[TowerTalk] 80m 4 square on uneven ground

[Jim Brown]

On 4/11/2025 11:48 AM, john at kk9a.com wrote:
> I did not consider that phased verticals may be like Yagi's where F/
> B is more easily effected by system imperfections than gain.

An important fundamental principle that helps us think about things like
this is that nulls/rejections in a pattern depend on the cancellation of
radiation from various elements of the array, which, to be deep, must be 
VERY nearly equal and very nearly 180 degrees out of phase at the 
frequency of interest in the direction of the null. THIS is how less 
than ideal details of layout/dimensions, etc affect the result. 
Differences from ideal can be 20 dB or more.

Arrays are FAR more forgiving about additions in the pattern -- i.e., 
forward gain -- because moderate variations in the phase and amplitude 
have far less effect. Differences from ideal are usually a few dB, 
directivity can be skewed.

Example: I have a 2-el wire 80M Yagi rigged between two pairs of tall 
redwoods. The location of suitable trees results in the two elements, a 
driven and a reflector, being ~ 20 degrees out of parallel, and the 
heights of the two elements are ~120 ft and ~100 ft. My objective is 
forward gain to EU and the east coast of the US from my QTH south of San 
Francisco, and reversible to VK/ZL. If the elements were parallel, I'd 
get something like 4 dB; the angular skew broadens the pattern, reducing 
peak gain by about 1 dB. The difference in height affects the vertical 
pattern slightly. I don't care about F/B, because I have effective RX 
antennas in both directions.

This Yagi is my variation on an idea from a ham in SoCal, who rigged two 
80M dipoles low enough that open wire line to the ground was a 
half-wave, where he added reactance to set the phase of the reflection 
to produce gain. My dipoles are much higher and fed with RG11 (because 
they are high), so the phase of the reflection is set by switching in 
the "right"  stub in the shack for CW or SSB. Loss in the RG11 (~ 
160ft), gives up a large fraction of a dB of gain.

73, Jim K9YC