rating
for a UHF connector. Type N connectors are rated at 1500 V peak.

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

______________________________________________________________
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Post: mailto:[hidden email]

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Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: NOT the feedline

In reply to this post by Mark Goldberg

As a rule, if one needs a tuner to get a good match on 6M, I'd say they
need to look carefully at their antenna system. My 6M yagi shows less
than 1.5:1 over the lower 2 MHz of the band, 50.0 - 52.0 MHz. The
lowest SWR occurs at 50.2 with a Z value of 42 ohms and an X value of
0.0. Of course higher gain antennas typically have a bit less
bandwidth, but still, the lower 1 MHz should be totally usable without a
tuner.

Besides, tuners only make the transmitter happy and the added feed line
loss due to SWR still remains.

73

Bob, K4TAX

On 6/2/2020 1:09 AM, Mark Goldberg wrote:

> I want to mention that my LDG AT-600Pro has a minimum capacitance that
> is too high for a good match to my antenna on 6 meters. Certainly
> seems like removing the Ten Tec tuner would be a good thing to try.
> Can you open the Ten Tec tuner and use an IR thermometer to monitor
> the components? I don't know anything about it's construction. You
> could see them heating up.
>
> Just running medium power of maybe 500W would slow things down and let
> you see the SWR increasing before the amp trips. That would confirm
> that something is heating up vs arcing.
>
> 73,
>
> Mark
> W7MLG
>
> On Mon, Jun 1, 2020 at 9:01 PM Bob McGraw K4TAX <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
> circuit when in the bypass position. This does not allow the tuner,
> even in bypass mode, to work well as an antenna switch on 6M.
>
>   The capacitors in question are not rated for the RF current
> experienced under certain load Z conditions. They heat, change
> value,
> and the SWR creeps up. Allow them to cool and the SWR is back to the
> starting point.    I usually tweaked mine such that the SWR
> started off
> a bit high, came down as I transmitted and if transmitting a bit
> longer
> the SWR increased.   Later I got tired of this and changed the
> group of
> disk ceramic caps to 470 pf Russian doorknob caps. Problem solved.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 10:08 PM, Jim Brown wrote:
> > his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> > 238 tuners, but some of their fixed capacitors are under-rated for
> > power. This is fairly well known among Ten Tec users, so I read
> about
> > it somewhere and replaced those in my tuners with caps having
> higher
> > power ratings.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
> <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]
> <mailto:[hidden email]>
>

Peter W2IRT

Re: NOT the feedline

In reply to this post by Mark Goldberg

Just to clarify, I was **NOT** using the tuner to tune the 6m antenna
system. I was using it as a coax switch, so I could keep the KPA-1500
powered down (silencing the very noisy PSU fan) and still be able to receive
6m as well as other bands.

I need the room to be quiet since my XYL is working-from-home a few feet
away from me in the same room, and the KPA's power supply fan is bothersome
to both her and me.

Ideally, the KPA-1500 should be able to default to either ANT-1 or ANT-2 in
power-down mode but that is not the case. So I need a quiet alternative. I'm
not a fan of tuners of any kind.

In any event, the TT-238 is out of line now and the SWR problem is
MARGINALLY better on the KPA-1500. It's still showing a higher SWR than the
antenna analyzer measured but it hasn't folded back yet.

- pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Mark Goldberg
Sent: Tuesday, June 2, 2020 2:10 AM
To: Bob McGraw K4TAX <[hidden email]>
Cc: Elecraft Mailing List <[hidden email]>
Subject: Re: [Elecraft] NOT the feedline

I want to mention that my LDG AT-600Pro has a minimum capacitance that is
too high for a good match to my antenna on 6 meters. Certainly seems like
removing the Ten Tec tuner would be a good thing to try. Can you open the
Ten Tec tuner and use an IR thermometer to monitor the components? I don't
know anything about it's construction. You could see them heating up.

Just running medium power of maybe 500W would slow things down and let you
see the SWR increasing before the amp trips. That would confirm that
something is heating up vs arcing.

73,

Mark
W7MLG

On Mon, Jun 1, 2020 at 9:01 PM Bob McGraw K4TAX <[hidden email]> wrote:

> Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
> circuit when in the bypass position. This does not allow the tuner,
> even in bypass mode, to work well as an antenna switch on 6M.
>
> The capacitors in question are not rated for the RF current
> experienced under certain load Z conditions. They heat, change value,
> and the SWR creeps up. Allow them to cool and the SWR is back to the
> starting point. I usually tweaked mine such that the SWR started off
> a bit high, came down as I transmitted and if transmitting a bit longer
> the SWR increased. Later I got tired of this and changed the group of
> disk ceramic caps to 470 pf Russian doorknob caps. Problem solved.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 10:08 PM, Jim Brown wrote:
> > his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> > 238 tuners, but some of their fixed capacitors are under-rated for
> > power. This is fairly well known among Ten Tec users, so I read
> > about it somewhere and replaced those in my tuners with caps having
> > higher power ratings.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email
> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]

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Message delivered to [hidden email]

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

Bob McGraw - K4TAX

Re: NOT the feedline

In reply to this post by john@kk9a.com

It is correct that there is no such thing as a breakdown voltage, as
stated earlier. This becomes obvious since the units are given as V/m,
which is represents Volts per meter, or Electric Field strength.

