Thursday, March 6, 2014

Simple Ham Radio Antennas: Sam's "James Bond" Antenna. Post #264

Whenever I get a day off from my substitute teaching duties, I try to attend meetings of the Hawaii QRP Club at the Hilo, Hawaii Jack In The Box Restaurant.  The meetings usually last from 0600 to 0900 local time and cover a variety of topics, from antennas to homebrewed equipment.  Attendance varies from to 2 to 7 or 8 persons, depending on who's working or free for the day.  Dean Manley (KH6B) usually brings some of his antenna notebooks and his vast storehouse of experience as a radio broadcast engineer to the meetings.  There's always something interesting or new at these gatherings.

Recently, some of us have been discussing homebrewed antennas that can be operated from areas restricted by HOAs, CC&Rs, or just plain lack of space.  One of the most intriguing antenna ideas came from the late Sam Kumukahi (KH6AFS), who, during the 1990s, used what he called a "James Bond" antenna with excellent results for local and occasional DX contacts.  At the 27 Februrary 2014 meeting, Dean gave me a description of this simple, effective antenna which can be used at home or in a portable situation.  The information below was given to me by Dean as a one-page handout.

Sam's "James Bond" Antenna (excerpts):

Sam Kumukahi, KH6AFS (SK), has been routinely using the "James Bond" antenna.  Questions still arise:  What is it?  How high do I install it?  How long do I make the feed line?  First of all, when "Uncle Sam" says he's using an antenna just 31 inches, it's true.  Believe him!  After a few skeptics doubted the performance, Sam loaned me his "James Bond" antenna.  I had a problem getting it to work in the shack, probably because of inadequate ground.

I moved the 31 inch antenna and my antenna tuning unit (ATU) to the garage floor. It barely fits between the car and my radio shack door.  It loaded up just fine.  I checked into the Hawaii Afternoon Net on 40 meters.  Yes ,(I) came back (with) many favorable reports.  Jack, KH6CC (SK), said I was just as strong as my dipole antenna!  Yes, now I'm a believer.

Picture your ATU in your shack or maybe on a picnic table in a park.  Take the mobile loading coil and its adjustable upper radiator.  I use a Hustler on  40 and 75 meters and a homebrew one for 160 meters.  Others have described fixed and portable operations with the entire mobile antenna.  This is different. Do NOT use the lower mast section.  Now attach the antenna to your ATU with the following connectors:

Feedthru/adapter, SO-239 to standard
3/8" thread, Radio Shack 21-961.
M-348 inline right-angle adapter, Radio Shack 278-199.
Double PL-259, Radio Shack 278-192.

Tune up is quite simple and straightforward:  (A).  adjust antenna above the loading coil for minimum SWR with the ATU switched "out."  (B).  Then, if SWR is not acceptable, switch in the ATU and adjust for minimum SWR.  (C).  Do not adjust the upper part of the antenna with ATU in the line as you may get misleading results.  Repeat A and B if necessary.

In the shack or elsewhere, you need a ground connection.  A good RF ground is quarter-wavelength coaxial cable.  I use a length of RG-58, one for each band:  23 feet for 40 meters, 42 feet for 75 meters, and 86 feet for 160 meters.  The coax center conductor only is connected to the ground post of the ATU.  The coax far end is (an) open circuit.

Dean Manley, KH6B., July 1995.

On Monday, 03 March 2014, I built a similar antenna using 40 meter , 20 meter, 15 meter, and 10 meter hustler mobile coils, their adjustable upper radiators, my trusty Drake MN-4 ATU, a homebrewed clamp, a 6-ft/1.82 meters length of RG-8X coax to connect the rig to the ATU, and a coax "counterpoise" bundle consisting of #18 AWG speaker wire measuring 33-ft/10.06 meters, 16.5-ft/5.03 meters, 11-ft/3.35 meter, and 8.23-ft/2.51 meters.  I attached the "counterpoise" bundle to the ground lug of the Drake MN-4 ATU.  The system seems to to work well, with only slight adjustments needed to the Drake MN-4.  I've received some good local reports on 40 meters and a few mainland U.S. contacts on 20 meters.  I made these contacts from an outdoor picnic table in my backyard.  The homebrewed clamp held the mobile coil and its adjustable upper radiator.  The rig was my old Ten-Tec Argosy II running around 10 watts both CW and SSB.  My power source was a deep cycle marine battery charged by solar cells.  I can fit the entire antenna system, the Ten-Tec Argosy II, the battery, Drake MN-4, and the clamp in the back of my Odyssey van.  The antenna works and would be ideal for emergency or portable use.

Thanks to Dean Manley for his advice and guidance in this project.

RESOURCES:

Personal discussion with Dean Manley on 27 February 2014, 0800 local time, at the Hilo Jack In The Box Restaurant.

MFJ makes a similar antenna called the MFJ-1622. The MFJ product is a variation of a design first marketed by B&W in the 1970s.  This antenna uses a tapped coil, a short telescoping radio antenna, a clamp, and a counterpoise wire.

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Aloha es 73 de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.


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