Quickie Vertical

Hear I am sitting in front of the rig listening to everyone working CQ World Wide, and I don’t really have time for this, but I hear a few interesting stations on 20 meters and try to call them. Trying to bust the pile up with 100 watts and my hustler dipole is going to be difficult on this band, so I tune up on 15 meters and there is action, and I have a good wire beam, so I tune up and down the band and can’t find a clear frequency. Then I hear some one say that 10 meters is open. So I tune up there, and there is a world of DX coming in. I choose a few interesting ones to call, but can’t be heard. I should have expected that, as my antenna for this band leaves much to be desired. It is a vertical above my Hustler dipole, but it has no effective ground plane and SWR no better than 3:1 at its best frequency. With no time to assemble a Quad, I start thinking about a better vertical.

Suppose I take the parts for the quad and make a good ground plane and put the mobile whip above it. That won’t take long. So I quickly assemble a short 4′ mast with a center hub and add four 8′ long 1/2″ diameter fiber glass spreaders and set in on my test stand in the center of the back yard. I dig into my portable antenna box and find an extra mirror mount (Radio Shack variety) and mount it at the top of the mast. Oh, the bolts are too short for the 1″ mast, so I am off to the hardware for 2″ bolts. I remembered that I had cut eight #16 solid copper wires for a ground mounted vertical about a year ago, so I unroll 4 of them and attache them to the lower bolts on the mirror mount and tape the other ends to the tips of the spreaders. I then tighten the wires by dropping the hub 30″ below the mirror mount which pulls the spreaders into the horizontal position and allows the radials to drop at about 17 degrees. Quickly, I mount the Hustler 10-meter whip, connect the coax, and check the SWR. The SWR is great, 1.1:1, but at 29.6 MHz. So I add two more inches to the stinger and recheck. That gave 28.6 MHz for best SWR which is now 1.2:1. Not bad, a total of a half hour has passed, and the same stations are still holding the frequencies. So I start down the list that didn’t answer earlier. To my amazement I work each one within a minute. So there I sat wishing I had time to work the contest.

To complete the story, the radials are 101″ inches long. The spreaders were at an elevation of 4 feet above the ground. Later, I raised this to a height of 8 feet, and nothing much changed. I also tried resonators for 12, 15, 17, 20, 30, 40 and 75 meters with equally good impedance matches, but I didn’t raise them up. The table below gives the measured SWR and bandwidth for each band. A photo of this antenna is shown below the table. As I really didn’t design this antenna, we have to call this one just plane luck. By the way, if you want more radials, it is possible to use two hubs with one rotated 45 degrees to the other. Add four more spreaders to get 8 radials. This might reduce the stinger lengths a little, as mine are fully extended on a few of the bands. The 20 meter Ham Stick wasn’t long enough to get down into the CW portion of the band, so I added four alligator clips to the tip of the stinger. This worked about the same as the Hustler, So here is an antenna that can be set up in as little as 15 minutes once you have the parts together. If you paint all the parts black, it is nearly invisible at night and not objectionable by day. Note that this antenna works fairly well on 75 meters, but does not work well on 30 and 40 meters. I’ll tell you why some time later after I figure it out.

 

Note, the bandwidth is the SWR bandwidth for 2.0:1, and the stinger length is measured from the top of the compression nut. All configurations use the Hustler MO-3 mast part, and all resonators are the low power versions. It is interesting to note the excellent match on 75 meters. Normally, this whip gives a much lower impedance when set on a good ground plane, so this probably means that at least half of the power is going into the ground, even more is lost in the loading coil, but it still works pretty well.

 

 

Article by  KQ6RH originally available at http://w2so.org/projects/antennas/quickie-vertical