Also, unless one is measuring the field in between two plane parallel
metallic plates, the Electric Field will, in general, not be uniform,
I.e., the field strength (the amount of "pull" on an electron), will
vary with position. This shape does matter, and sharply pointed emitters
can cause breakdown at values considerably less than the maximum
measured in a uniform field.

The Volts/meter relationship is also pressure-dependent, and this
relationship goes nonlinear at low pressures (not enough charge
carriers) following Paschen's law
<https://en.wikipedia.org/wiki/Paschen%27s_law>. It also varies with
humidity and other contaminants, which usually increase arcing.

73

Bob, K4TAX

On 6/2/2020 8:54 AM, [hidden email] wrote:

>
> The RMS voltage for 1000 watts into a perfect load is <250 volts. I
> suspect that Tony's 4,000 voltage limit is closer to what a quality
> PL-259 can actually handle. If the PL-259 is arcing, there is
> something very wrong with either the connector, the weatherproofing or
> the antenna.
>
> John KK9A
>
>
>
>

Mark Goldberg

Re: NOT the feedline

In reply to this post by Bob McGraw - K4TAX

I failed to mention, my antenna system is a 300 ft long horizontal loop fed
by ladder line with a homebrew two core switchable 1:1 or 4:1 Guanella
current mode Balun. The Balun has a measured return loss of about 32 dB at
50 MHz with a 200 ohm resistive load. That was surprisingly good, but
confirmed with a calibrated VNA. Yes, I spent some time with Jerry Sevick's
book.

The antenna is not deluxe for 50 MHz, but it is all I have. It's just so
happens that only small values are required in the tuner to match it, and
the LDG tuner parasitic capacitance it too high even when in bypass mode. I
expect it is difficult to build a physically large high power tuner and
keep the parasitics down, so the Ten Tec may have similar issues. As I
said, I know nothing about it. From Peter's most recent email, this may be
the case.

73,

Mark
W7MLG

On Tue, Jun 2, 2020 at 8:26 AM Bob McGraw K4TAX <[hidden email]> wrote:

> As a rule, if one needs a tuner to get a good match on 6M, I'd say they
> need to look carefully at their antenna system. My 6M yagi shows less than
> 1.5:1 over the lower 2 MHz of the band, 50.0 - 52.0 MHz. The lowest SWR
> occurs at 50.2 with a Z value of 42 ohms and an X value of 0.0. Of course
> higher gain antennas typically have a bit less bandwidth, but still, the
> lower 1 MHz should be totally usable without a tuner.
>
> Besides, tuners only make the transmitter happy and the added feed line
> loss due to SWR still remains.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/2/2020 1:09 AM, Mark Goldberg wrote:
>
> I want to mention that my LDG AT-600Pro has a minimum capacitance that is
> too high for a good match to my antenna on 6 meters. Certainly seems like
> removing the Ten Tec tuner would be a good thing to try. Can you open the
> Ten Tec tuner and use an IR thermometer to monitor the components? I don't
> know anything about it's construction. You could see them heating up.
>
> Just running medium power of maybe 500W would slow things down and let you
> see the SWR increasing before the amp trips. That would confirm that
> something is heating up vs arcing.
>
> 73,
>
> Mark
> W7MLG
>
>

Bob McGraw - K4TAX

Re: NOT the feedline

The Tentec 238 tuner does have some values of L and C components in the
circuit when in the Bypass mode. These are L1 which is 0.3uH and C7 &
C8 which are 250 pf in series. The tuner is designed for use between
1.8 and 30 MHz. Thus I would not advise using it as an antenna switch
on 50 MHz and certainly not to resolve a match on 50 MHz.

You may find that adjustment in the ladder line length {just a couple of
ft, more or less, for 6M} will aid in the LDG tuner finding a better
match with existing component values and parasitic capacitance.

