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KAT 500 and open wire

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Viggo Magnus Nilsen Nilsen

KAT 500 and open wire

Hello Elecrafters,

Do some of you using KAT500 with open wire,ladder line feed to ur wire
antennas with balun (outside the tuner) ? working ok ?

73' LA9NEA Viggo M.
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Ken G Kopp

Re: KAT 500 and open wire

Yes Viggo I use an open wire CF Zepp via a 4:1 balun with my KAT500. It
works great. (:-))

73

K0PP

On Sun, Jan 6, 2019, 10:01 Viggo Magnus Nilsen Nilsen <[hidden email]
wrote:

> Hello Elecrafters,
>
> Do some of you using KAT500 with open wire,ladder line feed to ur wire
> antennas with balun (outside the tuner) ? working ok ?
>
> 73' LA9NEA Viggo M.
> ______________________________________________________________
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Bob McGraw - K4TAX

Re: KAT 500 and open wire

In reply to this post by Viggo Magnus Nilsen Nilsen

Yes I use a balanced feed line being the "window" type line.   It feeds
a 250 ft wire in the center at 50 feet. I have about 75 ft of feed line
from the center of the antenna then, through the attic eve vent,
supported on some wooden hangers I made and attached to the roof
rafters.   Then it drops through the ceiling to the balun which sits on
the shelf above the KPA500 and the KAT500.   The balun is a Balun
Designs 1:1 ATU current balun rated at 5 kW being model 1171t.    I use
a common mode choke, being model 8232 purchased from The Wireman. It
runs from the balun to one of the tuner 3 outputs.   Works great from
160M through 10M.

Of note, I am on the 2nd floor of a wood frame house more in the
center. No windows or walls to the outside. I do not use any type of
"station ground" to the outside. I do have lightning protection devices
where the feed lines and rotor lines enter the house.   As the antenna
and feed line is quite well balanced, there is no RF radiation in the
shack an thus no RF issues with computers, phones, TV's, surround sound
systems, and such.   Each piece of station equipment is bonded to the
station power supply ground terminal using a dedicated ground jumper.
The 3rd pin AC ground is maintained and the amp runs from a dedicated
240 VAC circuit.

Works great!

73

Bob, K4TAX

On 1/6/2019 10:59 AM, Viggo Magnus Nilsen Nilsen wrote:

K9MA

Re: KAT 500 and open wire

Using a balun with balanced line is risky. Window line or open line can
be used with reasonable losses up to at least a 10:1 SWR, but that means
the impedance at the balun output could be anywhere from 30 to 3000 Ohms
(for 300 Ohm line). The current balun should work if the impedance at
the balun output is low, not much over 50 Ohms. This is hard to measure,
but modeling should give a close enough value. On the other hand, the
impedance could be thousands of Ohms, and that kind of balun will be
ineffective. Transformer-type baluns have limitations at both high and
low impedances.

While a transformer type balun could overheat and/or generate harmonics,
I suppose the worst thing a current balun could do is to upset the
balance. I've you're not seeing a lot of "RF in the shack", you're
probably good.

The only really reliable way to feed unmatched balanced line is with a
truly balanced tuner, a seriously endangered species. I'm still using
the one I built almost 50 years ago.

73,
Scott K9MA

On 1/6/2019 13:42, Bob McGraw K4TAX wrote:

