[Towertalk] tilted LPDAs

[Bob Nielsen]

It has been about 35 years since I have done any work in this area, but
I recall that the type of "tilted" antenna described was generally
referred to simply as a log-periodic array, not a log-periodic dipole
array. A number of the early log-periodic antennas used elements with a
geometry similar to a half-dipole, but the width, as well as the length
increased proportionally with wavelength (in some cases, the element
thickness did likewise, but normally these were two-dimensional,
leading the elements to often be referred to as "teeth".)

IIRC, the LPDA where all the elements lie in a single plane (or two
parallel planes), fed by parallel booms does not have quite as much
bandwidth as some of the other geometries which have been used for
quasi-frequency-independent antennas, since not all of the dimensions
scale with frequency (~5:1 or less, compared to >20:1 in some cases).

73, Bob N7XY 

On Wed, Mar 20, 2002 at 07:16:28PM -0500, Joe Reisert wrote:
> Hi Jim,
> 
> I hope we haven't been confusing things with the so called tilted LPDA's.
> 
> LPDA design is quite different than Yagi design. Each element is split and 
> there are two hot booms placed in the same plane (parallel to each other). 
> One side of the split element connects to one boom and the complementary 
> one to the other boom and then alternated as you proceed down the boom. I'm 
> sure we are all familiar with that approach which is the common type of 
> LPDAs we use nowadays.
> 
> However, in the early days (1950 through 1960's) of LPDA design, some of 
> the first designs used hot booms were often placed with a 30-45 degree 
> angle between them (instead of parallel to each other). The elements were 
> still connected as above. However, as you proceed away form the feed point, 
> the matching complementary pairs were placed further apart. This gives the 
> appearance of stacking.
> 
> I hope the above is clear.
> 
> 73,
> 
> Joe, W1JR
> 
> 
> At 11:55 AM 3/20/2002 -0600, James H. Fitzpatrick wrote:
> >I saw the tilted LPDAs near Champaign in August 1982 when I drove by while
> >moving to California. I wondered then what it was all about. Now 20 yrs
> >later I found out.It pays to subscribe to towertalk ;>)
> >
> >Jim
> >
> >WI9WI
> >
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-- 
Bob Nielsen, N7XY                          nielsen@oz.net
Bainbridge Island, WA                      http://www.oz.net/~nielsen
IOTA NA-065, USI WA-028S