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Reply-To: "Ron D'Eau Claire" <rondec at easystreet.com>
From: "Ron D'Eau Claire" <rondec at easystreet.com>
To: <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Four Band K1 and antenna
Date: Mon, 27 May 2002 13:38:36 -0700

> Just wondering what kind of portable antenna anyone uses when they are out
> portable in the field.
>
> I have the bands of 40, 30, 20 & 15 meters. Looking at a doublet type
> antenna, no verticals.
> Ron Polityka
> WB3AAL

Doublets are great antennas, for either fixed or portable use.

If you do NOT have an ATU (either the KAT1 or an external ATU), a half wave
on each band is the easiest to feed with 50 ohm coax. The 40 meter doublet
works okay on 15 in most cases where it is 3/2 waves long.

If you have an ATU, by all means put up whatever you can and feed it with
open wire line - ladder line is a LOT easier for portable use and darn near
as good. 300 ohm "twinlead" will do if that's all the volume you can take
into the field and it will still be superior to any coax when the SWR is
high.

Your radiator can be as short as 33 feet and still work almost as well as a
full sized 66 foot antenna on 40. The difference is less than 1/2 of one dB.

The big thing with a doublet is getting it up high enough if you want to
work DX and you are on level ground. Something between 3/8 and 1/2
wavelength is needed for good low angle radiation.

IF you are "mountain topping" or near a steep cliff, you can mount the
doublet so it is off to the side of the cliff. Some ops use a single pole
supported by a back stay holding it out near horizontal sticking out
perpendicular to the slope with the antenna hung as an "inverted V" from the
pole. The earth behind the antenna makes a great reflector that will produce
very good low angle radiation in the direction away from the cliff.

The optimum height above the ground for using the earth as a reflector is
about 0.2 wavelengths, although the height is not critical as long as it is
less than about 3/8 wavelength. If the antenna is really close to the ground
(< 0.1 wavelength) you will start to lose some signal due to ground
absorption, but you will still keep the low angle of radiation off of the
side of the cliff.

When calculating your height when it is hung as an "inverted V", use about
80% of the center height.

If you want to work relatively short skip 600 - 800 km (out to about 500
mi.) on 40, you will do best to place your antenna about 0.2 wavelengths
above the ground on level terrain. That produces a powerful lobe straight up
that gives you great 'short skip' contacts. Some ops working from
mountaintops have found it very hard to work stations less than 1000 km (600
mi.) away until the put their doublet on the very top of  the ridge and kept
it low to the ground. BTW, this sort of installation has the current
nickname NVIS antenna for "Near Vertical Incidence System". You may have
seen articles about them recently. They've been the mainstay (and bane) of
hams working short skip or stuck with low supports since the wavelengths
below 200 meters were first explored, but they seem to have been
'rediscovered' with great fanfare by many hams recently.

Of course, these doublets require balanced feed, although they will work
quite well without it in many cases. Without balanced feed, the feeders will
radiate as much as the "flat top" and you will have a lot of vertical
polarization, assuming your feeders go straight up. Also, you want to be
sure your feeders are in the clear and go up as directly as possible, to
avoid losses coupling lots of r-f into other objects. For balanced feed so
your feeders do not radiate, you can get away with using a balun  between
the balanced feeders and the single-ended ATU in most cases, although it is
not uncommon for some bands to present such a high or low impedance at the
feedpoint that the balun acts more like a dummy load than a balun. Still, a
decent balun works more often than not.

Finally, you mentioned that you were NOT interested in a vertical, but you
can also feed a horizontal antenna at one end just fine! That may be easier
with the KAT2 or most ATU's designed for unbalanced feed. Simply throw out a
1/4 wave long 'counterpoise' wire attached to the case of the rig to provide
an 'r-f ground'.. Some multi-conductor wire with sections cut to each band
work well. The trick here is to try to get your radiator close to (but not
exactly) 1/2 wavelength long. That will raise the feedpoint impedance which
vastly reduces losses in the "ground" connection or counterpoise. If you
made the radiator exactly 1/2 wave long, electrically, on our lowest band -
40 meters - the system will be the most efficient but the KAT1 and most
ATU's cannot handle the high impedance the antenna will present. So you want
to find a length that gets you close, but not exactly on the 1/2 wavelength.
Of course, 30 meters will be way off the mark, but it should work well
anyway. As you go up in frequency, the impedance at even the current loops
will raise, making the system more efficient in any case.

