Simple Ham Radio Antennas: The Aluminum Foil Vertical. Post #278.


I knew it would happen.  The time I ran out of antenna wire.  After several years of using old #14 AWG house wire, #18 AWG speaker wire from Radio Shack, and remnants from studio wiring projects at my former employer (Pacific Radio Group), I had finally exhausted my wire supply for homebrewed antennas.  What to do until the next sale at Lowe’s, Home Depot, and Ace Hardware?  Give up? Banish the thought!.

With last week’s beautiful weekend before me, I needed some cheap wire to erect my latest antenna “masterpiece.”  I found my resource in the kitchen in the form of a new roll of “Diamond Aluminum Foil”–the stuff my xyl uses for cooking tasty treats and dinners.  Since there were several new rolls near the stove, I decided to “borrow” a new roll and apologize later.  Besides, I would buy another roll the next time I visited the supermarket.

According to the label on the container, the roll contained 66.66 yards (199.98 feet) or 60.96 meters of aluminum foil.  The foil measured 12 inches/30.48 cm wide.  By carefully cutting a narrow strip of aluminum foil and taping it to a MFJ telescoping fiberglass mast, I would have the crude beginnings of a 40-10 meter vertical. By attaching carefully cut lengths of aluminum foil to my feed line, I could also make a crude, but satisfactory “counterpoise” system to complement the vertical element.  By using a few aluminum nuts and bolts, I could attach a 450 ohm ladder line to the foil elements and have a multi-band antenna capable of working 40 through 10 meters.  A sturdy antenna transmatch (“tuner”) and a 4:1 current balun would permit operation with my Ten-Tec Argosy II transceiver.

If the antenna “fizzled”, all I would lose is some aluminum foil and a tarnished ego.  So, with aluminum foil, some basic tools, a spare mast and assorted tape and nylon ties, I ventured forth into the abyss.

MATERIALS:

Here are the materials I had available in the shack and in the garage:

One 33-ft/10.06 meters MFJ telescoping fiberglass mast.

A spare 5-ft/1.52 meters wooden support stake for the mast.

Two, 5-ft/1.52 meters wooden stakes to support the 450 ohm feed line until it reaced the garage wall, where I had positioned a W9INN 4:1 current balun approximately 8-ft/2.43 meters above ground.

Fifty feet/15.24 meters of 450 ohm ladder line.  This would be the antenna feed line.

Six feet/1.82 meters of RG-8X coaxial cable with UHF fittings. This cable would run from the balun to the window patch panel.

Six feet/1.82 meters of RG-8X coaxial cable with UHF fittings. This cable would run from the patch panel to the Drake MN-4 transmatch (“tuner”).

Short pieces of RG-8X coaxial cable (3-ft/0.91 meters) to interconnect the Argosy II, low-pass filter, and Heathkit Dummy load to the Drake MN-4.

A “counterpoise bundle” consisting of 1/4 wavelength wire pieces for 40, 20, 15, and 10 meters.  For the counterpoise, I used a wire bundle from a previous antenna project.  The counterpoise bundle would be connected to the ground lug of the Drake MN-4.

And finally, a set of nuts and bolts to attach the aluminium foil vertical element and counterpoise wire to the 450 ohm feed line.

ASSEMBLY:

The antenna was built on the ground.  To determine the length of the vertical element, I used the general formula 234/f (MHz)=L (ft.)  Using 7.088 MHz as my selected frequency (the local “watering hole” for the Hawaii Afternoon Net), I carefully cut an aluminum foil strip 33-ft/10.06 meters long and 0.5-in/1.27 cm wide.  I cut two “counterpoise” wires having the same length and width.

I secured the thin aluminum foil vertical element to the fiberglass mast with nylon ties and vinyl electrical tape.  At the bottom of the vertical element and at the ends of the aluminum foil counterpoise wires nearest the mast, I carefully secured each leg of the 450 ohm ladder line with aluminum nuts and bolts.  One leg went to the vertical element.  One leg went to the junction of the two aluminum foil “counterpoise wires.  I wrapped the base of the fiberglass mast with plastic bags to protect the antenna and counterpoise connections from the weather.

I slowly hoisted the mast onto its wooden support stake and attached the 450 ohm feed line to two wooden support stakes to keep the ladder line off the ground.

The aluminum foil counterpoise lines were carefully supported by low level wooden garden stakes.  The counterpoise elements were approximately 6-in/15.24 cm above ground.

The 450 ohm ladder line was attached to the W9INN balun on the garage wall, a 6-ft/1.82 meters length of RG-8X with UHF connectors was attached to the balun, the coax was led to the window patch panel, and a final 6-ft/1.82 meters length of RG-8X was run from the patch panel to the Drake MN-4.  Smaller pieces of RG-8X connected the transmatch to the Argosy II, the low-pass filter, and the Heathkit Dummy load.  As a final step, I attached a “counterpoise bundle” to the ground lug of the Drake MN-4.

INITIAL RESULTS:

For a rapidly made, spur-of-the-moment antenna, results were surprisingly good.  With the Drake MN-4 in the line, I was able to get a SWR of 1.1 to 1 on 40, 20, 15, and 10 meters.  With the Argosy II running around 10 watts, I was able to get some excellent contacts both in Hawaii (late afternoon) and the U.S. mainland (late morning through early evening hours).  On average, depending on the band in use, CW reports ranged from 559 to 599 and SSB reports fell between 54 to 57.  Not exceptional, to be sure.  But the antenna works.  Best of all, my cost was virtually nil, except for the aluminum foil which my xyl will soon discover is missing.

I’ll keep the antenna up for a few weeks, just to see how well it survives our summer showers and tropical heat.

This was a fun and educational project.

REFERENCES:

http://www.arrl.org/hf-vertical.

http://www.dxzone.com/catalog/Antennas/Vertical/.

http://astromag.co.uk/vertical.

http://www.wc7l.com/VerticalTheoryp1.htm.

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Aloha es 73 de Russ (KH6JRM).

BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

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