RE: Effective Antennas for use with K2 ATU

[Nicolas Pike]

Hi,

My K2 is complete and I will finish the auto ATU tonight. I am sure this is
FAQ please feel free to refer me! So, here goes..

What simple Antennas would you recommend for use with my K2 and the built in
auto ATU for

1. Base station use, a small back garden 30ft by 22ft? My "shack" is on the
first floor in a room facing the garden. At the moment I have no holes in
the wall!! If I have to run wires around the window frame to start with that
is fine. Just keen to get going!!
2. Portable, by the seaside or in a pub garden?

Thanks!

Regards
Nicolas
www.m1hog.com


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[Stuart Rohre]

Nicolas, you will never go wrong with the simple dipole.  With your
restricted space, you might have to bend a dipole to fit, but that should be
considered as opposed to a less effective antenna.

The 44 foot dipole plus the tuner hits a number of good DX bands.  You can
bend it to fit your space.

Running the feeder crosswise thru some foam tubing placed under the window
sash is one way to handle the feedline entry.

If using twin lead (flat balanced line), you can simply lay it across the
window sill, and cushion the crossing again with foam protection, or not
close the window completely.  Put a locking "L" bracket above the sash to
prevent the window being raised off the crossing to preserve security.
72,
Stuart
K5KVH


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[Ron D'Eau Claire-2]

I'll second Stewart's recommendation whole-heartedly, Nicholas. I also have
a very small garden and use a doublet fed with open wire line. The doublet
is a total of 45 feet long overall, which works FB down through 40 meters
(the effectiveness of a center fed wire doesn't drop appreciably until it
gets almost to 1/4 wavelength overall - or about 33 feet on 40 meters).

I arranged a 25 foot support pole just outside my shack window to hold it up
in the center. One end drops down to a support about 10 feet high and the
other end runs almost horizontally across to a point at the peak of my roof.

That combination works FB on 20 through 10 meters gaining me all the DX I
can hear - and that's a great deal when the bands are open. That length
makes the antenna an "extended double Zepp" on 10 meters, which is the
longest antenna one can use on 10 meters without getting into high-angle
radiation lobes. Of course, with the diminishing sunspot cycle 10 meters
won't be such a big issue except for those 10 meter enthusiasts who watch
for and enjoy the openings that occur all the way through the minimum.
They're there. They're just a lot less frequent than in the recent past.

As Stuart said, horizontal antennas are much more efficient than a vertical
because they don't have the ground losses that verticals have. That isn't
just losses due to a ground connection, but includes losses caused by
induction of ground currents some distance from a vertical that don't occur
with a horizontal.

But to provide low angle radiation for DX operations with a horizontal
antenna, you need to have it up close to 1/2 wavelength, at least, above the
ground. Lower heights will give you great high-angle radiation for
short-skip/local contacts out to perhaps 600 miles or so. That's what is
often called a NVIS (near vertical incidence system) today. So, for good DX
effectiveness on 40 meters you need to have your dipole up about 50 or 60
feet at least. For many ops, including myself in my present QTH, that's out
of reach. In that case, for contacts out beyond 1000 mi., a vertical, with
its inherent low angle radiation, can produce much better results in spite
of the ground losses.

What I do is to feed one half of my doublet - the half running almost 30
feet straight up the pole and then horizontally about 25 feet to the peak of
my roof, as an end-fed "Inverted L" on 40 and 80 meters. A 1/4 wave
counterpoise wire makes a good RF ground to load the "L" against (I used an
elevated counterpoise with a 'tuner' to resonate it for the band  I'm
using). That places the current peak of my antenna at the bend on 40, which
produces a heavy mix of vertical and horizontal polarization. Stations
within 1000 miles can't tell the difference between the "L" and my doublet.
Stations much past 1000 miles can't hear me on the doublet while they copy
me Q5 on the "L".

It also works on 80, although its short length really limits its efficiency
there. Still, I often work stations out to 1,000 mi on 80 running 100 watts
CW.  

