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Old October 11th 05, 02:42 AM
Richard Harrison
 
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Jim wrote:
"What kind of antenna design could I switch to when I get to close range
that would have a narrower beam so I could pinpoint my target?"

J. Roy Smith, W6YA described what he called "the simplest of DF loops,
with no ambiguity of direction" in CQ magazine`s 1963 "Antenna Roundup".
Roy also called ot the "Nobaloop".

Roy said it was designed for locating signals on the 10-meter band but
has been used with reasonable success on the lower frequency bands. Roy
used the loop on 80 transmitter hunts winning first place 15 times when
many of his competitors were using identical loops.

The loop is about a 1-meter length of 1/4-in. dia.copper tubing (gas
line) bent into a neat circle. The two ends are flattened for about half
an inch in a plane perpendicular to the radius. Number 28 holes are
drilled through the flattened tubing about 1/4-inch from the ends. The
loop is attached to a coax receptacle such as Amphenol 83-IR or military
type SO 239. One loop end is attached to the outer conductor by a 6-32
screw through one of the four holes. The other loop end is placed over
the receptacle`s center conductor lug and soldered well.

The small loop gives a figure-8 response in the plane of the loop. The
attached coax distorts this pattern, adding its vertical response, like
a sense antenna. The resulting pattern is a cardiod.

Nearby vertical objects may need detuning to avoid interference with the
vertical loop.

The maximum lobe is about 30-degrees wide.

The null is about 5-degrees wide, according to the author.

I have not built it but it seems simple, small, and easy to duplicate.

Best regards, Richard Harrison, KB5WZI