[TenTec] Open Wire Line 1/4 wave dipole

[Rick - DJ0IP / NJ0IP]

Rob,

I'm going to comment on feeding the 1/4 wavelength dipole in the middle with
openwire.
And as you will see, it is not quite so bad as it is being described here.

BEFORE I DO THAT, LET ME BE CLEAR:  I AM *NOT* RECOMMENDING THIS.  
                       IT IS A BAD IDEA!

BUT SOMETIMES IT'S THE ONLY WAY SOMEONE CAN GET ON THE AIR AT ALL!
                     (any port in a storm)


Now to some facts:

In 1996, DL6RDR operated CQWW DX CW from my QTH.  He ran my Ten-Tec Argosy
in QRP mode and placed 2nd place overall in Europe and 1st place in Germany.
His only antenna on 80m was my 40m dipole fed in the middle with openwire. I
had a small 30' tower with a small beam for the high bands.

My yard was about the size of a postage stamp.  A 40m dipole just barely
fit.  There was no way to put up a full size 80m dipole, but I did not let
that stop me from putting together a winning contest station.  YOU DO WHAT
YOU HAVE TO DO.

It is fully appropriate to point out bad practices but just shaking your
finger at them does not help those of us who have no other alternative.

Rob hinted at what you have to do to use an antenna like that.
In a nutshell:  use oversized matchboxes.

In my case (the QTH above), I typically ran 600w into the antenna.
I was running a home-brew link-coupled symmetrical matchbox, using the
Annecke circuitry, which is a highly improved version of the old Johnson
Viking Matchbox.

We all read the same antenna books and should all be familiar with the
proper way to do things.
Feeding a dipole in the center, through a 1:1 balun, with good quality coax
is in all cases the best solution... when you want a good single band
antenna.  In a pinch it can work on its 3rd harmonic band.

Living conditions outside of the United States are very different.  In many
countries, people live on top of each other.  Many hams live in huge
apartment complexes and are lucky to have any kind of antenna at all.  

Germany, where I live, has the highest population density of any other
European country.
We have some countryside, but there are no jobs there.  In the cities where
the jobs are, there is almost no room for antennas.  As a result, we have to
get creative, or else we are QRT.

Here in Europe we have occasional magazine articles and even a few antenna
books describing all kind of small antennas that work in limited spaces.  Of
course their efficiency is low compared to full size antennas, but the OM
using them are grateful for every single QSO.

ONE MORE EXAMPLE:

I lived near Oklahoma City from 2007 until 2010.
Although I had a full size dipole on 80m, I also put up a 40m vertical
dipole, fed in the center with home-brew openwire.  It was actually 59 ft.
long, about 10% shorter than a 40m dipole.  So it was slightly shorter than
1/4 wavelength on 80m.

I ran this antenna in DX contests.
Running my Omni VI+ and 600w, I found I could work an DX station, any place
in the world on 80m.  Each time a new station appeared in the spotting
window, I jumped to that frequency and worked the DX with one or two calls
(occasionally 4 or 5 calls), through pileups.  Regardless of whether he was
in Africa, Asia, Pacific, whatever, I got through in short order.

SO PLEASE STOP TELLING PEOPLE THESE ARE BAD ANTENNAS!
Instead, warn them that they are dangerous antennas unless they do their
homework.

How about explaining to people how to use them?
That would add some value to the conversation which we cannot read in the
ARRL Handbook.

What was my ultra-secret complex matching solution for the vertical dipole?
A $300 used Ten-Tec Model 238 matchbox and a $25 home-brew ugly balun.
Oh, and I had to bolt an external capacitor to the terminals on the back.

You can view pictures of the antenna and station, here:
http://www.dj0ip.de/my-station/oklahoma-2010/ 
 
In one of his many articles, L.B. Cebik (SK) pointed out that antenna even
1/8 its normal size can still be a very efficient radiator, "if" we find a
way to match it efficiently.

How about some of the engineers picking up that ball and running with it,
rather than just repeating what we can read in a dusty old antenna book?
;-)

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Rob
Atkinson
Sent: Monday, October 19, 2015 11:51 PM
To: tentec at contesting.com
Subject: [TenTec] Open Wire Line

>Re-read my sentence. I am not objecting to the use of open wire line when
it is matched to the antenna, but to the use of it as a band-aid for badly
matched antennas.

I suppose it gets down to the meaning of "badly matched."   If by that
you mean for example a 1/4 wave dipole fed in the center then I'd say
nothing should feed such a load because it's pretty close to hopeless.
This is an antenna that will probably have an impedance of just a few ohms.
I have heard of hams building balanced matching networks capable of handling
20 or 30 amps for such an antenna but I'd put up a bigger antenna.

Most all medium wave broadcast stations have abandoned their open wire
unbalanced line.   KFBK in Sacramento still has it as far as I know.
They may be the last.  That line worked okay in the days of tube rigs but
the solid state boxes would kick off if a bird flew into the line and got
across the center and one of the outer lines.  they had to go to coax below
grade.  I am not against coax; I use it with unbalanced loads.

73

Rob
K5UJ
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