> Yes I use a balanced feed line being the "window" type line.   It
> feeds a 250 ft wire in the center at 50 feet. I have about 75 ft of
> feed line from the center of the antenna then, through the attic eve
> vent, supported on some wooden hangers I made and attached to the roof
> rafters.   Then it drops through the ceiling to the balun which sits
> on the shelf above the KPA500 and the KAT500.   The balun is a Balun
> Designs 1:1 ATU current balun rated at 5 kW being model 1171t.    I
> use a common mode choke, being model 8232 purchased from The Wireman.
> It runs from the balun to one of the tuner 3 outputs.   Works great
> from 160M through 10M.
>
> Of note, I am on the 2nd floor of a wood frame house more in the
> center. No windows or walls to the outside. I do not use any type
> of "station ground" to the outside. I do have lightning protection
> devices where the feed lines and rotor lines enter the house.   As the
> antenna and feed line is quite well balanced, there is no RF radiation
> in the shack an thus no RF issues with computers, phones, TV's,
> surround sound systems, and such.   Each piece of station equipment is
> bonded to the station power supply ground terminal using a dedicated
> ground jumper.   The 3rd pin AC ground is maintained and the amp runs
> from a dedicated 240 VAC circuit.
>
> Works great!
>
> 73
>
> Bob, K4TAX
>
>
> On 1/6/2019 10:59 AM, Viggo Magnus Nilsen Nilsen wrote:
>> Hello Elecrafters,
>>
>> Do some of you using KAT500 with open wire,ladder line feed to ur wire
>> antennas with balun (outside the tuner) ? working ok ?
>>
>> 73' LA9NEA Viggo M.
>> ______________________________________________________________
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>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> Message delivered to [hidden email]
>>
>
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--
Scott K9MA

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Don Wilhelm

Re: KAT 500 and open wire

All,

I think a bit of extended study on transmission lines and their
impedance transformation characteristics is in order - refer to any ARRL
antenna book, even those from the 1950 an 1960 era, not much new has
been added, other than baluns. The feedpoint impedance to the
transmission line can vary from quite low to quite high dependent on the
frequency, the length of line, and the load at the far end. It does NOT
depend on the characteristic impedance of the transmission line. The
ARRL TLW program can do a lot of computation for you.

You may be able to adjust the length of the transmission line so there
is a moderate shack end feedpoint impedance on all bands of interest and
be able to use a good current balun which has either a 1:1 or 4:1
transformation ratio. You have to measure the transmission line at the
point where you intend to install the balun to be sure which to use.

Yes, just hanging any balun on any length of parallel feedline connected
to any length of antenna and expecting it to work without problems is
just not going to happen in all but exceptional cases.
How many cases where you see "this antenna works great" do you see any
mention of how long the parallel feedline may be. Most hams simply
ignore that, but it is likely the most important part of how the antenna
works and what type of balun of you need to use.

Your experience may be very different with the "same" multiband antenna
than your local ham or that in the article you read unless the feedline
length and type is know. I do not see many antenna articles where the
feedline length is mentioned if it is parallel feedline.

With resonant antennas, the feedline length does not matter as long as
the feedpoint impedance of the radiator is the same as the
characteristic impedance of the feedline. In those cases, the feedline
length does not matter, but in all other cases, it matters a lot.

73,
Don W3FPR

On 1/6/2019 3:17 PM, K9MA wrote:

> Using a balun with balanced line is risky. Window line or open line can
> be used with reasonable losses up to at least a 10:1 SWR, but that means
> the impedance at the balun output could be anywhere from 30 to 3000 Ohms
> (for 300 Ohm line). The current balun should work if the impedance at
> the balun output is low, not much over 50 Ohms. This is hard to measure,
> but modeling should give a close enough value. On the other hand, the
> impedance could be thousands of Ohms, and that kind of balun will be
> ineffective. Transformer-type baluns have limitations at both high and
> low impedances.
>
> While a transformer type balun could overheat and/or generate harmonics,
> I suppose the worst thing a current balun could do is to upset the
> balance. I've you're not seeing a lot of "RF in the shack", you're
> probably good.
>
> The only really reliable way to feed unmatched balanced line is with a
> truly balanced tuner, a seriously endangered species. I'm still using
> the one I built almost 50 years ago.
>
> 73,
> Scott K9MA
>

Bob McGraw - K4TAX

Re: KAT 500 and open wire

Correct on all points.

That is the reason I gave my feedline type, and length and antenna
length alone with specific balun type and common mode choke type.   Any
old ragged combination of chunks of wire and feed line is not assured to
work and is largely the reason many hams shy away from balanced feed
systems.     They tried it once, it didn't work well thus they deemed
all balanced feed systems as being "bad".   While the facts are, a
balanced system correctly installed and with correct lengths, it is the
lowest loss feed of any system reasonably available.   Which is one of
the reasons most short wave broadcast stations used balanced feed systems.

