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20 Meter "Vertical Zepp Dipole" Antenna
Carl H. Dahlberg  N7AGK 

Editors note:
The author of this project arrived at these plans by experimentation so this antenna
 should be considered an experimental project by the builder
It was designed for the 20 meter band and works well on DX!

 I tried an antenna that you may be interested in.  It tunes up very well with my rig using an antenna tuner.  It does not need radials like a 1/4 wave vertical antenna does. 
The antenna is a 2" diameter aluminum tubing about 16'8" long.  It is about a 1/4 wave long at 14mhz.  (It may be a little bit long but I have not cut it off.)   A coax cable is run up through the center of the tubing and the center wire is connected to the top of the tubing.  The shield is left open and is not connected to anything at the top.
 I have fitted a PVC pipe to the bottom end of the aluminum tubing and brought the center wire and shield out to 1/4 " bolts.  The coax cable from the antenna tuner is connected to the bolts.  The PVC pipe at the bottom of the antenna fits into a steel pipe which is mounted on a wheel and tire of a car which is the base mount for the antenna.  Presently I have the antenna mounted on top of my garage but it can also be mounted on the ground as long as it is insulated from the ground. The wheel and tire "support" works well. Use your imagination for the support.

One big advantage of the antenna is that it does not need radials. 
Although I am not positive about the actual "description" of this antenna here is my best opinion of it's description.
The tubing is one half of a dipole.  It looks like a vertical 1/4 wave antenna but is actually a zepp dipole according to my limited research and could be related to a Bazooka type antenna.....just not sure.....but the short story is that it works fine.

How to put it all together!
Don't get confused as to the wiring and construction of the antenna.
It is rather simple. See the drawing below.

The coaxial cable is fed down or up, your choice, through the tubing and is connected to two bolts at the bottom on the PVC section.  One connection is for the coax center conductor and the other is for the coax shield.  The center conductor of the antenna coax is connected to the coaxial cable center conductor that goes to the antenna tuner.  The shield is connected  to the coaxial cable shield. Now that was simple! Are you done yet?

Drawing above is a suggested method of using a car wheel and tire as a support base..use your own imagination for the base support. The overall height of the antenna plus support will be about 17 feet plus or minus the width of the tire. The tire not only acts as a heavy base support but also as an additional insulator from the ground. If you leave it up permanently, you may want to guy it in three directions with rope, cord, etc if you are subject to winds. Non-conductive of course. Also, you may want to seal the coax end and the connections on the PVC from Mother Nature.

Some preliminary results of on the air testing!
Yesterday afternoon I was listening on 20m and heard a Japanese station, (JA1YPH), who was working a contest on CW.

I answered him and he gave a RST of 599.  I heard him 599 also. I heard 4 other Japanese stations but did not answer because they were in a contest.  They ranged from RST 579 to 599. 

A comparison of antennas.
I have
a 20m dipole on my tower which is 45 feet up and the signal with the 20m Zepp Dipole is usually better and sometimes the same as the antenna on the tower which is very encouraging. I had tried the 20m Zepp Dipole previously and did not get satisfactory results.  I noticed later that the shield on the coaxial cable to the antenna was not making good contact.  I corrected it. When I tune
now with the antenna tuner I can tune to zero SWR.

Experimentation on other bands:
I tried tuning the antenna on 18mhz and it tuned fine.  Tried it at 21mhz and it would not tune correctly.  Also tried it at 7mhz and it would not tune there either. So with these preliminary on the air results, we now have a "dual bander" 1/4 wave vertical without radials using a tuner! All this for some time, effort and some  experimenting fun!.......I wonder what is next?

Additional notes:
You may want to experiment with other bands and tubing sizes...larger tubing sizes should yield more bandwidth. Try the standard 1/4 wave formula:
234 / freqmhz = total length in feet, as a start for the tubing length......
Let us know how they work for you! Please email us with your results!

N4UJW at hamuniverse.com (Sorry no current email address for N7AGK)

Updates from other builders:

Subject: 20 meter antenna project
To: n4ujw@hamuniverse.com
Date: Wednesday, March 24, 2010, 8:24 AM

Just wanted to let you know about the success I have had with an antenna project from your web site; 20 Meter "Vertical Zepp Dipole" Antenna by Carl H. Dahlberg  N7AGK. 
I built it using 3/4 inch copper pipe with rg-8 running up the center.  I'm operating a FT-897D at 100 watts thru a MFJ tuner on 20 and 17 meters.  The antenna tunes well on both bands and I have worked many stations in North & South America and Europe.  Nothing heard from Asia or the Pacific... yet.  Total cost from Home Depot was $28 (2010 prices). 
No ground, no radials, WOW.  Thanks!
John Paul St. Peter, KD8JSP (email address at QRZ.COM lookup)



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