Five Bands, One Feedline
Since I started this website and posted this particular page was under construction, I have moved once and changed the configuration of this antenna multiple times. The first attempt at this antenna had four dipoles connected to a 1:1 200 watt Jetstream balun.
The 80 meter radiator was made from 1/16 inch steel wire rope so it would support the weight of the other elements. The rest were 14 gauge SIS wire, cut for the 40, 20, and 10 meter bands. I expected this to give me five bands (thinking I would get 15 meters from the 40 meter dipole) and I was happy getting a reasonable match on all of the dipoles (<1.5:1 on my antenna analyzer) figuring the antenna tuner in my radio could match the rest of the way, and for the most part, it did. As an unexpected bonus, I also got 6 meters <2:1. I am not sure how, it must be an odd harmonic of one of the imperfect dipoles.
I was able to get 15 meters, but it was nowhere near resonant and I burned up a lot of my transmit power in the tuner. But the 80 meter element just was not good. No matter what I did, my radio did not like the 80 meter dipole. The antenna analyzer showed it somewhere in the middle of the SSB segment of the band (I do not remember where exactly, but I know I have it written down (but I do not remember where)) but when I loaded it up with the radio it just would not stay tuned.
I checked everything I could think of, and finally gave up and removed the 80 meter wire and replaced with copper stranded, cut for 40 meters. I then recut all of the other wires down to the next band I wanted: 40 became 20, 20 became 15, 10 remained the same. I spent some extra time tuning and they were resonant in the middle of the SSB portion of their respective bands with the exception of 10 meters, I tuned it for the center of the Technician section of the band, expecting most of the activity there. I ended up with the same bonus of 6 meters, and it also tuned part of the 2 meter band! The last configuration may have also tuned 2 meters but I never tested for it.
This four dipole fan is my current configuration, and I am pretty happy with the performance, but it is not perfect. For one thing, like all dipoles, it receives better than it radiates (it is non-directional), it does not have 80 meters, and it it is kind of ugly. Reworking the antenna is always on my to-do list. I just kept putting it off. And thenů
I purchased a 600 watt amplifier, so this spring, the antenna will get an upgrade and a much needed makeover. Due to my lot size and configuration I am going to attempt to add an 80 meter shorty to the antenna (and replace all of the insulator/ separators) as well as upgrade the balun to a higher power model so I can use the new amplifier.
The center of the antenna will be 30 feet off the ground with the elements as flat as I can get them, between 15 feet and 20 feet. I am going to use an MFJ-918 or Jetstream JTBAL11G current balun and feed the antenna with RG-8 coax with the feedline being around 40 feet in length.
The configuration I am attempting is dimensioned below. I am using the standard 468/f formula with no adjustments for angles and I am just going to cut them long and trim them as needed using my antenna tuner. Wire will be #14AWG Stranded SIS or THHN and insulators will be 3/8 inch PEX tubing.
|Band||Center Freq||Total Length (1/2 wave)||Single radiator (1/4 wave)|
|80m Shorty||3.800||85 feet||42.5 feet (includes loading coil)|
|40M Dipole||7.2125||64.89 feet||32.45 feet|
|20M Dipole||14.250||32.85 feet||16.43 feet|
|15M Dipole||21.325||21.95 feet||10.98 feet|
|10M Dipole||28.400||16.48 feet||8.24 feet|
Spacer 1 & 2: 26 inches, holes drilled at 2 inches, 7 inches, 12 inches, 17inches, & 22 inches
Spacer 3: 21 inches, holes drilled at 2 inches, 7 inches, 12 inches, & 17 inches
Spacer 4: 16 inches, holes drilled at 2 inches, 7 inches & 12 inches
Spacer 5: 11 inches, holes drilled at 2 inches & 7inches
The distances between spacers is listed below:>
I will post pictures of the build once it is completed.