On Thu, 20 Mar 1997 12:15:23, John, N4JS, spake thusly and in part:
"I for one, am working on a multi-band 30/17/12M dipole!"
-- While thumbing through my old CQ rag collection, I came across a
tri-band set up that may be useful to some.
From CQ Feb 1995, page 94, by Bill Orr, W6SAI.
He called it an open-sleeve dipole, describes a good history,
rediscovered by K9AY.
The length would be 46' 8" long plus insulators and bridle. The
antenna is three separate dipoles, spaced 2 inches from each other,
with only the centre one fed, the other two being excited by close
proximity.
26' 0"
Separated by 2"
46'8"
Separated by 2"
18' 11"
I suggest that, if interested, you run down a copy.
-- My personal experience in this area:
In the late 80's I was putting up a communications system in Bermuda
and was rooming with my colleague, VE7QI, over the winter, on a farm
with plenty of room for antennas. The owner let us put up as many
antennas as we could manage (the company was paying her BIG bucks to
rent the whole place) so I rubbed my hands together and strung an 80
meter dipole from a Norfolk pine, up about 100 feet. Man, I really got
into Europe and back to HQ in Chicago. Earl, though, was trying to
figure out how to string a wire beam for 20, 15 and 10 in a nearby low
tree. He used a similar scheme to the one mentioned above by W6SAI and
positioned the 15 and 10 meter dipoles just inches from the 20 meter
driven element. While assisting him to build this bamboo and wire
contraption, I (otherwise known as "Mr. Antenna") said, "Earl, this
piece of crap is never gonna work! Why don't we just stick a vertical
on the roof?". Earl just looked at me and shook his head and while he
was walking away said, "I got a sked tonight with ZL somebody and I'll
need the rig for a while." He then proceeded to work ZLs with 100
watts that night and every night for a month. Earl later explained to
me that he called it "shock excitation" of the other dipoles and had
used this technique before in Africa, the Middle East and ZL land on
his many wire beams. I learned several lessons over that winter, not
the least of which was a certain humility.
Cheers,
-- Jakarta Mark K9AM at YB0ARN QRP-L #443 k9am@amsat.org
+---------------------------------------------------------+
Mark D. Anthony, Implementation Manager, L.M.P.S.,
Radio Network Solutions Group, Asia/Pacific, MOTOROLA Inc.
email: CFES03J@email.mot.com
Location: Jakarta, Republic of Indonesia
Time Zone: GMT+7 (13 hours ahead of Chicago)
Tel: +6221-574-5806 Fax: +6221-574-5817
+------------------- -.- ----. .- -- -------------------+
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