The "end fed" wire requires that you get it right up and in the clear, but
it eliminates the need for a separate feedline.

Good luck.

Ron AC7AC
K2 # 1289

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Date: Mon, 27 May 2002 15:52:37 -0500
To: "Ron Polityka" <wb3aal at fast.net>, Elecraft at mailman.qth.net
From: Jim Gelbort <jamesgelbort at worldnet.att.net>
Subject: Re: [Elecraft] Four Band K1 and antenna

Ron,

Two setups work for me:

With the KAT1 installed I have been quite happy using an endfed wire plus 
counterpoise.
As much wire tossed as high as you can get it, avoiding 1/2 wavelengths. 
For a counterpoise, I use two lengths of 4-conductor ribbon cable, with the 
individual wires cut to 1/4 wavelengths. This may be overkill.

Pre-KAT1, I frequently used a 44' doublet through a BLT tuner. Flat-top or 
inverted-vee mounting. Also worked well, but nowhere near as convenient as 
the endfed wire.

Hard to go wrong either way, especially for portable use.
72,
Jim Gelbort N9WW

At 03:42 PM 5/27/2002 -0400, you wrote:
>Hi,
>
>  I have been working on my antenna for the K1 over this holiday weekend.
>
>Just wondering what kind of portable antenna anyone uses when they are out
>portable in the field.

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Reply-To: "bob baxter" <rbaxter at cybertrails.com>
From: "bob baxter" <rbaxter at cybertrails.com>
To: <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Four Band K1 and antenna
Date: Mon, 27 May 2002 14:32:14 -0700

Ron,
I use a half sized W6RCA No-Tuner doublet with tuned twin lead feeders
for each band.  You can see it at
http://www.qsl.net/dl9meu/Antennen/ant-draht.html
I put it on a DK9SQ mast in an inverted vee.  It works great for me.  I
have one put up permanently at home but haven't got around to installing
the relays yet.  For field use I plug in the length of feeder I need
for each band.  It helps if you have an antenna analyzer to help cut the
feeder lengths.
Bob Baxter AA7EQ
Bisbee, Az.

>  I have been working on my antenna for the K1 over this holiday
weekend.
>
> Just wondering what kind of portable antenna anyone uses when they are
out
> portable in the field.

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Reply-To: "Don Wilhelm" <w3fpr at peoplepc.com>
From: "Don Wilhelm" <w3fpr at peoplepc.com>
To: "Ron Polityka" <wb3aal at fast.net>, <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Four Band K1 and antenna
Date: Mon, 27 May 2002 21:12:01 -0400

Ron,
If you are looking for simplicity without the need for a tuner, I would
suggest paralleled dipoles.  They can be strung up as either a horizontal
wire or as an inverted vee when only one support is available.

One caution -- I have had a variety of headaches with parallel dipoles
unless I provided a goodly amount of separation between the dipoles for each
band.  With the dipoles close together, I have found so much interaction
that cutting to the proper length is very difficult to nearly impossible
(the lowest band is no problem).
My favorite installation for parallel dipoles is to use entirely separate
wires for each dipole, and hang them as an inverted vee - and separate them
as best the environment will allow - for 3 dipoles, I would try to separate
each wire by 60 degrees.  Using the dipole wires as guy wires for a central
support pole works FB when there are no natural supports available.

