6 Band Parallel Dipole Array

Three years ago I put up a 15/17 meter dual dipole array, simply a coax going to a 1:1 balun then to the dipoles. The dipoles were separated by 6", were 32' above ground, and flat topped using ropes and pulleys attached to other structures. The SWR was 1.7:1 on both bands and the antenna worked very well.

To maximize the use of space I took the 2 band antenna down and replaced it with a 6 band version which covers 6, 10, 12, 15, 17, and 20 meters. A folded dipole is used for 20 meters, the rest are full size dipoles. The dipoles are made of cheap and light weight 450 ohm window line, 2 antennas per strip of window line, and the antenna lengths are calculated using the formula 468/f mHz 468/18.1 = 25.85' = total length of dipole for 17m. There is a left and right side to a dipole so 25.85/2 = 12.9' so 2 each
13' pieces of ladder line will make the 17/10m dipoles, another 2 each 13' pieces will make the 20/6m dipoles, and 2 more 13' pieces for the 15/12m dipoles. I cut all my dipoles for the lower end of every band. If there are any unused parts of window line with wires longer than 1' cut them smaller so they can't resonate. Other than cutting the window line to your center
frequencies, there are no further adjustments necessary. I call it a PDA, Parallel Dipole Array. A 2 or 4 band PDA might better fit your available space.


I am using a fiberglass push-up mast to support the center of the PDA, and all 6 strips of window line attach to its smallest tube, which is 1/2". Take a piece of window line that will connect to the balun, and using a knife make a slit 1/2' long and 1/2" in and parallel to the window, then open up a 5/8" stainless hose clamp and slip the hose clamp tab into the slit. One hose clamp will clamp both left and right sides of the window line pvc webbing, which is very tough, and there is no stress on the actual wires.

So the very top of my PDA has the 17/10m strip and hose clamp, then 1" space, then 15/12m strip and clamp, 1" space, then 20/6m strip, making my array 5" deep. Below this is the 1 KW 1:1 balun and coax connecter to the radio. This antenna will handle all the power your balun can.

All the left side dipoles ( 6 wires ) connect to the left side of the balun, all the right side dipoles to the right side of the balun.

My window line is 1 " wide so I decided on 1 " spacing for all the elements, and I made hangers/spacers out of steel rebar wire in a figure 8 to attach between the strips of window line. It is 1.25" inside the hanger and I bent them using a jig made with 1/4" sockets screwed to a board then placed in a vice. There is a hanger every 10 windows so the window line cannot twist, and also to maintain the 1" spacing when the antenna is deployed.

The PDA is now up at 32' and flat with no twists so the hangers did their job.

The reason why the PDA works so well is that when you are receiving on a band, say 12m, the strongest signals are received on the RESONANT 12m dipole, its like the other non-resonant dipoles aren't there. When transmitting, the RESONANT dipole with its low resistance hogs 98% of the power applied, the other dipoles have a high resistance of 3000-4000 ohms. So essentially no
matter which of the 6 bands you are on, its like the RESONANT antenna is up there all by itself, the non-resonant ones don't exist.

I expected a SWR nightmare with the PDA and knew it would need a tuner, so it was a pleasant surprise to see that my Yaesu FT1200 internal memory tuner tuned the entire 6m band, all 12m, most of 15m, and all 17m. Because of the harmonic relationship between 20/10m I use an external tuner on those bands, the internal tuner kinda tunes 10m but refuses to do 20m. On 10m the PDA DOES tune on the entire CB band, and the FM part of 10m using the internal tuner. I doubt that any internal tuner will tune 4 1/2 bands on a G5RV, there is something about this parallel dipole array that my tuner really loves.

I called CQ using 50W FT8 digital on 20m the other morning, and a YC1 in Java Indonesia answered and we actually finished the contact, and on 17m I contacted a JS6 on a tiny island in the Philipine Sea with signal reports -4/-5. This antenna will work DX on all 6 bands, it is doing pretty good considering the really crummy band conditions right now 4/8/21. With summer coming 20m
will be open 24/7.

When I first put the PDA up, everything tested fine. The next day 15m wouldn't tune, then that evening it would. I re-soldered the connections and now it works fine. What is interesting was that the other 5 antennas and their tuning DID NOT CHANGE at all during all this. Another thing about the 15m dipole is that my internal tuner will tune it from 19.0 to 21.350 mHz !! Hell of a
range for a touch-up tuner that quits at 3:1 SWR. I need to cut 3/4" off both sides of the 15m dipole some day :O) .

If I had to do this over, I would make the spacing between wires 1/2" by overlapping the window line like shingles and pop riveting them ( or glue, screw, string tie etc. ) so that the pieces of window line make a solid strong structure that will retain its shape and spacing. This type of construction would be perfect for an inverted VEE or sloper etc., only be 2" deep and very strong. I probably should of used stainless steel wire instead of rebar wire...

I have a 10m 3 element Yagi at 40' and a 80-30-12m inverted vee fan at 35', and both antennas have 35+ year old coax. The 12m vee is much noisier than the PDA. My Yagi is pointed at S. America to avoid local noise that the PDA cannot avoid, but the PDA received the same weak signals as the Yagi minus - the Yagi gain. My 20m ground plane vertical is noisier than the
PDA's folded dipole, but the vertical is a real DX magnet. If I cut the 20m dipole out of my PDA, I would bet that the internal tuner would then tune 10m like all the other dipoles, but I ain't cuttin nuttin.

My radio stuff is in the garage, I use TightVNC in the house to look at the computer that does the digital radio stuff, and now when I switch bands while on the PDA, the BEST antenna is always there with the memory tuner, so in theory I can work 4 bands remotely. My radio is on 24/7 and can be found on PSKReporter.info W6TZI. The PDA will be the only antenna used during the day.

Antenna poor to antenna rich in one fell swoop... think about it.

W6TZI