Re: [Elecraft] KX2 Antenna Curiosity

[rich hurd WC3T]

Simple is good

On Fri, Oct 11, 2019 at 07:07 Gwen Patton  wrote:

> I have a KX3 instead of a KX2, but I frequently go out in the field to play
> radio at local parks and other scenic spots. I have a number of antennas,
> but one of my favorites is one I built recently, a link dipole for 40, 30,
> and 20. It's tuned for the CW portions of the bands, so it doesn't need
> much tuning, but if I want to work phone I hit the internal tuner just to
> tweak it a little bit. I suspend it on top of a 20-foot telescopic
> fiberglass pole from SOTABeams, secured in a drive-on mount and held down
> by one of the tires of my E-150 conversion van. I run it in inverted-V
> configuration, using stakes or photographers' sandbags at the far ends if
> the location doesn't like stakes.
>
> I didn't bother with baluns or anything. I just wired the coax to the
> midpoint and trimmed it up that way using an analyzer. I get good results
> with it on CW or phone, easily going from the Philadelphia suburbs to the
> Michigan Upper Penninsula on 40m phone with 10 watts. If I find that I'm
> getting stray RF, I have a big isolator choke I can run the line through
> that clobbers it nicely.
>
> 73,
> Gwen, NG3P
>
> On Fri, Oct 11, 2019 at 6:55 AM CUTTER DAVID via Elecraft <
> elecraft@mailman.qth.net> wrote:
>
> > I'd like to suggest that one very good reason for using centre-fed and
> > external matching unit is because the harmonic pickup from nearby
> stations
> > is much reduced compared to multi-band antennas.  This is best
> implemented
> > when the antenna is as near perfectly balanced as possible to avoid
> > feedline pickup.  A *proper* choke to cancel out-of-balance currents
> should
> > be helpful in this regard.
> >
> > For single station field days, I've used the Spiderbeam 807
> off-centre-fed
> > inverted V dipole on a f/g pole which is a fast way to get on air without
> > an external matching unit to fiddle with. Common mode current is
> virtually
> > zero. It's a great solution for beginners reducing the fiddle factor, ie
> > plug and play KISS.  Less to carry out into the field as well.
> >
> > David G3UNA/G6CP
> > __
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>
>
> --
>
> -+-+-+-+-
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> http://quarktime.net
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-- 
72,
Rich Hurd / WC3T / DMR: 3142737
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*
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Re: [Elecraft] KX2 Antenna Curiosity

[Gwen Patton]

I have a KX3 instead of a KX2, but I frequently go out in the field to play
radio at local parks and other scenic spots. I have a number of antennas,
but one of my favorites is one I built recently, a link dipole for 40, 30,
and 20. It's tuned for the CW portions of the bands, so it doesn't need
much tuning, but if I want to work phone I hit the internal tuner just to
tweak it a little bit. I suspend it on top of a 20-foot telescopic
fiberglass pole from SOTABeams, secured in a drive-on mount and held down
by one of the tires of my E-150 conversion van. I run it in inverted-V
configuration, using stakes or photographers' sandbags at the far ends if
the location doesn't like stakes.

I didn't bother with baluns or anything. I just wired the coax to the
midpoint and trimmed it up that way using an analyzer. I get good results
with it on CW or phone, easily going from the Philadelphia suburbs to the
Michigan Upper Penninsula on 40m phone with 10 watts. If I find that I'm
getting stray RF, I have a big isolator choke I can run the line through
that clobbers it nicely.

73,
Gwen, NG3P

On Fri, Oct 11, 2019 at 6:55 AM CUTTER DAVID via Elecraft <
elecraft@mailman.qth.net> wrote:

> I'd like to suggest that one very good reason for using centre-fed and
> external matching unit is because the harmonic pickup from nearby stations
> is much reduced compared to multi-band antennas.  This is best implemented
> when the antenna is as near perfectly balanced as possible to avoid
> feedline pickup.  A *proper* choke to cancel out-of-balance currents should
> be helpful in this regard.
>
> For single station field days, I've used the Spiderbeam 807 off-centre-fed
> inverted V dipole on a f/g pole which is a fast way to get on air without
> an external matching unit to fiddle with. Common mode current is virtually
> zero. It's a great solution for beginners reducing the fiddle factor, ie
> plug and play KISS.  Less to carry out into the field as well.
>
> David G3UNA/G6CP
> __
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> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to ard...@gmail.com
>


