FYI, I have communicated a couple of days ago (6/9) with K1DFT regarding his
'DLM antenna' efforts. He was offered an opportunity to do some independent
range testing here in the Boston area. He stated that he is now testing at a
well-known facility (that I am familiar with). I understand he is planning to
talk at Boxboro in August (you may know this).
My thoughts below may be of enlightening to some. Frankly, this exhausts my
scientific interest in this topic. Boxboro will be fun though.
------------------------------------------------------------------------------
---------------------------
The prior art is rife with distributed loading of monopoles to extensively
shorten them.
Here is a prior art method that will gives a few percent bandwidth and about
-2 dBd (free space)for less than 1/15 wave height. I invite you to experiment
for values and placements:
* Take a half wave of wire (approximately);
* Wind it into a helix of about 10^-3 waves diameter (or less);
* Place an inductive load half way up;
* Add at least 2 and up to 6 capacitors at distributed points along the helix
length;
* If you wish to truncate the current at the top, then add a small end cap
hat;
Essentially this is a shrunken 1 wave dipole design manifest as a 1/2 wave
monopole, using CCD to neutralize the inductance.
This will 'linearize' the current and do a pretty good job.
HOWEVER--
* It will be moderate to narrow band;
* It will trade gain for efficiency and is NOT efficient;
* It will not be identical in gain to a 1/4 wave monopole;
* It will run hot in continuous on applications with moderate to high power.
Mr. Vincent's original PR claims, to my recollection: high efficiency; good
(broad) bandwidth; very low height.
These are not mutually, physically, attainable. I, and many others, have
spent enough time to know. There are many on this list who can vouch for that
also.
In terms of applications, there are very few, besides some 'ham' and CB
needs, where a single band, somewhat inefficient whip is desired. Midland has a
nice compromise stick available for CB'ers that's using some of these ideas and
is less than two feet high. I like their design.
--Using a heavily shortened CCD type monopole in a broadcast app will lead
to arcing and fire, IMO. Running a KW will also be potentially dangerous;
--Much of the world wants 'ground independent' antennas--not monopoles;
--Much of the world wants multiband antennas, or wideband antennas, not
modest passbands;
--All the world wants CHEAP CHEAP CHEAP:-)!
73,
Chip N1IR
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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