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KX3 with BL2 Question

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stan levandowski

KX3 with BL2 Question

When operating a KX3 with the internal ATU into a window line fed
doublet through a BL2 balun, what is the preferred connection method:

1. Placing the BL2 right at the KX3 output eliminating any coax. This
puts the window line right next to the metal KX3, everything else on the
operating desk and the operator.

2. Placing the BL2 five feet away and higher which puts the window line
further away and connecting it to the KX3 through a short coax jumper.

3. Placing the balun (weathered-proofed) right at the doublet's center
and using coax for the whole run to the KX3.

Thanks and 73,
Stan WB2LQF

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Don Wilhelm

Re: KX3 with BL2 Question

Stan,

Either of those options will work - however ---
I would suggest minimizing the coax. The balun will not transform to a
50 ohm load, so the coax can run at a high SWR which will give more loss
than the window line.

Whether that minimum is zero or 5 feet will not make a significant
difference, so use whatever is convenient for your station.

73,
Don W3FPR

On 10/4/2017 9:26 AM, stan levandowski wrote:
> When operating a KX3 with the internal ATU into a window line fed
> doublet through a BL2 balun, what is the preferred connection method:
>
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rich hurd WC3T

Re: KX3 with BL2 Question

Would not a bnc-to-banana plug adapter hooked to a doublet made from 100'
of zip cord be equally useful? Is there even a reason to have a balun
in-circuit? I've read the characteristic impedance of the zip cord (or
speaker wire, etc.) is about 75 ohms. If you "unzipped" 67 feet or so and
put on a tie wrap (to avoid further unzipping), you'd have a quite
serviceable 40 meter dipole with an SWR of 1.5:1 or so.

---
72,
Rich Hurd / WC3T / DMR: 3142737
PA Army MARS, Northampton County RACES, EPA-ARRL Public Information Officer
for Scouting
Latitude: 40.761621 Longitude: -75.288988 (40°45.68' N 75°17.33' W) Grid:
*FN20is*

On Wed, Oct 4, 2017 at 10:00 AM, Don Wilhelm <[hidden email]> wrote:

> Stan,
>
> Either of those options will work - however ---
> I would suggest minimizing the coax. The balun will not transform to a 50
> ohm load, so the coax can run at a high SWR which will give more loss than
> the window line.
>
> Whether that minimum is zero or 5 feet will not make a significant
> difference, so use whatever is convenient for your station.
>
> 73,
> Don W3FPR
>
> On 10/4/2017 9:26 AM, stan levandowski wrote:
>
>> When operating a KX3 with the internal ATU into a window line fed doublet
>> through a BL2 balun, what is the preferred connection method:
>>
>> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Don Wilhelm

Re: KX3 with BL2 Question

Rich,

It is a common misconception that the characteristic impedance of the
feedline is what you will have to match. That is only true for resonant
antennas. The feedpoint impedance of a dipole in free space is 72 ohms,
but when mounted at practical heights above ground, the feedpoint
impedance will drop. For most HF antennas, 50 ohms is a better choice.

The other point is - yes, a balun is a good thing. For parallel
feedline, the balun should be at the junction of the coax and the
parallel feedline to keep the antenna and feedline currents opposite and
equal (the required condition for balanced), and to keep common mode
current to a minimum.

For non-resonant antennas, the feedpoint impedance of the line at the
transmitter can vary from very low to very high. It all depends on the
length of the feedline, the length of the radiator and the frequency.
In many cases, feeding an antenna with 450 ohm feedline, a 1:1 balun
will work better than a 4:1 balun.
You must match the feedpoint impedance, and that is not the
characteristic impedance of the line.

BTW, zip cord is quite lossy at RF, and should only be used in
situations where nothing else is available.
Your example will work, but it is a one band antenna. The main reason
for using parallel feedline is to be able to use the antenna on multiple
bands.

73,
Don W3FPR

On 10/4/2017 10:35 AM, rich hurd WC3T wrote:
> Would not a bnc-to-banana plug adapter hooked to a doublet made from
> 100' of zip cord be equally useful? Is there even a reason to have a
> balun in-circuit? I've read the characteristic impedance of the zip
> cord (or speaker wire, etc.) is about 75 ohms. If you "unzipped" 67
> feet or so and put on a tie wrap (to avoid further unzipping), you'd
> have a quite serviceable 40 meter dipole with an SWR of 1.5:1 or so.
>

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rich hurd WC3T

Re: KX3 with BL2 Question

Thanks for the feedback.