If you are not really concerned about the pattern of radiation, I would
recommend no balun for portable operation, but a 1:1 balun at the feedpoint
of the dipoles works fine too.  I imagine that in a portable situation, your
choices for antenna orientation are dictated by the environment rather than
trying to place the max radiation in a particular place.  At QRP levels with
coax feed, the chances of having an "RF in the shack" problem are slim - I
have never experienced any problems, and I do not use a balun for my
portable antennas - it just makes them heavier.
73,
Don Wilhelm  - Wake Forest, NC   W3FPR home page: http://www.qsl.net/w3fpr/
  QRP-L # 485   K2  SN 0020   mailto: w3fpr at arrl.net

*** Life is what happens when you're making other plans -- Mike Cross  ***

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Date: Mon, 27 May 2002 23:53:56 -0400
To: "Ron Polityka" <wb3aal at fast.net>
From: Charles Greene <W1CG at QSL.net>
Subject: Re: [Elecraft] Four Band K1 and antenna
Cc: <elecraft at mailman.qth.net>

At 03:42 PM 5/27/2002 -0400, Ron Polityka wrote:
>Hi,
>
>  I have been working on my antenna for the K1 over this holiday weekend.
>
>Just wondering what kind of portable antenna anyone uses when they are out
>portable in the field.
>
>I have the bands of 40, 30, 20 & 15 meters. Looking at a doublet type
>antenna, no verticals.
>
>Thanks for any input.
>
>72
>Ron,


The last "outing" I used a 40 meter OCF, but it used two DK whatever 33' 
collapsible fiberglass masts; mine and K1JD's.  The long 45' part was 
between the two masts, and the 22.5' part came down like an inverted 
V.  Then I modelled it in EZNEC and decided I didn't like the 
pattern.  Most of the radiation patterns were of figure 8 type except for 
40, and we didn't use 40.  So pattern wise, I decided to use an extended 
double Zepp on the highest frequency used which probably will be 10 for our 
next outing.  (You would use 15).  It will use one 33' mast and be 
installed inverted V type.  Nice gain on 10, and it gives a broad side 
pattern on all other bands and gain pretty close to a dipole.  Just feed it 
with open wire.  I use some home made from #26 silver plated, stranded, 
teflon insulated with a slight twist or held together close space with a 
1/8" piece of heat shrink tubing every 6".  I calculated it has a series RF 
resistance of about 5 ohms for a 37' length, and an impedance of about 180 
ohms, but that's not the point.  It is low loss and with a balun, the KAT2 
loads it up fine on all bands including 80.  Light and easy to carry 
compared to 300 ohm ladder line and a lot less lossy than RG-174.  Just 
thought I would share this idea.



73, Chas, W1CG

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Date: Thu, 17 Oct 2002 15:28:00 +0200
Organization: http://freemail.web.de/
From: Christoph Rheker <dl4yao at web.de>
To: elecraft at mailman.qth.net
Subject: [Elecraft] Antennas etc..

There are some good sites to read:

"how to become an antenna guru"
http://www.borg.com/~warrend/guru.html

W4RNL with both practical info and background, excellent:
http://www.cebik.com/

Lots of info can be found in the discussion archives on contesting.com:
http://lists.contesting.com/_towertalk/

I am sure there are many more.

73, Chris DL4YAO

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Date: Sun, 23 Feb 2003 22:11:19 -0800
To: elecraft at mailman.qth.net
From: Larry Weaver <n6tw at n6tw.org>
Subject: [Elecraft] Antenna Musings (was EH antenna...)

At 09:59 AM 2/23/2003, you wrote:
>.....
>I am NOT suggesting that people who hook up a new antenna and work
>fantastic DX with it are lying, but I am saying that the "real world" is
>too variable to collect valid data about one antenna being better
>without carefully-controlled conditions where antennas can be compared.

During my working life, I dealt with antennas at frequencies where testing 
in an anechoic chamber was possible. Even in such a highly controlled 
environment results were sometimes questionable. When the antenna was put 
in its real environment, it usually performed differently. We can approach 
that kind of test with field strength measurements much like those 
performed by the HFPack group (http://www.hfpack.com) who seem to be using 
a good method although I haven't looked at it in detail as yet.

Most amateur radio antenna comparison is anecdotal (especially in ads), not 
scientific, which is OK so long as it's not confused with a definitive 
answer. "I worked the world on my Gotham vertical." (Remember the Gotham 
vertical?)

