55' Vertical Antenna For 40/80/160 Meters
The basic antenna is a vertical monopole, using elevated radials to complete the "ground plane." I use it only on the weekends, primarily for contests, thus it is designed to be raised and lowered with a minimum of fuss. It is a full-size 40 meter 1/4 wavelength vertical, with from four to eight tuned radials run parallel (horizontally) to the ground at 10' elevation. It's performance has been excellent for me, much better than any ground-mounted vertical I have used and is often as much as 12 dB (2 or 3 S-units) stronger than my trapped inv-vee with the apex at 35'.
At the top of the 40 meter section (34' of aluminum tubing) is a lightweight coaxial trap made up of RG-174U on a 2" OD PVC form.Look at picture of 40 m and 80 m traps
Above the 40 meter trap is another 12' of aluminum tubing; the last 6' is 3/16" aluminum rod with a small top hat made of #12 gauge copper wire. This top section resonates on 75 m and gives me almost 200 kHz between 2:1 SWR points.
For 160 meters, I have tried various configurations, including the trap shown in the picture above with a pair of "top hat" wires angling down at 45 degrees, an inverted-L configuration using just the 34' of aluminum (1999 CQ 160), and a base-loaded coil made from #10 gauge wire. For the 1999 ARRL DX Phone contest, I just configured the antenna without the 160 meter sections and loaded the 40/80 meter antenna using my rig's tuner. This worked acceptably, as I could work every station I could hear, and was a much easier installation.
The elevated radials shown in the picture at the right are made from #14 gauge insulated wire and have coaxial traps made for 40 meters and 80 meters. Rough dimensions for the wire are shown in the sketch above. The radials are resonant at 10' off the ground for 40, 80, and 160 meters. The 40 m and 80 m traps are made using some scrap RG-8X on 2" and 2-1/2" PVC pipe forms. Note the large U-bolts used to secure the lowest section of the antenna through the elevated base "tee" section. Also visible in the picture is my 8' step ladder, an air-wound coax RF choke in the feedline, and a couple of the guy wires.
The elevated base is constructed of two 2x4's arranged in a "tee" configuration; one is 10' long and the other is 12' long. A matching 3' section is set in the ground (with 2 bags of concrete) for connection via a barn door hinge. See the picture at left for the erected position (top) and the storage position (bottom). The 2x4 lumber was treated with wood preservative and several coats of exterior latex paint. The entire 12' base plus the 45' of aluminum can be safely "walked" up by one person and then guyed. Typically, this is an "up at dusk, down at dawn" operation for me on contest weekends.
Article and Copyright by K5OE originally available at