Monday, February 17, 2014

Simple Ham Radio Antennas: The W3EDP antenna revisited. Post #261

The "classic" W3EDP antenna has been around since March 1936 when Yardley Beers (W3AWH/W0JF) described a multiband antenna built by his friend H.G. Siegel (W3EDP).  Siegel used the traditional method of "cut and try" to arrive at an antenna length that would work satisfactorily on 160, 80, 40, 20, and 10 meters.

Beers remembered that "A length of 84 feet (25.60 meters) seemed to stand out as being the best of all the combinations tried."  A similar "test and tune" method was used to determine a satisfactory counterpoise length of 17 feet (5.18 meters), "as the one working best in combination with the antenna."

Since that time, several variations of this true "Zepp" antenna have been developed to facilitate portable, emergency, and even home use.  Many QRP enthusiasts use some kind of W3EDP-derived antenna for their operations.  The W3EDP antenna is a simple, cheap, and field deployable.  The antenna requires a 1:1 or 4:1 current balun and an antenna transmatch to work properly.

Several months ago, I built a replica of Siegel's design at my new homestead in the Puna District of Hawaii Island.  I configured the antenna as an inverted "L", using a 33-foot/10.06 meters MFJ telescoping fiberglass mast as the main support.  One wire ran up the mast, with the remaining 51 feet/15.54 meters of wire run horizontally to a nearby Norfolk Pine Tree.  A W9INN 4:1 balun was secured inside a waterproof plastic storage container at the base of the mast, with 17 feet/5.18 meters of AWG #14 house wire  attached to one terminal of the balun and 84 feet/25.60 meters of AWG #14 house wire attached to the other balun terminal and run up the mast and then onto the tree.  The "counterpoise" wire was elevated 3 feet/0.91 meters off the ground to a nearby wooden stake.  Twenty- five 7.62 meters of RG-8X coax was attached to the balun, run into the shack, and attached to my trusty Drake MN-4 transmatch. 

That arrangement worked well and was largely invisible to the neighbors.  I later took down the antenna and stored it in the garage.

Not much else was done in this area until I discussed the W3EDP antenna with Dean Manley (KH6B) at one of our impromptu meetings at the Hilo Jack In The Box Restaurants on Thursday, 13 February 2014.  He gave me some reference material on Siegel's antenna, which I found most valuable, since I was considering re-erecting another W3EDP antenna on my property.

This time around, I decided to incorporate 17 feet/5.18 meters of 450 ohm ladder line as part of the system.  This vertical variant of the W3EDP antenna was used successfully by AE5VV , NC4FB, and other hams.  The antenna would have a vertical section of 450 ohm ladder line, with one leg of the ladder line attached to 67- feet/20.42 meters  of AWG #14 house wire run up a fiberglass mast and then onto a nearby tree--the very same support system used in my first W3EDP antenna.  The left leg of the ladder line would be left as is and would serve as a matching section for the antenna.

The 4:1 balun would be in the same plastic storage box as before, but with a "counterpoise" bundle consisting of a 17-ft/5.18 meters length of #14 gauge wire and the another #14 gauge wire measuring 33- feet/10.06 meters.  The longer wire would be used for 80 and 40 meters, while the shorter wire would be used for 20 through 10 meters.  Some amateurs who have built this antenna say the shorter wire isn't necessary for 10 meters.  I just left the wire in the system.  The "counterpoise" system would be connected by small battery clips, depending on the bands chosen.  I also attached the same "counterpoise" bundle to the ground lug of my Drake MN-4 antenna transmatch.

Finally, 25-feet/7.62 meters of RG-8X coaxial cable would be attached to the balun and run into the shack's Drake MN-4 antenna transmatch.

MATERIALS:

Most of the materials left over from the previous W3EDP antenna were reused.

I secured 17-feet/5.18 meters of 450 ohm ladder line to the fiberglass mast.  The "counterpoise" bundle was attached and soldered to one leg of the ladder line, while 67-feet/20.47 meters of antenna wire (#14 gauge house wire) was attached and soldered to the remaining leg of the ladder line.  All connections were covered by several layers of vinyl electrical tape.  The vertical wire was secured to the mast by nylon ties, with the remaining length (51-feet/15.54 meters) of wire  shot over a branch in a nearby Norfolk Pine Tree with a slingshot.  The branch was about 30-feet/9.14 meters above ground.  The end of the antenna wire was attached to a ceramic insulator and tied off with some fishing line I had in the garage.  The total length of the vertical element measured 84-feet/25.60 meters.

I hoisted the mast onto its wooden support stake and attached the "counterpoise" bundle to a nearby wooden stake.  The stake kept the wires approximately 3-feet/0.91 meters off the ground.  I then attached 25-feet/7.62 meters of RG-8X coaxial cable to the balun, ran the cable through the shack's patch panel, and attached the cable end to the Drake MN-4 antenna transmatch.  Small pieces of coax interconnected the antenna "tuner" to the Ten Tec Argosy II, a low pass filter, and the Heathkit Dummy Load.

INITIAL RESULTS:

Not bad for a quickly built antenna.  With the help of the Drake MN-4, I can get SWR readings of 1.3 to 1 across my bands of interest.  Even with the Argosy II running 5 watts, I get plenty of contacts  in Hawaii, throughout the Pacific, and on the U.S. mainland.  Most of my cw signal reports are between 559 and 579 with ssb contacts ranging from 54 to 58, depending on the band in use.  I had a lot of fun building this "classic" antenna.  It works.  It's cheap. And it's lightweight.

REFERENCES:

Manley, Dean W. (KH6B).  "If it's not 84 feet, it's not W3EDP."  Contained in "On Frequency", Volume 41, No. 6.  June 1998.

Beers, Yardley (W3AWH/W0JF).  "An Unorthodox Antenna."  "QST", March 1936. pp. 32-33.

W3EDP Antenna.  "World Radio".  November 1997.  p. 59

The ageless W3EDP antenna.  "Technical Topics."  April 1985.

http://www.ok1rr.com/index.php/antennas/19-the-w3edp-antenna.

http://www.nc4fb.org/wordpress/w3edp-multi-band-antenna.

http://www.zerobeat.net/g3ycc/w3edp.htm.

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Aloha de Russ (KH6JRM)

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