73

Bob, K4TAX

On 1/6/2019 3:40 PM, Don Wilhelm wrote:

> All,
>
> I think a bit of extended study on transmission lines and their
> impedance transformation characteristics is in order - refer to any
> ARRL antenna book, even those from the 1950 an 1960 era, not much new
> has been added, other than baluns. The feedpoint impedance to the
> transmission line can vary from quite low to quite high dependent on
> the frequency, the length of line, and the load at the far end. It
> does NOT depend on the characteristic impedance of the transmission
> line. The ARRL TLW program can do a lot of computation for you.
>
> You may be able to adjust the length of the transmission line so there
> is a moderate shack end feedpoint impedance on all bands of interest
> and be able to use a good current balun which has either a 1:1 or 4:1
> transformation ratio. You have to measure the transmission line at
> the point where you intend to install the balun to be sure which to use.
>
> Yes, just hanging any balun on any length of parallel feedline
> connected to any length of antenna and expecting it to work without
> problems is just not going to happen in all but exceptional cases.
> How many cases where you see "this antenna works great" do you see any
> mention of how long the parallel feedline may be. Most hams simply
> ignore that, but it is likely the most important part of how the
> antenna works and what type of balun of you need to use.
>
> Your experience may be very different with the "same" multiband
> antenna than your local ham or that in the article you read unless the
> feedline length and type is know. I do not see many antenna articles
> where the feedline length is mentioned if it is parallel feedline.
>
> With resonant antennas, the feedline length does not matter as long as
> the feedpoint impedance of the radiator is the same as the
> characteristic impedance of the feedline. In those cases, the
> feedline length does not matter, but in all other cases, it matters a
> lot.
>
> 73,
> Don W3FPR
>
> On 1/6/2019 3:17 PM, K9MA wrote:
>> Using a balun with balanced line is risky. Window line or open line
>> can be used with reasonable losses up to at least a 10:1 SWR, but
>> that means the impedance at the balun output could be anywhere from
>> 30 to 3000 Ohms (for 300 Ohm line). The current balun should work if
>> the impedance at the balun output is low, not much over 50 Ohms. This
>> is hard to measure, but modeling should give a close enough value. On
>> the other hand, the impedance could be thousands of Ohms, and that
>> kind of balun will be ineffective. Transformer-type baluns have
>> limitations at both high and low impedances.
>>
>> While a transformer type balun could overheat and/or generate
>> harmonics, I suppose the worst thing a current balun could do is to
>> upset the balance. I've you're not seeing a lot of "RF in the shack",
>> you're probably good.
>>
>> The only really reliable way to feed unmatched balanced line is with
>> a truly balanced tuner, a seriously endangered species. I'm still
>> using the one I built almost 50 years ago.
>>
>> 73,
>> Scott K9MA
>>
> ______________________________________________________________
> 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]

W2xj

Re: KAT 500 and open wire

And those broadcast stations generally work within a 2:1 VSWR range.

Sent from my iPad

> On Jan 6, 2019, at 4:51 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>
> Correct on all points.
>
> That is the reason I gave my feedline type, and length and antenna length alone with specific balun type and common mode choke type. Any old ragged combination of chunks of wire and feed line is not assured to work and is largely the reason many hams shy away from balanced feed systems. They tried it once, it didn't work well thus they deemed all balanced feed systems as being "bad". While the facts are, a balanced system correctly installed and with correct lengths, it is the lowest loss feed of any system reasonably available. Which is one of the reasons most short wave broadcast stations used balanced feed systems.
>
> 73
>
> Bob, K4TAX
>
>
>> On 1/6/2019 3:40 PM, Don Wilhelm wrote:
>> All,
>>
>> I think a bit of extended study on transmission lines and their impedance transformation characteristics is in order - refer to any ARRL antenna book, even those from the 1950 an 1960 era, not much new has been added, other than baluns. The feedpoint impedance to the transmission line can vary from quite low to quite high dependent on the frequency, the length of line, and the load at the far end. It does NOT depend on the characteristic impedance of the transmission line. The ARRL TLW program can do a lot of computation for you.
>>
>> You may be able to adjust the length of the transmission line so there is a moderate shack end feedpoint impedance on all bands of interest and be able to use a good current balun which has either a 1:1 or 4:1 transformation ratio. You have to measure the transmission line at the point where you intend to install the balun to be sure which to use.
>>
>> Yes, just hanging any balun on any length of parallel feedline connected to any length of antenna and expecting it to work without problems is just not going to happen in all but exceptional cases.
>> How many cases where you see "this antenna works great" do you see any mention of how long the parallel feedline may be. Most hams simply ignore that, but it is likely the most important part of how the antenna works and what type of balun of you need to use.
>>
>> Your experience may be very different with the "same" multiband antenna than your local ham or that in the artic

K9MA

Re: KAT 500 and open wire

In reply to this post by Don Wilhelm

Well said, Don!

