[TowerTalk] Was April Fools, now radiating dummy loads

[Mark Shaum]

Roger asks:

> But WAIT!  Didn't some company recently come out with a
dipole center
> connector that contained a large fifty ohm load resistor
across the
> coax terminals and the entire thing was sealed from
prying eyes.  The
> claim was that you could use this antenna on ALL BANDS
with ANY LENGTH
> OF WIRES and it would load beautifully!  I believe the
claim was
> accurate. I also believe the military bought loads of
them.  I only
> wish I were kidding on this one.
> 
> Please,  someone out there.... tell me it wasn't so or
please confirm
> what I'm saying is TRUE!
> 

I think it's been a number of years, but I believe that
statement is true.  I would think some government employee
or military technician would attempt to evaluate a sample
unit, but in this case, I'm not sure.  However, dummy loads
do radiate!  Put your Cantenna on top of your 100 foot
tower, and attach a coax tee.  Plug in a dipole resonant at
some frequency in the lower third of your coverage range. 
The efficiency is going to be pretty poor, but what the
heck, you are saving 3 db of loss in not using a tuner in
trade for about 3 to 20 db less radiated signal across the
coverage range.  No problem, just run 150000 watts output
and the far end won't tell the difference!  Probably
quieter on receive, too <grin>.

Reminds me of long ago days at W8UM when we worked a fellow
in one of the dorms about 2 miles line of sight when tuning
the 32S3 into a dummy load.  I think he gave us an S8 or
so.  Asked him to stand by while we tried a new antenna. 
Flipped on the 30L1 and switched to the 40m yagi which was
pointed in the appropriate direction.  "Hows the signal
now?".. hehehe

Seriously, there have been what I would call reasonable
attempts to make relatively efficient broadband shortened
transmitting antennas using resitive loading.  The T2FD
comes to mind as one that has seen more than a little use
over the years.  I believe the B&W folks are still
manufacturing a dipole and unipole (grounded end) version
of the T2FD.  And then there is my first novice antenna, a
Hy-Gain base loaded 18V with a three foot ground rod, no
radials, mounted a foot from a chain link fence.  With the
losses taken into account, that antenna qualifies as a (not
quite) radiating dummy load.  After two weeks of after
school CQ'ing, I finally worked a fellow in the next suburb
(15 miles or so) who gave me a 569C report for my first
QSO.  I was quickly instructed as to the advantages of the
simple inverted V, it's been a blast ever since!
 
Then there is the terminated V and rhombic class of
antennas, where you are more or less diverting power that
would radiate to the "rear" of the antenna into the
terminations, thereby gaining a unidirectional antenna. 
Ya, not exactly technically correct, but it settled well
when I gave a two session introductory antenna forum at a
new novice class back in Chicagoland.  



----------------------------------------
Mark Shaum  K9TR
mashaum@fcg.net
Central Illinois Grid EN50
---------------------------------------


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