---
72,
Rich Hurd / WC3T / DMR: 3142737
PA Army MARS, Northampton County RACES, EPA-ARRL Public Information Officer
for Scouting
Latitude: 40.761621 Longitude: -75.288988 (40°45.68' N 75°17.33' W) Grid:
*FN20is*

On Wed, Oct 4, 2017 at 11:50 AM, Don Wilhelm <[hidden email]> wrote:

> Rich,
>
> It is a common misconception that the characteristic impedance of the
> feedline is what you will have to match. That is only true for resonant
> antennas. The feedpoint impedance of a dipole in free space is 72 ohms,
> but when mounted at practical heights above ground, the feedpoint impedance
> will drop. For most HF antennas, 50 ohms is a better choice.
>
> The other point is - yes, a balun is a good thing. For parallel feedline,
> the balun should be at the junction of the coax and the parallel feedline
> to keep the antenna and feedline currents opposite and equal (the required
> condition for balanced), and to keep common mode current to a minimum.
>
> For non-resonant antennas, the feedpoint impedance of the line at the
> transmitter can vary from very low to very high. It all depends on the
> length of the feedline, the length of the radiator and the frequency.
> In many cases, feeding an antenna with 450 ohm feedline, a 1:1 balun will
> work better than a 4:1 balun.
> You must match the feedpoint impedance, and that is not the characteristic
> impedance of the line.
>
> BTW, zip cord is quite lossy at RF, and should only be used in situations
> where nothing else is available.
> Your example will work, but it is a one band antenna. The main reason for
> using parallel feedline is to be able to use the antenna on multiple bands.
>
> 73,
> Don W3FPR
>
>
> On 10/4/2017 10:35 AM, rich hurd WC3T wrote:
>
>> Would not a bnc-to-banana plug adapter hooked to a doublet made from 100'
>> of zip cord be equally useful? Is there even a reason to have a balun
>> in-circuit? I've read the characteristic impedance of the zip cord (or
>> speaker wire, etc.) is about 75 ohms. If you "unzipped" 67 feet or so and
>> put on a tie wrap (to avoid further unzipping), you'd have a quite
>> serviceable 40 meter dipole with an SWR of 1.5:1 or so.
>>
>>
>

stan levandowski

Re: KX3 with BL2 Question

In reply to this post by stan levandowski

Thank you to everyone for the rapid responses. Now I know my options.
As a long time feedpoint autocoupler user, this is a new approach for me
and it's nice to get advice before cutting wire and cable up.
73, Stan WB2LQF

On Wed, Oct 04, 2017 at 09:26 AM, stan levandowski wrote:

> When operating a KX3 with the internal ATU into a window line fed
> doublet through a BL2 balun, what is the preferred connection method:
>
> 1. Placing the BL2 right at the KX3 output eliminating any coax.
> This puts the window line right next to the metal KX3, everything else
> on the operating desk and the operator.
>
>
> 2. Placing the BL2 five feet away and higher which puts the window
> line further away and connecting it to the KX3 through a short coax
> jumper.
>
>
> 3. Placing the balun (weathered-proofed) right at the doublet's
> center and using coax for the whole run to the KX3.
>
>
> Thanks and 73,
> Stan WB2LQF
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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>

Nr4c

Re: KX3 with BL2 Question

In reply to this post by rich hurd WC3T

You can also tie an underwriters knot at the split point.

Actually 67 feet twice makes a 135 foot dipole for 80 meters, not 40.

Sent from my iPhone
...nr4c. bill

> On Oct 4, 2017, at 10:35 AM, rich hurd WC3T <[hidden email]> wrote:
>
> Would not a bnc-to-banana plug adapter hooked to a doublet made from 100'
> of zip cord be equally useful? Is there even a reason to have a balun
> in-circuit? I've read the characteristic impedance of the zip cord (or
> speaker wire, etc.) is about 75 ohms. If you "unzipped" 67 feet or so and
> put on a tie wrap (to avoid further unzipping), you'd have a quite
> serviceable 40 meter dipole with an SWR of 1.5:1 or so.
>
> ---
> 72,
> Rich Hurd / WC3T / DMR: 3142737
> PA Army MARS, Northampton County RACES, EPA-ARRL Public Information Officer
> for Scouting
> Latitude: 40.761621 Longitude: -75.288988 (40°45.68' N 75°17.33' W) Grid:
> *FN20is*
>
>
>> On Wed, Oct 4, 2017 at 10:00 AM, Don Wilhelm <[hidden email]> wrote:
>>
>> Stan,
>>
>> Either of those options will work - however ---
>> I would suggest minimizing the coax. The balun will not transform to a 50
>> ohm load, so the coax can run at a high SWR which will give more loss than
>> the window line.
>>
>> Whether that minimum is zero or 5 feet will not make a significant
>> difference, so use whatever is convenient for your station.
>>
>> 73,
>> Don W3FPR
>>
>>> On 10/4/2017 9:26 AM, stan levandowski wrote:
>>>
>>> When operating a KX3 with the internal ATU into a window line fed doublet
>>> through a BL2 balun, what is the preferred connection method:
>>>
>>> ______________________________________________________________
>> 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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>
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> Message delivered to [hidden email]

rich hurd WC3T

Re: KX3 with BL2 Question

Thanks for catching the math error. Shows the dangers of multitasking.
:)

---
72,
Rich Hurd / WC3T / DMR: 3142737
PA Army MARS, Northampton County RACES, EPA-ARRL Public Information Officer
for Scouting
Latitude: 40.761621 Longitude: -75.288988 (40°45.68' N 75°17.33' W) Grid:
*FN20is*