73,
Scott K9MA

On 1/6/2019 15:40, Don Wilhelm wrote:

K9MA

Re: KAT 500 and open wire

In reply to this post by W2xj

The really attractive thing about open line, and even window line, is
that its loss is so low you can use it at a very high SWR, and take care
of the matching at the station end. This is especially useful for
multi-band antennas. The famous G5RV, for example, will work just
exactly the same fed with window line and a tuner as it will with the
usual matching section.

73,
Scott K9MA

On 1/6/2019 16:09, W2xj wrote:

> And those broadcast stations generally work within a 2:1 VSWR range.
>
> Sent from my iPad
>
>> On Jan 6, 2019, at 4:51 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>>
>> Correct on all points.
>>
>> That is the reason I gave my feedline type, and length and antenna length alone with specific balun type and common mode choke type. Any old ragged combination of chunks of wire and feed line is not assured to work and is largely the reason many hams shy away from balanced feed systems. They tried it once, it didn't work well thus they deemed all balanced feed systems as being "bad". While the facts are, a balanced system correctly installed and with correct lengths, it is the lowest loss feed of any system reasonably available. Which is one of the reasons most short wave broadcast stations used balanced feed systems.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>>> On 1/6/2019 3:40 PM, Don Wilhelm wrote:
>>> All,
>>>
>>> I think a bit of extended study on transmission lines and their impedance transformation characteristics is in order - refer to any ARRL antenna book, even those from the 1950 an 1960 era, not much new has been added, other than baluns. The feedpoint impedance to the transmission line can vary from quite low to quite high dependent on the frequency, the length of line, and the load at the far end. It does NOT depend on the characteristic impedance of the transmission line. The ARRL TLW program can do a lot of computation for you.
>>>
>>> You may be able to adjust the length of the transmission line so there is a moderate shack end feedpoint impedance on all bands of interest and be able to use a good current balun which has either a 1:1 or 4:1 transformation ratio. You have to measure the transmission line at the point where you intend to install the balun to be sure which to use.
>>>
>>> Yes, just hanging any balun on any length of parallel feedline connected to any length of antenna and expecting it to work without problems is just not going to happen in all but exceptional cases.
>>> How many cases where you see "this antenna works great" do you see any mention of how long the parallel feedline may be. Most hams simply ignore that, but it is likely the most important part of how the antenna works and what type of balun of you need to use.
>>>
>>> Your experience may be very different with the "same" multiband antenna than your local ham or that in the artic
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

W2xj

Re: KAT 500 and open wire

In the case of SWBC the matching happens at the TX.