-- 

-+-+-+-+-
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http://quarktime.net
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Re: [Elecraft] KX2 Antenna Curiosity

[CUTTER DAVID via Elecraft]

I'd like to suggest that one very good reason for using centre-fed and external 
matching unit is because the harmonic pickup from nearby stations is much 
reduced compared to multi-band antennas.  This is best implemented when the 
antenna is as near perfectly balanced as possible to avoid feedline pickup.  A 
*proper* choke to cancel out-of-balance currents should be helpful in this 
regard. 

For single station field days, I've used the Spiderbeam 807 off-centre-fed 
inverted V dipole on a f/g pole which is a fast way to get on air without an 
external matching unit to fiddle with. Common mode current is virtually zero. 
It's a great solution for beginners reducing the fiddle factor, ie plug and 
play KISS.  Less to carry out into the field as well. 

David G3UNA/G6CP
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Re: [Elecraft] KX2 Antenna Curiosity

[Bob McGraw K4TAX]

The only issue I've encountered with single band antennas, to staff a 
Field Day site to operate 2 or 3 stations per band, and 5 bands, there 
needs to be some 10 to 15 antennas erected.    Where as a single 135 ft 
wire with a balanced feed system, a good 1:1 balun, and a good tuner 
{not one of those internal radio 3:1 tuners} will allow each station to 
operate 5 bands with one antenna.   Thus 3 stations = 3 antennas.   That 
greatly simplifies operation and installation.


After all Field Day was conceived to allow hams to operate under less 
than ideal conditions and to commence operation as expediently as 
possible.   I don't think installing 10 to 15 antennas for 2 or 3 
stations falls under the definition of expediently.


I totally agree with Joe, W4TV where he says "The one "multiband" 
antenna one can use in a multi-transmitter
configuration is the flat-top with open wire feeders and a *Link 
coupled* tuner.  The link coupled tuner is a bandpass filter
that significantly reduces harmonic/broadband noise just like the "Q" of 
a single band antenna."


The optimum end result of any multi transmitter site is to have clean 
transmitters.   We've been begging for better receivers, now it is time 
to beg for cleaner transmitters.


73

Bob, K4TAX



On 10/10/2019 1:59 PM, Tim N9PUZ wrote:

If you are talking about a single band dipole then any half wave dipole cut
to the standard formula and fed with good quality coax should work well. If
you want a "multi band" dipole then I would recommend cutting it for the
lowest frequency you plan to operate and feeding it with balanced line.
Even the best coax can have a lot of loss under high SWR conditions
(between your tuner and the antenna feedpoint) whereas even at 1 10:1 SWR
balanced line does not have much loss. The radiation pattern of a multi
band configuration can vary a lot from band to band.

The end fed wire you describe is not specific to the KX2. You typically
want the longest wire possible that is NOT a half wavelength or even
multiple on any band you want to operate. The main reason for this is when
a wire is a half wave or an even multiple the impedance at the end of the
wire can be very high and it is more difficult for most tuners to obtain a
match there. By it NOT being a half wave, the impedance is lower and a wide
range tuner like the one in your KX2 can match it more easily and present
the proper impedance to the radio.

Here is an article that suggests good lengths for a "random wire" antenna.
The lengths aren't really very random, they are specifically chosen to be
easier to match. At 58.5 feet you arrived at one of the good lengths.



Tim N9PUZ

On Thu, Oct 10, 2019 at 11:03 AM Joseph Shuman via Elecraft <
elecraft@mailman.qth.net> wrote:


I have had my KX2 with the ATU for about 10 months and operate on 40m QRP
SSB from various locations.  Experimenting with different antennas I have
experienced best results with a 58.5’ wire tossed about 25’ up a tree with
a 16.5’ counterpoise.  I ran the same length wire from my house to the
workshop, grounded the shield side of the cable, and have seen similar
results to the field setup.

