Topband: NORD and UG top loaded antennas

[Tom Rauch]

> I have the US patents on the NORD vlf antenna and also some suggested
> design info for the NORD and UG antennas on 80/160 (from the Vertical
> Antenna Handbook)

Hi John,

They issue patents for anything, including things that never actually 
work as claimed.
 
I looked at my Vertical Handbook, and I have to say the section on 
small antennas was the first disappointing thing I ever noticed in 
"The Vertical Antenna Handbook".

The truth is really very simple. With a given physical area, the ONLY 
way to maximize efficiency is to make current as large and uniform as 
possible over the maximum available (vertical) distance. You do NOT 
want to fold the antenna back on itself. You do not want to use 
linear loading. 

To maximize performance, the only solution is to end-load the antenna 
with a large hat or some other form of termination that does NOT 
return to earth. Multiple drops do not help, and certainly multiple 
drops with multiple capacitors won't help! 

The only thing fancy shunt tuning or multiple drop wire stuff does is 
make the feedline see a new impedance. And you could do the same 
thing with less loss with a simple coil, matching system,  or 
impedance transformer.

The way we improve efficiency and reduce loss is with a top-loading 
hat. If the hat is large enough to dwarf the distributed capacitance 
of the vertical, we can place a high-Q loading coil anyplace in the 
vertical and efficiency will remain essentially unchanged. As the hat 
is smaller, coil placement becomes more critical.

If we replace the coil with linear loading, efficiency will never 
improve and in fact almost always is reduced. Linear loading is a 
marketing tool to sell antennas, not a solid design concept.

A linear loading stub of reasonably large copper wire providing 200 
ohms of inductive reactance has a Q of somewhere around 50-100. I can 
wind a coil on an old cereal box and have Q's higher than that, which 
means it would also have less loss!

So here is what you do.

Put in as many straight radials as you possibly can, bend them as 
little as possible. Tie in fences, pipes, heating ducts, or anything 
else you can connect to with the ground system. Spend the bulk of 
your time and energy creating the most solid electrical mass you can 
in the area you have to work with.
     
Use as much vertical section as you can. Install the largest ground 
system you can manage. Either use a mast with a very large hat on 
top, a T, or an Inverted L and make up any additional loading with a 
good air-insulated inductor with proper turns spacing as high up in 
the vertical section as you can manage. 

Match the feedline at the base with a shunt coil, and play with the 
ratio of turns in the loading and shunt coil until you are happy with 
the SWR.

Once you do this simple basic recipe, there is nothing else that can 
be done that will ever be any better in the same small area.    73, 
Tom W8JI
W8JI@contesting.com