Sent from my iPad

> On Jan 6, 2019, at 5:15 PM, K9MA <[hidden email]> wrote:
>
> The really attractive thing about open line, and even window line, is that its loss is so low you can use it at a very high SWR, and take care of the matching at the station end. This is especially useful for multi-band antennas. The famous G5RV, for example, will work just exactly the same fed with window line and a tuner as it will with the usual matching section.
>
> 73,
> Scott K9MA
>
>> On 1/6/2019 16:09, W2xj wrote:
>> And those broadcast stations generally work within a 2:1 VSWR range.
>>
>> Sent from my iPad
>>
>>> On Jan 6, 2019, at 4:51 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>>>
>>> Correct on all points.
>>>
>>> That is the reason I gave my feedline type, and length and antenna length alone with specific balun type and common mode choke type. Any old ragged combination of chunks of wire and feed line is not assured to work and is largely the reason many hams shy away from balanced feed systems. They tried it once, it didn't work well thus they deemed all balanced feed systems as being "bad". While the facts are, a balanced system correctly installed and with correct lengths, it is the lowest loss feed of any system reasonably available. Which is one of the reasons most short wave broadcast stations used balanced feed systems.
>>>
>>> 73
>>>
>>> Bob, K4TAX
>>>
>>>
>>>> On 1/6/2019 3:40 PM, Don Wilhelm wrote:
>>>> All,
>>>>
>>>> I think a bit of extended study on transmission lines and their impedance transformation characteristics is in order - refer to any ARRL antenna book, even those from the 1950 an 1960 era, not much new has been added, other than baluns. The feedpoint impedance to the transmission line can vary from quite low to quite high dependent on the frequency, the length of line, and the load at the far end. It does NOT depend on the characteristic impedance of the transmission line. The ARRL TLW program can do a lot of computation for you.
>>>>
>>>> You may be able to adjust the length of the transmission line so there is a moderate shack end feedpoint impedance on all bands of interest and be able to use a good current balun which has either a 1:1 or 4:1 transformation ratio. You have to measure the transmission line at the point where you intend to install the balun to be sure which to use.
>>>>
>>>> Yes, just hanging any balun on any length of parallel feedline connected to any length of antenna and expecting it to work without problems is just not going to happen in all but exceptional cases.
>>>> How many cases where you see "this antenna works great" do you see any mention of how long the parallel feedline may be. Most hams simply ignore that, but it is likely the most important part of how the antenna works and what type of balun of you need to use.
>>>>
>>>> Your experience may be very different with the "same" multiband antenna than your local ham or that in the artic
>> ______________________________________________________________
>> 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]
>
>
> --
> Scott K9MA
>
> [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Message delivered to [hidden email]
>

Don Wilhelm

Re: KAT 500 and open wire

In reply to this post by K9MA

Scott,

As I indicated, that is NOT true of just any length of window line.
Some will work while others will not.

With the G5RV, the only thing we know for sure is that on 20 meters, the
impedance at the end of 34 feet of 300 ohm feedline is approximately 75
ohms.
The impedance at that point will not be the same for other bands, and
that is why a tuner is required.

Once you get RF onto the radiator, it will be radiated. One real
question is just how much loss do you encounter in the feedline. The
other real question is, how much trouble do you have matching the shack
end impedance to the 50 ohm output requirement of the transceiver.

In days of old when we used plug-in coils in the transmitter and tuned
the output tank to resonance, we could tap off those PA tank coils to
match most any impedance. That capability moved into the antenna tuner
with the advent of 50 ohm only transceivers - the first antenna tuners
used balanced plug-in coils which could handle both balanced and
unbalanced feedline, as well as low to high impedance depending on where
you placed the tap(s) on the coil.
The problem with those tuners is that they were not conducive to rapid
band changes - you had to plug in coils for a different band.

The Johnson Matchbox was a great asset to band changing and the proper
taps on the coils, but its matching range was much more limited than
those old-fashioned plug-in coils which provided a very wide range of
matching impedance.

73,
Don W3FPR

On 1/6/2019 5:15 PM, K9MA wrote:
> The really attractive thing about open line, and even window line, is
> that its loss is so low you can use it at a very high SWR, and take care
> of the matching at the station end. This is especially useful for
> multi-band antennas. The famous G5RV, for example, will work just
> exactly the same fed with window line and a tuner as it will with the
> usual matching section.
>
______________________________________________________________
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Brian Hunt

Re: KAT 500 and open wire

In reply to this post by W2xj

I learned a lot about my low band antenna system by building a full model of it using EZNEC and SimSmith. It enabled me to learn where the losses were band by band and resulted in a few changes. On 80m SimSmith said the loss in the 450 ohm was high because of the specific type I was using. It needed replacing anyway so I home brewed a length of ladder line and picked up over a dB. YMMV.

73, Brian, K0DTJ

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K9MA

Re: KAT 500 and open wire

In reply to this post by Don Wilhelm

Don,

I guess I should have pointed out that I was assuming one of those
wide-range, balanced tuners of days of yore. I have one of those
plug-in coil tuners I built long ago, and it will match almost anything,
so feedline length is seldom an issue. Alas, the commercial tuners
available today have much smaller ranges, so one does have to ensure
that the impedance is in range, both of the tuner and the balun.