On Wed, Oct 4, 2017 at 1:33 PM, Nr4c <[hidden email]> wrote:

> You can also tie an underwriters knot at the split point.
>
> Actually 67 feet twice makes a 135 foot dipole for 80 meters, not 40.
>
>
> Sent from my iPhone
> ...nr4c. bill
>
>
> > On Oct 4, 2017, at 10:35 AM, rich hurd WC3T <[hidden email]> wrote:
> >
> > Would not a bnc-to-banana plug adapter hooked to a doublet made from 100'
> > of zip cord be equally useful? Is there even a reason to have a balun
> > in-circuit? I've read the characteristic impedance of the zip cord (or
> > speaker wire, etc.) is about 75 ohms. If you "unzipped" 67 feet or so
> and
> > put on a tie wrap (to avoid further unzipping), you'd have a quite
> > serviceable 40 meter dipole with an SWR of 1.5:1 or so.
> >
> > ---
> > 72,
> > Rich Hurd / WC3T / DMR: 3142737
> > PA Army MARS, Northampton County RACES, EPA-ARRL Public Information
> Officer
> > for Scouting
> > Latitude: 40.761621 Longitude: -75.288988 (40°45.68' N 75°17.33' W)
> Grid:
> > *FN20is*
> >
> >
> >> On Wed, Oct 4, 2017 at 10:00 AM, Don Wilhelm <[hidden email]>
> wrote:
> >>
> >> Stan,
> >>
> >> Either of those options will work - however ---
> >> I would suggest minimizing the coax. The balun will not transform to a
> 50
> >> ohm load, so the coax can run at a high SWR which will give more loss
> than
> >> the window line.
> >>
> >> Whether that minimum is zero or 5 feet will not make a significant
> >> difference, so use whatever is convenient for your station.
> >>
> >> 73,
> >> Don W3FPR
> >>
> >>> On 10/4/2017 9:26 AM, stan levandowski wrote:
> >>>
> >>> When operating a KX3 with the internal ATU into a window line fed
> doublet
> >>> through a BL2 balun, what is the preferred connection method:
> >>>
> >>> ______________________________________________________________
> >> 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]
>
>

Ignacy

Re: KX3 with BL2 Question

As mentioned before, the best option is ladderline attached directly to BL2
on KX3.

I am using KX3 with BL1 set to 4:1 using random wires. I also use a direct
BNC-banana plug connection.
With the direct connection, match is obtained on many some but not all
bands, and often only after second pressing of the ATU button. On some
bands, touching KX3 causes SWR to rise. So impedances may be too complex for
KXAT3 to match, a match may include very high losses in KXAT3, and KX3 is
part of the antenna.

With BL1, the match is always achieved, with antenna or without. No changing
of SWR with touching. So BL1 insulates KX3 from the antenna and 1) reduces
impedances to levels more easily matched by KXAT3 and 2) introduces own
losses. I prefer BL1 because its better to heat the balun than the tuner.

Ignacy, NO9E

--
Sent from: http://elecraft.365791.n2.nabble.com/
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John Oppenheimer

Re: KX3 with BL2 Question

Hi Stan:

Post ten.

There are two ways to approach this, just put something up, or measure
and optimize. When using the KX3 ATU, both methods will provide similar
results.

An 88 foot Doublet and feedline is modeled using EZNEC and SimSmith. The
results found here:
http://www.kn5l.net/Doublet88/

The Balun, both 1:1 and 4:1 is modeled with a perfect conventional
transformer block "A." The KX3 ATU is modeled with the L-C network block
"LC1." A five foot RG-58A/U between the Balun and KX3 is added.

For modeling, Wireman 551 is used and tuned for optimal results on 40
and 20. As shown, a 1:1 Balun results with the best match with SWR below
1.5:1 on both 40 and 20 at the KX3. With system loss below 1 dB.

For this antenna, other bands will have a better match with a 4:1 Balun,
with loses below 1.5 dB.

What is shown is that there is only about 0.5 dB difference between the
optimal and just put it up approach on 40 and above. Using a BL2 and
switching between 1:1 and 4:1 depending on the band.

A short antenna will have a very low impedance, causing the additional
feedline loss to increase significantly, Greater than 4.5 dB is for 80.

John KN5L
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David Woolley (E.L)

Re: KX3 with BL2 Question

On 05/10/17 14:19, John Oppenheimer wrote:

> The Balun, both 1:1 and 4:1 is modeled with a perfect conventional
> transformer block "A." The KX3 ATU is modeled with the L-C network block
> "LC1." A five foot RG-58A/U between the Balun and KX3 is added.

A perfect transformer is not a good model for two reasons:

1) The number of turns is too low to have a leakage inductance that is
large enough to ignore, especially at lower frequencies; I think this is
particularly true for the 4:1 configuration;

2) The general wisdom seems to be that you want a lossy core, so that
the common mode current sees more of a real than imaginary impedance.

--
David Woolley
K2 06123
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