Since many of the National Parks on the Air (NPOTA) stations have been on 20 meters I decided to build a dedicated vertical antenna for this band. My 80 meter dipole, fed with 450-ohm ladder line, is usable on all bands with my tuner. There were times that the stations I was listening to were near the noise floor and hard to pull out with the dipole.
In my "junk" (aka glorious pile of stuff I haven't figured out what to do with yet) I had an old Hygain CB base station antenna which measured about 21 feet tall. Using the standard 234/frequency I came up with about 16 feet 4 inches for the General section of 20 meters. After adjusting the height of the top section and securing it, I bypassed the CB loading coil in the base by connecting the coax center conductor directly to the vertical element and the coax braid to the mount. The mount is isolated from the vertical element by plastic spacers. I then mounted the antenna to a fence post in the front yard.
After some trial and error I found I had really high SWR. I added a single radial wire to the mount. The SWR came down to about 1.4:1 across the General portion of the band. I had hoped that mounting the antenna to the fence would create a good ground plane but it didn't.
Initial on air test shows it works very well. It tends to hear about one s-unit better than the dipole antenna. As a side note the dipole center is about 20-30 feet above ground with the ends at about 10 feet.
Now that I know the antenna is resonant I plan to put it on a 10 foot mast and add three more radials (for a total of four).
The best part about this project is that the entire building/modification, mounting, and testing took less than an hour! Along with that it didn't cost me anything as I had all of the pieces and parts already. Now to go chase some more NPOTA stations.