73,
Scott K9MA

On 1/6/2019 16:44, Don Wilhelm wrote:

> Scott,
>
> As I indicated, that is NOT true of just any length of window line.
> Some will work while others will not.
>
> With the G5RV, the only thing we know for sure is that on 20 meters,
> the impedance at the end of 34 feet of 300 ohm feedline is
> approximately 75 ohms.
> The impedance at that point will not be the same for other bands, and
> that is why a tuner is required.
>
> Once you get RF onto the radiator, it will be radiated. One real
> question is just how much loss do you encounter in the feedline. The
> other real question is, how much trouble do you have matching the
> shack end impedance to the 50 ohm output requirement of the transceiver.
>
> In days of old when we used plug-in coils in the transmitter and tuned
> the output tank to resonance, we could tap off those PA tank coils to
> match most any impedance. That capability moved into the antenna
> tuner with the advent of 50 ohm only transceivers - the first antenna
> tuners used balanced plug-in coils which could handle both balanced
> and unbalanced feedline, as well as low to high impedance depending on
> where you placed the tap(s) on the coil.
> The problem with those tuners is that they were not conducive to rapid
> band changes - you had to plug in coils for a different band.
>
> The Johnson Matchbox was a great asset to band changing and the proper
> taps on the coils, but its matching range was much more limited than
> those old-fashioned plug-in coils which provided a very wide range of
> matching impedance.
>
> 73,
> Don W3FPR
>
> On 1/6/2019 5:15 PM, K9MA wrote:
>> The really attractive thing about open line, and even window line, is
>> that its loss is so low you can use it at a very high SWR, and take
>> care of the matching at the station end. This is especially useful
>> for multi-band antennas. The famous G5RV, for example, will work just
>> exactly the same fed with window line and a tuner as it will with the
>> usual matching section.
>>

David Woolley (E.L)

Re: KAT 500 and open wire

In reply to this post by Don Wilhelm

The feedpoint impedance DOES depend on the characteristic impedance!

Taking pure resistive cases (real characteristic impedances aren't), and
lossless lines, a 75 ohm load at the end of a 75 ohm transmission line
will have a feed point impedance that is a constant 75 ohms, whereas a
75 ohm load on 300 ohm feeder will have a feed point impedance that
swings from 75 to 1200 ohms.

--
David Woolley
Owner K2 06123

On 06/01/2019 21:40, Don Wilhelm wrote:
> The feedpoint impedance to the transmission line can vary from quite low
> to quite high dependent on the frequency, the length of line, and the
> load at the far end. It does NOT depend on the characteristic impedance
> of the transmission line.

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Jim Brown-10

Re: KAT 500 and open wire

I think we're confused here about the meaning the words "feedpoint
impedance." It is the impedance of THE ANTENNA at the point where the
feedline is attached, and it is determined entirely by the antenna,
INCLUDING the common mode circuit of the feedline. That common mode
circuit consists of the feedline, any chokes and matching elements, and
whatever it is connected to in the shack. The ONLY contribution of the
feedline to this is as a common mode element, and in the common mode
circuit it looks like a wire connected between the feedpoint and the shack.

We add one or more common mode chokes to minimize the effect if the
common mode circuit, which is radiation and reception, and to do that, a
very good choke must be AT THE FEEDPOINT. I don't know of a way to
EFFECTIVELY choke a feedline that is not matched to the antenna. Yes,
you can put something there, but if it did anything useful it would fry
(unless yo only ran QRP to the antena), and a choke that wouldn't fry
with TX power won't do anything useful!

A few other points: 1) the SWR on a feedline is established BY THE
ANTENNA, not the transmitter or antenna tuner; 2) feeding an antenna
with two-wire line does NOT make it balanced -- most practical antennas
that we think of as balanced are often un-balanced by their surroundings
-- ground slope, variations in the soil under them, trees, wiring in
buildings, unequal height ; 3) off-center-fed antennas are inherently
unbalanced.

73, Jim K9YC

On 1/6/2019 3:51 PM, David Woolley wrote:
> he feedpoint impedance DOES depend on the characteristic impedance!

