[TowerTalk] matching a delta loop
Jim Jarvis
jimjarvis at verizon.net
Thu Oct 19 16:19:52 EDT 2006
Sorry... with the apex UP...the feedpoint impedance
varies with the height of the lower leg above ground.
The ones I had were no more than 10' or 15' above gnd,
to produce a decent match. I'd have to check the literature,
but I think it specified .15 lambda elevation for the lower
leg. You can diddle the match by moving the lower corner
insulators, to shift the apex angle and lower leg length.
They worked ok...but not as well as a good GP, with
elevated radials.
As for the K8UR array, in contrast with a 4 square...
You can feed the k8ur array with 3/8 lambda coax, from
a center switchbox, with isolated shields. The unselected
dipoles act as a reflector. Not overly complex, as switching
goes.
Another possibility...you could put up a delta loop as a
reflector, and one foldback sloper each side of that.
Two directional choices.
Works very nicely on 160, at one of the sites I contest at.
Broad pattern, some gain, reasonable f/b.
n2ea
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