Topband: Elevated Radials

Tom W8JI w8ji at
Mon Mar 4 08:18:46 EST 2013

Grant and all,

The lingering problem with this, like with many other things in life, is 
that the time or effort required for good verification of a theory or idea 
is much larger than the time or effort to form and publish an idea.

The result is almost nobody actually verifies a theory in a way that 
quantifies the change. It all becomes personal belief, feeling, or faith, 
mush of which is often exaggerated far beyond what the change could really 
be. If you read carefully, you'll see articles that use the words "measure" 
and "build" , giving the illusion something was built and measured, when the 
"construction" is actually only model.

Another common thing is to measure something other than field strength, and 
conclude the thing measured indicates or verifies the supposed field 
strength or efficiency changes. Examples of this are:

1.) Making a "happier amount" of contacts

2.) Measuring current and concluding a field strength change

3.) Measuring base impedance and concluding a field strength change

> 1. I would think that a system with elevated radials that slope upward 
> towards the far ends (e.g for 160m 10' at feedpoint and 30' at far ends) 
> should have less loss as the field is less near earth where the voltage is 
> high in the radial. (unless there is something else that goes the wrong 
> way).

It depends on the soil, the number and length of radials, and the antenna.

> 2. Is 1/4 wl resonance at all important as the number of elevated radials 
> increases - eg 10 total?  The QEX N6LF papers seem to indicate that a 
> little less than 1/4 wl is optimum for that number of radials.

The more radials, the less critical and more repeatable everything becomes.

> As much as I try to get answers to these from EZNEC+ the far field results 
> are all the same, 4 or 10 elevated radials and sloping or not, resonant or 
> not.

That result probably is because there isn't the large change we expect in 
the real world. The only real problems with EZNEC are how it calculates very 
low angle patterns (infinite flat earth) and it treats earth as a 
homogeneous media.

> PS: if you have a moment please explain the pros and cons of skirt wires. 
> I think they are a good thing for top hat loading systems, but I can't 
> reason it out for elevated or in the ground radials. The old VLF antennas 
> all had them on the elevated ground planes, which isn't in any current 
> recommended practice.

The only thing skirt wires significantly do is change bandwidth. They can 
also change current distribution if the system is not top loaded and relies 
on capacitance of the vertical structure for loading.

Look at Rudy N6LF's clear published warnings about (mis)use of his data, and 
then look at how his cautions are ignored as people selectively use the data 
they want from his articles as absolutes.

73 Tom

More information about the Topband mailing list