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Bob McGraw - K4TAX

Re: KAT 500 and open wire

I agree with Jim on this point. I have means to measure current in
each side of the balanced feed line. And I have means to measure the
voltage on each leg and observe the phase difference in each leg. A
dual trace scope with 2 current probes is the basic configuration. If
the currents are equal in each leg, and the voltage is equal in each
leg, and the phase is 180 degrees between the two legs, the system is
well balanced.

As I stated earlier, random installation of an antenna and feed line
will likely lead to random and usually unfavorable results. Otherwise,
careful installation and positioning of the antenna legs and feed line
run produces wonderful results.

73

Bob, K4TAX

On 1/6/2019 8:12 PM, Jim Brown wrote:
> A few other points: 1) the SWR on a feedline is established BY THE
> ANTENNA, not the transmitter or antenna tuner; 2) feeding an antenna
> with two-wire line does NOT make it balanced -- most practical
> antennas that we think of as balanced are often un-balanced by their
> surroundings -- ground slope, variations in the soil under them,
> trees, wiring in buildings, unequal height ; 3) off-center-fed
> antennas are inherently unbalanced.
>
> 73, Jim K9YC

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Bob McGraw - K4TAX

Re: KAT 500 and open wire

In reply to this post by Jim Brown-10

I agree with Jim on this point. I have means to measure current in
each side of the balanced feed line. And I have means to measure the
voltage on each leg and observe the phase difference in each leg. A
dual trace scope with 2 current probes is the basic configuration. If
the currents are equal in each leg, and the voltage is equal in each
leg, and the phase is 180 degrees between the two legs, the system is
well balanced.

As I stated earlier, random installation of an antenna and feed line
will likely lead to random and usually unfavorable results. Otherwise,
careful installation and positioning of the antenna legs and feed line
run produces wonderful results. It is not that difficult to do. It
just takes a bit of planning and careful attention to detail.
Otherwise, just hang some commercial version of a touted antenna in a
tree and be done with it.

73

Bob, K4TAX

On 1/6/2019 8:12 PM, Jim Brown wrote:
> A few other points: 1) the SWR on a feedline is established BY THE
> ANTENNA, not the transmitter or antenna tuner; 2) feeding an antenna
> with two-wire line does NOT make it balanced -- most practical
> antennas that we think of as balanced are often un-balanced by their
> surroundings -- ground slope, variations in the soil under them,
> trees, wiring in buildings, unequal height ; 3) off-center-fed
> antennas are inherently unbalanced.
>
> 73, Jim K9YC

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K9MA

Re: KAT 500 and open wire

In reply to this post by Jim Brown-10

On 1/6/2019 20:12, Jim Brown wrote:
> We add one or more common mode chokes to minimize the effect if the
> common mode circuit, which is radiation and reception, and to do that,
> a very good choke must be AT THE FEEDPOINT. I don't know of a way to
> EFFECTIVELY choke a feedline that is not matched to the antenna. Yes,
> you can put something there, but if it did anything useful it would
> fry (unless yo only ran QRP to the antena), and a choke that wouldn't
> fry with TX power won't do anything useful!

I have to respectfully disagree a little here. A choke specifically
designed for the antenna impedance at the feed point could effectively
eliminate the common mode current. The problem is, we often use balanced
line with antennas which have a large range of impedances over frequency
range at which they are used. (Think G5RV.) It may be impossible to
design a single choke which can work over the whole range. However,
feeding balanced line with a balanced tuner can work pretty well, even
though the feedline may radiate a bit due to common mode current. I've
only attempted this with link-coupled tuners. I'm not sure it works as
well with the double T-network tuners with a choke at the input, like
the MFJ-976, but it may.

For years, I've used a warped, lop-sided, short, 80 meter "dipole" fed
with window line and the balanced tuner. I never bothered to try to
figure out the impedance at either the feedpoint or the tuner, but the
tuner matches it on several bands. I don't use it much on 80, though, as
it's so close to the roof of my house that the RF gets into everything.
I'm sure the feedline radiates some, but that's not where the RFI is
coming from.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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Charlie T, K3ICH

Re: KAT 500 and open wire

I should probably know this, but what is the old dual air coil Heathkit B-1
balun, a current or voltage type?
If I remember correctly, they are 4:1 ratio.
Would this be a better choice for open-wire feed to a dipole intended for
use on several bands?

