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A Three - Element Yagi Mini-beam
Using "Hamsticks" For 20 Meters
Got some spare "Hamsticks" laying around?
Put them to good use and EXPERIMENT!
(Published with the kind permission of Russ Wilson VE6VK firstname.lastname@example.org)
who is totally responsible for all your fun with this project! Thanks Russ
(Article edited from the original slightly)
Rick NE8Z and I were having a very long discussion about minibeams and credit for suggesting the use of hamsticks must go to Dr. Rick. I thought it was a great idea and well worth building one. I needed something light, easy to install and reasonably efficient with some directivity. Almost immediately I started building the boom and the feed point insulator and then ordered the hamsticks. After lots of experimenting the results are shown below.
BOOM = 12 feet (365.76 cm) x 1-1/4"(3.175 cm) diameter aluminum tubing [4' sections, (121.92 cm)]
Boom Element Spacing:
Driven Element to Director spacing = 5' 9" (175.25 cm)
Driven Element to Reflector spacing = 6' 3" (190.5 cm)
Dimensions From Boom To Tip of Hamstick Rod:
Reflector = 7' 6.5" (230 cm)
Driven Element = 7' 2" (218 cm)
Director = 6' 9" (205.5 cm)
DIMENSIONS OF HAMSTICK ROD (WHIP) FROM END OF HAMSTICK COIL:
Reflector = 3' 8.3" (112.5 cm )
Driven Element = 3' 3" (98.5 cm )
Director = 2' 10.4" (87.5 cm )
Impedance using omoga bridge:
48 ohms at 15 feet off the ground.
FEEDING = 1 wavelength of RG58U and a 1:1 balun
FREQUENCY COVERAGE = 14.070 to 14.295 flat
TOTAL WEIGHT (INCLUDING CARRYING TUBE) = 12 lbs.
Note: I color code my Hamsticks for ease of assembly. Also for further information on the mounting of the elements to the boom look below the large photograph
Since there are several different "Hamstick" type antennas out there, some experimentation
may have to be done with getting the lengths that are usable for this project for good performance.
It would be impossible for us to provide the lengths for all of them within the scope of this article.
A suggestion would be to try your "hamsticks" in a dipole arrangement first, tuned for lowest swr at your desired frequency
and then start the antenna project from there with approximately the same director and reflector lengths. Try 5% longer than driven element for the reflector and 5% shorter than driven for the director. Spacing may not have to be changed.
After it is constructed, lean it up against a very tall non-conductive support away from anything conductive with the reflector on the ground and the director pointing straight up. Add your balun and feedline and start adjusting driven element for lowest swr at your center frequency.
Photograph of the minibeam deployed at the ranch.
It is mounted on a piece of pipe approximately 22 feet high.
I used hamsticks for 20M but any band can be used with the same arrangement.
The following photographs are of the various fittings made to build the minibeam.
This is the fiberglass insulator complete with two metal (aluminum) inserts.
This insulator goes through a hole in the boom and is fastened with a bolt, lock washer and nut. Two small brass bolts are used to make the balun connections. These bolts are inserted through the insulator into the metal inserts. (One on each side)
This is the end view of the insulator used for the driven element.
It is showing the threaded insert and one of the bolts used to connect the balun leads. This insulator passes through a hole in the boom and is fastened to the boom with a bolt, lock washer and nut. The uninsulated inserts for the reflector and the director are mounted through the boom in a similar manner. My boom was reinforced with a sleeve to make it more durable.
This Yagi should be used with a 1:1 balun for best performance and to help eliminate TVI.
One good suggestion is the "Ugly Balun Project" as seen on this site. It works great and is very easy to build from coax and PVC pipe and a few plastic wire ties. It is air woundand nothing special is needed to construct it.
Check it out here on Hamuniverse.com
Many thanks to Russ, VE6VK for allowing us to share his fine project!
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