I used the same technique Stuart mentioned to bring the wires into the shack
where I have a sash window by the operating desk. I cut a strip of expanded
foam about 1 inch high and as wide as the sash to fit tightly under the
window. A stick cut to length goes from the top of the sash to the top of
the window frame where it wedges to hold the window tightly down against the
foam (and keep the window from being opened from the outside). I picked up
some 1/4 inch plastic tubing at Tap Plastics that I poked through the foam
to provide "feed throughs" for the feeder and counterpoise wires. The tubing
is stiff and protects the foam from being cut and torn by the movement of
the wires. If I get too many holes from making too many changes, I just
replace the foam with a new strip. Very little air can slip through the
tubing with the wires in them. You can always add a dab of silicon grout or
a wrap of tape to completely seal them if desired. That results in very
little insulation efficiency loss with the thick strip of foam filling the
gap.

Like every antenna in every station, this one is a compromise. Perhaps mine
is more of a compromise than many, but it's less than many others have to
live with. And it works very well.

Ron AC7AC



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[Don Wilhelm-2]

Nicholas,

You can't get much better or more simple than a dipole.  Get it up as high
as possible and feed it with parallel line.  44 feet is a great length for
40 thru 10 meters and will do 80 meters in a pinch.  Can you get one end to
the peak of the roof?  That may give you the extra distance needed for a
straight run, but lacking that, fold the ends downward and get as much of
the full length up as high as possible.  The ATU will handle it fine - use a
balun at the shack - you may want to equip youself with both a 1:1 balun and
a 4:1 balun, the one that will work better depends on the band and the
length of your feedline, so you may have to experiment a bit with the shack
end of the feedline.

For portable operation, the same answer applies, but if you can find no
suitable supports, perhaps a vertical is the better answer - use a 22 foot
vertical wire or tubing and use one or more 22 foot lengths of wire as
radials.  Feed with parallel transmission line the same as the dipole and
you should have an effective antenna.

73,
Don W3FPR

----- Original Message -----
>
> My K2 is complete and I will finish the auto ATU tonight. I am sure this
is
> FAQ please feel free to refer me! So, here goes..
>
> What simple Antennas would you recommend for use with my K2 and the built
in
> auto ATU for
>
> 1. Base station use, a small back garden 30ft by 22ft? My "shack" is on
the
> first floor in a room facing the garden. At the moment I have no holes in
> the wall!! If I have to run wires around the window frame to start with
that

> is fine. Just keen to get going!!
> 2. Portable, by the seaside or in a pub garden?
>
> Thanks!
>
> Regards
> Nicolas
> www.m1hog.com
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.725 / Virus Database: 480 - Release Date: 19/07/2004
>
> _______________________________________________
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> You must be a subscriber to post to the list.
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http://mailman.qth.net/mailman/listinfo/elecraft
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> Elecraft web page: http://www.elecraft.com
>
>


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[Rich Ardolino]

>Subject: [Elecraft] RE: Effective Antennas for use with K2 ATU


Hello Nicholas,

Before you start drilling holes in your window frame, look here :
http://www.qsradio.com/Mounts.htm

Scroll down to item FTP-4/U-XL, the "PaneRelief" coax feed thru panel. It is
a nice way to run your coax (or twin lead "ladder line" or open wire feeder)
outside without drilling holes in wall or window frame. I bought one from
qsradio at a  local hamfest.... works great!  Its a simple enough idea,
could be easily homebrewed using the photos on the website as a construction
guide......or you could use  a piece of wood as a substitute for plexiglas.

Hope this helps....I'm sure you will get lots of advice about what type
antennas to try......you will be amazed at how well the K2s autotuner
works.....have fun with your new K2....I'm sure you will like it.

72 & Regards,

Rich  K2CPE
K2 #1102


> At the moment I have no holes in
> the wall!! If I have to run wires around the window frame to start with
that
> is fine.


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