[TowerTalk] Log Periodics

[alsopb]

I would say that both of these posts are in the realm of speculation.

There is no calculation for horizontal antennas I have done in
EZNEC/AO that shows much modification of the vertical pattern due to
antenna design with a few notable exceptions.  The exceptions are
extremely long "boom length" antennas.  By long, I mean 5 wavelengths
or more.  It may be possible to build such a LDPA so that at its
highest frequency the boom is this long.  However, the design's I've
seen for LPDA'S all have booms comparable to commercial yagi's.

If you guys would provide an LPDA model for EZNEC, I'd be glad to run
it and end the speculation.

73 de Brian/K3KO  



Peter Forbes wrote:
> 
> 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
> 
> >                          "Now you have the rest of the story."
> >
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> >
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