[Elecraft] Off-Topic: Your advice/suggestion about antenna

Jim Brown jim at audiosystemsgroup.com
Fri Mar 13 17:02:32 EDT 2020


On 3/13/2020 12:49 PM, Lyn Norstad wrote:
> I actually do consider 4.7 dbi as "far outperforming" 2.14 dbi (ordinary dipole).

It depends on what you want to achieve. The antenna you describe is a 
very old and well accepted design. It's like a beam with a fixed 
direction. No question that 2.6 dB can matter under marginal conditions. 
I have a 2-el wire 80M Yagi fixed on about 45 deg az that I can reverse 
to VK/ZL, which modeling shows gives me about that directivity.

HOWEVER -- in this applications note, I showed that raising a 40M or 20M 
dipole by 15 feet will also increase gain at low angles by about 2.6 dB. 
See Figs 33 and 41, and the associated text. Doing this uses height to 
modify directivity in the vertical plane, without narrowing the 
horizontal beamwidth.

http://k9yc.com/AntennaPlanning.pdf

In the same app note, I also showed that mounting an HF vertical on a 
roof reduces ground losses and increases gain at lower vertical angles 
(below 30-40 degrees) than ground-mounting it. The differences show up 
for all soil conditions (except sea water), but are most pronounced for 
poor soil.

I showed that the gain of vertical antennas is strongly affected by soil 
conductivity, while horizontal antennas are not, but are strongly 
affected by mounting height.

And finally, I disproved the myth that antennas must be low for NVIS, 
that 75 electrical degrees is optimum, and that raising it to 120 
degrees reduces high angle radiation by only 1 dB while increasing low 
angle radiation by 6 dB.

Antennas are the component of our stations that are most strongly 
dependent on operator goals, real estate, the availability (and the 
cost) of suitable skyhooks or towers, their ability to reject local 
noise, and restrictions like HOAs, neighbors, and XYLs. No single 
antenna is best for all stations or operators. Antennas I can rig here 
in my redwood forest would be impossible on the city lot I owned in 
Chicago. :)

73, Jim K9YC




More information about the Elecraft mailing list