73, Charlie k3ICH

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of K9MA
Sent: Sunday, January 06, 2019 10:24 PM
To: [hidden email]
Subject: Re: [Elecraft] KAT 500 and open wire

On 1/6/2019 20:12, Jim Brown wrote:
> We add one or more common mode chokes to minimize the effect if the
> common mode circuit, which is radiation and reception, and to do that,
> a very good choke must be AT THE FEEDPOINT. I don't know of a way to
> EFFECTIVELY choke a feedline that is not matched to the antenna. Yes,
> you can put something there, but if it did anything useful it would
> fry (unless yo only ran QRP to the antena), and a choke that wouldn't
> fry with TX power won't do anything useful!

I have to respectfully disagree a little here. A choke specifically designed
for the antenna impedance at the feed point could effectively eliminate the
common mode current. The problem is, we often use balanced line with
antennas which have a large range of impedances over frequency range at
which they are used. (Think G5RV.) It may be impossible to design a single
choke which can work over the whole range. However, feeding balanced line
with a balanced tuner can work pretty well, even though the feedline may
radiate a bit due to common mode current. I've only attempted this with
link-coupled tuners. I'm not sure it works as well with the double T-network
tuners with a choke at the input, like the MFJ-976, but it may.

For years, I've used a warped, lop-sided, short, 80 meter "dipole" fed with
window line and the balanced tuner. I never bothered to try to figure out
the impedance at either the feedpoint or the tuner, but the tuner matches it
on several bands. I don't use it much on 80, though, as it's so close to the
roof of my house that the RF gets into everything.
I'm sure the feedline radiates some, but that's not where the RFI is coming
from.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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K9MA

Re: KAT 500 and open wire

The B-1 is indeed 4:1. It would be useful only for matched balanced
lines. Unless you have a folded dipole, you probably don't have a match
balanced line.

73,
Scott K9MA

On 1/6/2019 22:17, Charlie T wrote:

> I should probably know this, but what is the old dual air coil Heathkit B-1
> balun, a current or voltage type?
> If I remember correctly, they are 4:1 ratio.
> Would this be a better choice for open-wire feed to a dipole intended for
> use on several bands?
>
> 73, Charlie k3ICH
>
>
>
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On
> Behalf Of K9MA
> Sent: Sunday, January 06, 2019 10:24 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KAT 500 and open wire
>
> On 1/6/2019 20:12, Jim Brown wrote:
>> We add one or more common mode chokes to minimize the effect if the
>> common mode circuit, which is radiation and reception, and to do that,
>> a very good choke must be AT THE FEEDPOINT. I don't know of a way to
>> EFFECTIVELY choke a feedline that is not matched to the antenna. Yes,
>> you can put something there, but if it did anything useful it would
>> fry (unless yo only ran QRP to the antena), and a choke that wouldn't
>> fry with TX power won't do anything useful!
> I have to respectfully disagree a little here. A choke specifically designed
> for the antenna impedance at the feed point could effectively eliminate the
> common mode current. The problem is, we often use balanced line with
> antennas which have a large range of impedances over frequency range at
> which they are used. (Think G5RV.) It may be impossible to design a single
> choke which can work over the whole range. However, feeding balanced line
> with a balanced tuner can work pretty well, even though the feedline may
> radiate a bit due to common mode current. I've only attempted this with
> link-coupled tuners. I'm not sure it works as well with the double T-network
> tuners with a choke at the input, like the MFJ-976, but it may.
>
> For years, I've used a warped, lop-sided, short, 80 meter "dipole" fed with
> window line and the balanced tuner. I never bothered to try to figure out
> the impedance at either the feedpoint or the tuner, but the tuner matches it
> on several bands. I don't use it much on 80, though, as it's so close to the
> roof of my house that the RF gets into everything.
> I'm sure the feedline radiates some, but that's not where the RFI is coming
> from.
>
> 73,
>
> Scott K9MA
>
> --
> Scott K9MA
>
> [hidden email]
>
> ______________________________________________________________
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> delivered to [hidden email]
>
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