Is there some engineering/design factor of the KX2 for this type of
antenna setup?  I am planning to setup a Dipole at home, but as a newbie am
wondering if the “ideal” Ham Dipole can be expected to improve performance.

Keeping Watch-
shu

Joe Shuman
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Re: [Elecraft] KX2 Antenna Curiosity

[Grant Youngman]

Absolutely.  The other advantage of a horizontal dipole (or inverted V) is that 
it will be far quieter than the wire.

An end fed non-resonant wire installed as a sort-of sloper “works” but is far 
from optimum.  Especially since you’re using a minimal counterpoise system.  
One counterpoise wire (elevated) is far from being optimum.  But sure, you can 
make contacts on one.

That said, we all deal with what we have available.  As someone else said, a 
resonant vertical with an adequate radial system will work very well, too, if 
you have the space.  A vertical will be good for DX,  So will a dipole at a 1/2 
wave up.  The dipole at lower heights (or an inverted V if you can’t hang it 
high from both ends) will be far better for local to medium range contacts than 
the vertical.  It depends on your objectives.

I’ve been experimenting with this same kind of non-resonant end-fed wire 
antenna on 20M because in my living situation it is supposedly good for multi 
band operation.  It works poorly everywhere.  My 20M Buddipole vertical (with 4 
elevated radials) works better than that wire.  I recently got a 20M horizontal 
antenna bent around in my restricted space, and it is so much quieter, and 
works well, too.

I’d also suggest a thorough reading of the ARRL Antenna Book if you haven’t 
done so :-)

Grant NQ5T
KX3 (8342)/KXPA100


> On Oct 10, 2019, at 2:59 PM, Tim N9PUZ  wrote:
> 
> If you are talking about a single band dipole then any half wave dipole cut
> to the standard formula and fed with good quality coax should work well. 
> 
> 
>>  I am planning to setup a Dipole at home, but as a newbie am
>> wondering if the “ideal” Ham Dipole can be expected to improve performance.
>> 

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Re: [Elecraft] KX2 Antenna Curiosity

[Don Wilhelm]

Shu,

If you add the 58.5 foot wire to the 16.5' counterpoise, you have a 75 
foot antenna.  That is close to a half wavelength on 40 meters.  You are 
feeding it off-center which will allow it to be used on several bands 
(even though one of the antenna wires is on the ground).
As I recall, Bruce Prior (one of the KX2 Field Testers) recommended 
those lengths for 40 meters thru 10 meters.
If you feed those 2 wires directly from the KX2 tuner using a BNC to 
binding post adapter, you do not have to worry about feedline loss - 
there is no feedline!
If you do use a feedline, I suggest ladder line rather than coax because 
it will not have as much loss in the feedline due to an impedance mismatch.


The KX2/KX3/K3 ATUs have a very wide matching range and this antenna 
will work fine with any of their tuners.


73,
Don W3FPR

On 10/10/2019 12:01 PM, Joseph Shuman via Elecraft wrote:

I have had my KX2 with the ATU for about 10 months and operate on 40m QRP SSB 
from various locations.  Experimenting with different antennas I have 
experienced best results with a 58.5’ wire tossed about 25’ up a tree with a 
16.5’ counterpoise.  I ran the same length wire from my house to the workshop, 
grounded the shield side of the cable, and have seen similar results to the 
field setup.


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Re: [Elecraft] KX2 Antenna Curiosity

[Tim N9PUZ]

If you are talking about a single band dipole then any half wave dipole cut
to the standard formula and fed with good quality coax should work well. If
you want a "multi band" dipole then I would recommend cutting it for the
lowest frequency you plan to operate and feeding it with balanced line.
Even the best coax can have a lot of loss under high SWR conditions
(between your tuner and the antenna feedpoint) whereas even at 1 10:1 SWR
balanced line does not have much loss. The radiation pattern of a multi
band configuration can vary a lot from band to band.

The end fed wire you describe is not specific to the KX2. You typically
want the longest wire possible that is NOT a half wavelength or even
multiple on any band you want to operate. The main reason for this is when
a wire is a half wave or an even multiple the impedance at the end of the
wire can be very high and it is more difficult for most tuners to obtain a
match there. By it NOT being a half wave, the impedance is lower and a wide
range tuner like the one in your KX2 can match it more easily and present
the proper impedance to the radio.

