A VERTICAL ANTENNA FOR 15-METERS
Now that the New Year is here, why not start the year right by building a simple vertical antenna for 15-meters? The materials are inexpensive and can be found at the nearest hardware or home improvement store. If you’re a rf “packrat” like me, most of the antenna is probably stored in your “junk” box.
The 15- and 10-meter bands are some of my favorite hangouts. When propagation is favorable, dx from my dry spot in the Central Pacific can be exciting. My qth is located along the Hamakua Coast of Hawaii Island, just about 2,100 miles south west of Los Angeles. There’s nothing but ocean between my shack and the bright lights of Hollywood and the entire West Coast of the mainland U.S. Propagation to the northwest and most of northern Asia is a bit hampered by the presence of 13,000-foot Mauna Kea, but not terribly so. I get plenty of contacts from Japan, Korea, and Asiatic Russia with the simple vertical described below.
A 100-foot spool of antenna wire. Although I prefer #14 AWG household wire or a similar gauge of Copperweld wire, all I had on hand yesterday (Saturday) were several spools of #20 AWG hookup wire. Since the antenna was going to be only a temporary arrangement, I could get by with what I had in the storage room.
50-feet of coaxial cable. You can use either 50-ohm coax (RG-58, RG-8, RG-8X) or 75-ohm coax (such as RG-6). I happened to have some RG-6 from an old studio installation at my former employer (Pacific Radio Group–Hawaii Island). Earlier, I used two “F” to “UHF” adapters to make the cable usable for my station. The trusty Drake tuner (MN-4) would take care of the small mismatch present in the antenna system.
A Budwig center coax connector. The + side would be connected to the vertical element, while the – side would be connected to the elevated radials (4).
A mast of suitable height. I used a spare MFJ fiberglass mast for the antenna support. My mast was 33′ tall (approximately 10.01 meters).
A tuner to manage the small mismatch present in the system.
Four insulators and four posts to tie off the elevated radials.
An antenna grounding system to bleed off static electricity and provide some protection from lightning. Integrated ground and static discharge systems for antennas can be found in the 2012 Fall/Winter AES catalog.
A sturdy post to mount the fiberglass or pvc mast.
Dacron rope to tie off the elevated radials. The elevated radials can be used to guy the antenna.
I assembled the antenna on the ground. I measured out and cut the vertical element to a length of 11′ 1″ (3.38 meters). I measured out and cut the radial elements to a length of 11′ 4″ (3.45 meters). According to Ed Noll, W3FQJ, these lengths would make the antenna resonant at 21.150 MHz.
I attached the vertical element and the radials to the Budwig center connector. Each connection was soldered, coated with clear fingernail polish, and sealed with vinyl electrical tape.
Dacron rope was fastened to each end insulator of the elevated radials. The tie offs would be made after I lifted the antenna onto its support stake.
The vertical element was fastened to the fiberglass mast with nylon ties. The bottom of the vertical element was attached to the mast at mid-point, approximately 16′ or around 5 meters above ground level.
I attached the feed line to the UHF connector on the Budwig center coax connector.
I raised the mast and positioned it on a support stake.
I tied off the four elevated radials to prepositioned ground stakes.
I attached the coax to the static discharge/ground system below the window of the shack and connected the discharge unit to my antenna tuner with a small length of RG-6 coax.
SOME PRELIMINARY RESULTS
Although I’ve had the 15-meter vertical up and running for only two days, results have been encouraging. Fifteen meters is quite active between 1100-1600 hours local time (2100-0200 UTC). Most of my contacts have been with the continental U.S. with CW reports ranging from 559 to 579 and SSB reports holding between 54 and 56. Not too bad for 10 watts. I’ll leave this “skyhook” up for a few weeks to see if propagation improves.
Total cost for this project: $0.00. I had all of the materials in the storage room, so a trip to my local hardware store in Hilo (30 miles) wasn’t necessary. Besides, the weather was sunny and I enjoyed the time outdoors. Listed below are some references that may prove useful in your next “homebrew” vertical antenna effort.
Edward M. Noll, W3FQJ. Easy-Up Antennas for Radio Listeners and Hams. Limited Edition, 1991. MFJ Enterprises, Inc. p. 110.
“How to Build an Antenna”. http://www.ehow.com/how_4617340_build-antenna.htm.
W5ALT. Indoor Vertical Antenna. http://www.comporto.com/~w5alt/antennas/index.php?pg=3.
Have a safe and prosperous New Year!
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Until next time,
Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.
Filed under: Amateur Radio