An example of anecdotal performance is my experience in the ARRL 160 meter 
contest in December. I live on a small lot which makes a 160m antenna 
problematic. Fully subscribing to the idea that "any antenna is better than 
no antenna," I put up an inverted-vee, of sorts, which was 30 feet high in 
the center with most of it wrapped around the house at eave level. I was 
able to work the east coast and Hawaii from Southern California. Sunday 
morning, I got up and made several more QSOs, one in Texas. Being a 
temporary installation, I went out to take the antenna down only to find it 
had fallen down during the night. Those final QSO"s were made with the wire 
laying on the ground. I suppose I could sell it as a stealth 160 meter 
antenna at a huge price since I have confirmed QSOs saying it 
works--"works" being a relative term.

The antenna's environment is an important factor. Many of us probably dream 
of huge Yagis on tall towers. Yet the experience of Team 
Vertical  http://www.k2kw.com/  says a vertical in a salt water environment 
beats a Yagi. Is a vertical better than a Yagi? Not at my location on a big 
chunk of limestone in So Cal but it is on Palmyra Island or the right 
location in Jamaica.

Another variable is what you want to accomplish with the antenna. Until new 
laws of physics are discovered, the bigger and higher the better, as Ron 
said--up to a point. For antennas small relative to a half wave (or 
quarter-wave for a monopole vertical), that is definitely true. The low 
radiation resistance combined with losses in the matching system leaves 
little power radiated. A 20 meter ham stick is consistently better than the 
Yaesu ATAS on my vehicle. On 15  & 10, they are comparable but not as good 
as a longer antenna.

An antenna can be too long. When an antenna reaches multiple half-waves in 
length, nulls appear in directions that may be important to you. Oriented 
properly, however, it can have gain. Although it has the reputation of 
being a multi-band antenna, the G5RV was designed to provide gain on 20 
meters (see G5RV's article in ARRL Antenna Compendium One) where it is 1.5 
wavelengths long. It's multi-band character is a result of the low loss in 
the open wire feedline used for matching on 20.

An antenna can be too high, depending on ionospheric conditions--that's why 
the "big guns" have stacks of Yagis that can be switched into different 
configurations. Sometimes the lower Yagi works better than the higher ones. 
NVIS antennas are an example of a low antenna (10 - 20 ft) which will 
perform better than a very high antenna out to 500-1000 miles.

A "best" antenna doesn't exist in a global sense; what is best depends on 
your QTH and what you want to accomplish. The best antenna is the one that 
radiates the high percentage of the power you put into it in the directions 
you want it to go. This is especially important when you are operating QRP.

Take a look at "Rules of Thumb for Beginners" 
http://www.fix.net/~jparker/norcal/features/bgnsant.html  and L. B. Cebik's 
pages http://www.cebik.com/radio.html  (especially "Antennas from the 
Ground Up" near the bottom of the page) which is filled with antenna 
comparisons using NEC analysis.

In most cases a Home Depot special will outperform many very expensive 
commercial antennas using gimmicks to attract customers, small size, and 
claims without proof. My favorite portable antenna is a 20 meter dipole 
made from a piece of 300 ohm twinlead that I saw in QST several months ago. 
By adding pieces of wire to the ends I'm on 40 or 80 meters. It rolls up 
easily and away I go. It works better than a commercial product I own and 
its price was one-hundredth the cost of the commercial antenna.

73...Larry N6TW

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Date: Wed, 19 Mar 2003 12:17:42 -0500
From: MaddogCLC at netscape.net (Christopher L. Cowan)
To: elecraft at mailman.qth.net ("Elecraft")
Subject: [Elecraft] antennas

For those of you inteested in small antennas there is a great on line magazine you can subscribe
to which offers much technical and practical info on a variety of antennas.  Go to :

www.antennex.com

I subscribe and have found the articles and the e-books they sell very interesting.  The
contributors are really on the cutting edge of antenna theory and design.  Their mission is to
find small antennas that really work.

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