Here is an article that suggests good lengths for a "random wire" antenna.
The lengths aren't really very random, they are specifically chosen to be
easier to match. At 58.5 feet you arrived at one of the good lengths.



Tim N9PUZ

On Thu, Oct 10, 2019 at 11:03 AM Joseph Shuman via Elecraft <
elecraft@mailman.qth.net> wrote:

> I have had my KX2 with the ATU for about 10 months and operate on 40m QRP
> SSB from various locations.  Experimenting with different antennas I have
> experienced best results with a 58.5’ wire tossed about 25’ up a tree with
> a 16.5’ counterpoise.  I ran the same length wire from my house to the
> workshop, grounded the shield side of the cable, and have seen similar
> results to the field setup.
>
> Is there some engineering/design factor of the KX2 for this type of
> antenna setup?  I am planning to setup a Dipole at home, but as a newbie am
> wondering if the “ideal” Ham Dipole can be expected to improve performance.
>
> Keeping Watch-
> shu
>
> Joe Shuman
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Re: [Elecraft] KX2 Antenna Curiosity

[David Gilbert]

Your field antenna is essentially a very low off-center fed sloped 
dipole slightly longer than a half wavelength.  I'm not surprised you 
can tune it with the KX2, but it certainly isn't any kind of ideal 
antenna configuration that Elecraft would design for.  They just made a 
very well performing tuner for the KX2 that will work with almost 
anything.  I have a KX2 ... it's amazing what it can tune.


You didn't say how long your feedline is, but with a feed that far off 
center the shield of your coax is probably doing some of the radiating 
anyway.


Yes, a center fed normal dipole with the middle (high current portion) 
higher off the ground (say 50 feet for 40m) and a common mode choke at 
the feedpoint would almost assuredly perform better. If you can't get it 
that high, a vertical (even a 30 foot wire oriented mostly straight up) 
fed against a decent radial system might be a better choice if you don't 
have a lot of surrounding buildings/trees/telephone poles.


For the record, I also have on rare occasions used low sloped wires fed 
near one end against some sort of ground or counterpoise when camping or 
for a hurried Field Day setup.  They are easy to set up and sort of 
work, but they always performed very poorly compared to even the most 
basic dipole if I could get the dipole off the ground approaching a half 
wavelength in height.  Over the years I have operated roughly 20 Field 
Day contests (almost always 5 watts CW for the extra QRP points) and one 
year I used only a low sloped wire similar to what you described.  It 
was memorable for being the worst Field Day result I have ever had, and 
that's in spite of the fact that I've placed top 3 nationwide in my 
category on more than one occasion using only wire antennas strung from 
tall trees.


73,
Dave   AB7E



On 10/10/2019 9:01 AM, Joseph Shuman via Elecraft wrote:

I have had my KX2 with the ATU for about 10 months and operate on 40m QRP SSB 
from various locations.  Experimenting with different antennas I have 
experienced best results with a 58.5’ wire tossed about 25’ up a tree with a 
16.5’ counterpoise.  I ran the same length wire from my house to the workshop, 
grounded the shield side of the cable, and have seen similar results to the 
field setup.

Is there some engineering/design factor of the KX2 for this type of antenna 
setup?  I am planning to setup a Dipole at home, but as a newbie am wondering 
if the “ideal” Ham Dipole can be expected to improve performance.

Keeping Watch-
shu

Joe Shuman


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[Elecraft] KX2 Antenna Curiosity

[Joseph Shuman via Elecraft]

I have had my KX2 with the ATU for about 10 months and operate on 40m QRP SSB 
from various locations.  Experimenting with different antennas I have 
experienced best results with a 58.5’ wire tossed about 25’ up a tree with a 
16.5’ counterpoise.  I ran the same length wire from my house to the workshop, 
grounded the shield side of the cable, and have seen similar results to the 
field setup.  

Is there some engineering/design factor of the KX2 for this type of antenna 
setup?  I am planning to setup a Dipole at home, but as a newbie am wondering 
if the “ideal” Ham Dipole can be expected to improve performance.

Keeping Watch-
shu

Joe Shuman
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