73

Bob, K4TAX

On 6/2/2020 10:53 AM, Mark Goldberg wrote:

> I failed to mention, my antenna system is a 300 ft long horizontal
> loop fed by ladder line with a homebrew two core switchable 1:1 or 4:1
> Guanella current mode Balun. The Balun has a measured return loss of
> about 32 dB at 50 MHz with a 200 ohm resistive load. That was
> surprisingly good, but confirmed with a calibrated VNA. Yes, I spent
> some time with Jerry Sevick's book.
>
> The antenna is not deluxe for 50 MHz, but it is all I have. It's just
> so happens that only small values are required in the tuner to match
> it, and the LDG tuner parasitic capacitance it too high even when in
> bypass mode. I expect it is difficult to build a physically large high
> power tuner and keep the parasitics down, so the Ten Tec may have
> similar issues. As I said, I know nothing about it. From Peter's most
> recent email, this may be the case.
>
> 73,
>
> Mark
> W7MLG
>
> On Tue, Jun 2, 2020 at 8:26 AM Bob McGraw K4TAX <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> As a rule, if one needs a tuner to get a good match on 6M, I'd say
> they need to look carefully at their antenna system. My 6M yagi
> shows less than 1.5:1 over the lower 2 MHz of the band, 50.0 -
> 52.0 MHz. The lowest SWR occurs at 50.2 with a Z value of 42 ohms
> and an X value of 0.0. Of course higher gain antennas typically
> have a bit less bandwidth, but still, the lower 1 MHz should be
> totally usable without a tuner.
>
> Besides, tuners only make the transmitter happy and the added feed
> line loss due to SWR still remains.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/2/2020 1:09 AM, Mark Goldberg wrote:
>> I want to mention that my LDG AT-600Pro has a minimum capacitance
>> that is too high for a good match to my antenna on 6 meters.
>> Certainly seems like removing the Ten Tec tuner would be a good
>> thing to try. Can you open the Ten Tec tuner and use an IR
>> thermometer to monitor the components? I don't know anything
>> about it's construction. You could see them heating up.
>>
>> Just running medium power of maybe 500W would slow things down
>> and let you see the SWR increasing before the amp trips. That
>> would confirm that something is heating up vs arcing.
>>
>> 73,
>>
>> Mark
>> W7MLG
>>

Ed Pflueger

Re: NOT the feedline

In reply to this post by Bob McGraw - K4TAX

I have a HY-Gain VB-66DX and 1.4 is the normal case basically across the whole band. I must be messing up somewhere, even the KPA1500 likes it. I have never run it over 1200 Watts on 6 meters and never requires over 30 watts drive to obtain 1200 out. I have three feet of 213U from amp to Palstar HF-AUTO (Bypass Mode), 70ft. of 9913 from the Palstar to a DX-Engineering 8 position Antenna switch, to my lightening protection and the final trip of 40ft of 213U to the antenna. The antenna is actually 10ft. above my HY-GAIN TH11 which also does not require a tuner. The Palstar is my antenna switch essentially but I do need it on my HY-GAIN HY-TOWER only on 160 and 80 meters when needed.

That's the end of my good luck story. LOL

Ed..AB4IQ

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Bob McGraw K4TAX
Sent: Tuesday, June 2, 2020 10:27 AM
To: Mark Goldberg <[hidden email]>
Cc: Elecraft Mailing List <[hidden email]>
Subject: Re: [Elecraft] NOT the feedline

As a rule, if one needs a tuner to get a good match on 6M, I'd say they need to look carefully at their antenna system. My 6M yagi shows less than 1.5:1 over the lower 2 MHz of the band, 50.0 - 52.0 MHz. The lowest SWR occurs at 50.2 with a Z value of 42 ohms and an X value of 0.0. Of course higher gain antennas typically have a bit less bandwidth, but still, the lower 1 MHz should be totally usable without a tuner.

Besides, tuners only make the transmitter happy and the added feed line loss due to SWR still remains.

73

Bob, K4TAX

On 6/2/2020 1:09 AM, Mark Goldberg wrote:

> I want to mention that my LDG AT-600Pro has a minimum capacitance that
> is too high for a good match to my antenna on 6 meters. Certainly
> seems like removing the Ten Tec tuner would be a good thing to try.
> Can you open the Ten Tec tuner and use an IR thermometer to monitor
> the components? I don't know anything about it's construction. You
> could see them heating up.
>
> Just running medium power of maybe 500W would slow things down and let
> you see the SWR increasing before the amp trips. That would confirm
> that something is heating up vs arcing.
>
> 73,
>
> Mark
> W7MLG
>
> On Mon, Jun 1, 2020 at 9:01 PM Bob McGraw K4TAX <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
> circuit when in the bypass position. This does not allow the tuner,
> even in bypass mode, to work well as an antenna switch on 6M.
>
> The capacitors in question are not rated for the RF current
> experienced under certain load Z conditions. They heat, change
> value,
> and the SWR creeps up. Allow them to cool and the SWR is back to the
> starting point. I usually tweaked mine such that the SWR
> started off
> a bit high, came down as I transmitted and if transmitting a bit
> longer
> the SWR increased. Later I got tired of this and changed the
> group of
> disk ceramic caps to 470 pf Russian doorknob caps. Problem solved.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 10:08 PM, Jim Brown wrote:
> > his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> > 238 tuners, but some of their fixed capacitors are under-rated for
> > power. This is fairly well known among Ten Tec users, so I read
> about
> > it somewhere and replaced those in my tuners with caps having
> higher
> > power ratings.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
> <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]
> <mailto:[hidden email]>
>

123