[TowerTalk] 80 Meter Delta Loop

[Jim Brown]

On 7/23/2024 2:48 PM, RVZ via TowerTalk wrote:
>   Please advise if there would be much advantage with replacing my 80-m.
> Inverted Vee with apex at 100' AGL with a full-wave 80m. Delta Loop with
>   apex at the same height and fed at the top? Note: I realize the Delta
> Loop would have a lower angle of radiation if it was fed at a bottom
> corner but that isn't possible at this QTH.

NEC modeling should give the answer if you enter the soil parameters for 
your QTH. I've found NEC to be quite accurate if the model accurately 
describes the antenna.

One VERY important part of correctly comparing the antennas is to save H 
and V plots of their patterns, then import them on corresponding plots 
of the other antenna. This will cause the amplitude scale to be the same 
for both antennas. Otherwise, we're fooled by the so-called "take-off 
angle," which is a terrible way to describe an antenna.

One of the most common fallacies promoted by "take-off angle" is that a 
ground-hugging horizontal dipole is optimum for NVIS. Reality is that 
the optimum height of a horizontal dipole for NVIS is a quarter-wave.

For an example of what I'm talking about, study this modeling study I 
did about ten years ago. NCJ wanted to publish it, but the publishing 
folks at ARRL nixed it because there was too much graphics (which was 
absolutely necessary to show the result)!  Here's the NCJ piece.

73, Jim K9YC

http://k9yc.com/AntennaPlanning.pdf