[TowerTalk] Log Periodics

[Peter Forbes]

K7GCO writes:
 
> Cheers,    Steve    K7LXC >>  This is very true but there is another 
>variable.  IF THE HORIZONTAL PATTERN IS WIDER, SO IS THE VERTICAL PATTERN and 
>this fills the higher angles with far more RF than the loss of gain and at 
>certain times of the day do a bang up job on DX also.  This is comparible to 
>a 2 element quad at say 1/2 wave or slightly higher do so well.  It's the 
>lack of gain that makes it work closer to the ground.  High gain beams don't 
>work well close to the ground.  k7gco 
>

Is it NECESSARILY SO that a wide horizontal pattern means a wide vertical
pattern as well?

The vertical pattern for a horizontal log periodic array is a function of
several things:

(1) ground reflection effects
(2) ground impedance effects (when within one wavelength height above ground)
(3) the spacing of the elements within the log cell which are active at that
frequency (in other words the Design parameter of the array (tau) and the
relative element spacing constant (sigma)).

In all my literature searches on the log periodic (both amateur and
professional) there is little discussion of the effect on the vertical
pattern when near the ground, with most computer modelling being free space
situations.

Cheers

Peter   VK3QI  ( an 18-29 mhz log periodic user)


S IT NECESSARILY SO THAT A WIDE HORIZONTAL PATTERN 



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