[Antennas] vertical dipoles

[Cletus W Whitaker]

de WB2CPN South Central Pennsylvania   2002.07.15

The picture of the 15 MHz WWVH antenna was a surprise, something I
never expected to see.  There is nothing new under the sun...

Back in 1954 while I was stationed with the USAF in Alaska the
Communications Engineering group that I was in was requested (?) to
do something to enhance the communications between Elmendorf AFB
near Anchorage and the "Loon" Weather Recon flights which went all
the way to down to the end of the islands past Dutch Harbor, then
west almost to the Russian No-No line, then back up to Nome,
then to Fairbanks, then home to Elmendorf.  They used a 13 MHz
frequency, and a 6 MHz frequency, mostly.  The airplane used a
trailing wire antenna, so the polarization was skimpy at best.
What we came up with was called a "Moose Catcher".  For the 13 MHz
antenna we started off with a tall wood pole which had a wood frame
on the top.  This wood frame supported 8 vertical wires spaced 
about 4 feet across the diagonal.  These 8 wires came down the 
sides of the pole 1/4 wave (234) where they were tightened to a
frame similiar to the one on the top.  So we had a rather thick
1/4 wave if you consider the length to width ratio. Now, at the
bottom of these 8 wires, (they were joined at the bottom and 
connected to a L/C tuner because we used 600 Ohm open wire
transmission line), we formed a cone by running 36 1/4 wave wires
from the base of the 8 wires to insulators which were about 2 feet
off the ground.  The wires sloped at 45 degrees.  They were joined
at the apex of the cone, but not at the bottom.  Moose Catcher? Yep.

These antenna, funny as they were, performed better than any thing
else we tried.  We did learn that the polarization of the airplane's
signal did depend on the direction it was taking.  Horizontal
antennas, (delta match 1/2 waves) worked if the airplane was moving
broadside to the distant station. but wouldn't work if the airplane
was moving straight toward or away from the station.

Anyway, the idea of Moose Catchers must have caught on.  73  Clete