Topband: INV-L Radiation Patterns: 15 years of experiments with one L, one tree, and 3 acres.

[Jim Brown]

Multiple misunderstandings here. First, the earth is a big resistor, so 
the only function of that ground rod is lightning protection, and it 
ought to be at the shack, not at the antenna.

Second, the function of radials is NOT to couple to the resistive earth, 
but the SHIELD the antenna's field from the lossy earth, and to provide 
a low resistance path for return current.

Third, SWR is NOT a measure of antenna performance.

Fourth, the feedpoint Z of a vertical at resonance is a function of its 
vertical height. That Z is a combination of loss in the return (radials, 
counterpoise) and the radiation resistance; radiation resistance 
increases with vertical height, starting out quite low for short 
heights, reaching values in the range of 30 ohms around a quarter wave. 
For low heights, ground losses combine with radiation resistance to 
yield low SWR. Adding radials and/or increasing height can reduce SWR, 
then as more are added, increase SWR again.

There's a discussion about all of this in this set of slides for talks 
I've done at Pacificon, Visalia, and to several clubs.

http://k9yc.com/160MPacificon.pdf

Again, SWR is NOT a measure of antenna performance. Neither is how much 
DX we work -- that's far more dependent on propagation, and on RX noise 
at both ends of the QSO.

73, Jim K9YC

On 1/15/2024 11:13 AM, W3HKK at roadrunner.com wrote:
> But based on 15 years of reading and personal observations with my 1/4
> wave INV-L ( that has grown ( vertically through a black walnut tree)
> from 15 ft tall to 52 ft tall, and from one ground rod and zero
> radials to the same ground rod and 26 radials, here is what I can say: