AH6RH, Ron, provided the link info on the 'unusual' LPDA:
"That log periodic is unusual, in the sense that it is not just a flat LP
antenna like most installations. There is an LP on the top, angled
down, and an LP on the bottom, angled up. They meet at a vertex. I'm
not 100% sure of that particular design. My understanding was that it
was salvaged and reused from a military radio station."
You can see a similar antenna at this site. It appears to be a Collins
antenna.
http://jproc.ca/rrp/inuvik.html
-0-
This appears to be a variant on the original, patented, log periodic design
from Collins, which was sold to the government for multiple installations.
There was a TT thread about this a few years back, when I was considering
"stacking" two T8's in tilted fashion. The project was shelved after the
first T8 and my ab621 came under assault from a mighty oak.
It's easy to ping-pong phase such a stack, and picking the right tilt angle
can give you uniform stacking distance across the full octave. It's a
nightmare
to model, however, and I never got a chance to see the effect of the
close-spacing
(.25 lambda) on the in-phase/out-of-phase vertical angle.
In the case of the antenna at the inuvik link, I believe the complementary
halves
of each dipole are on the opposite boom, top to bottom.
N2EA
Jim Jarvis, President
The Morse Group, LLC
We create high-performance organizations.
732 548 5573 office
443 618 5560 cell
jimjarvis@themorsegroup.net
www.themorsegroup.net
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