[TowerTalk] Shadowing of small antennas by larger ones?

[n4kg@juno.com]

On Thu, 1 Feb 2001 "Al Williams" <alwilliams@olywa.net> writes:
> 
	SNIP
> 
> I have long wondered why the reflector on a yagi is longer than the 
> driven element and why the directors are shorter.  Also why do multiple

> directors increase the gain but multiple reflectors do not? I suspect
it has 
> something to do with the geometry and transit time but its only my WAG.
 
> Hopefully "several technically will-versed people" will enlighten us!
> 
> k7puc
> 

The simplistic answer is:

Reflectors REFLECT  

(very little signal continues past them to the rear
so additional reflectors offer little additional benefit)

Directors DIRECT

(they focus the signal foreward where additional
directors further focus the signal foreward).

Currents are induced in the parasitic elements
which combine vectorally with the current in the 
DE to produce the far field radiation pattern.  The
phase of those induced currents depends on the
length of the element.

de  Tom  N4KG



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