My Hytowers On 160 Meters 

Because I was interested in trying to work DX on 160 meters, getting a hytower tuned would be easy because I had three hytower bases with 65 ft in-line spacing (with radials) installed from previous 80 meter DXing. I was currently using only two phased hytowers on 80 and 40 meters. All I needed to do was load a third hytower for 160 meters at the unused base and go get 'em -which I did. I attained SSB WAS with 100 watts using a single baseloaded hytower. 

But working DX is a different world. A standard 52 ft hytower with a baseloading coil has a very low radiation resistance. Even though I have thirty-two radials in good Texas soil to help lower ground losses, the efficiency is still only about 20%. My goal was to improve my effective radiated power (ERP) to be competitive with local hams using a shunt-fed tower. If you read any literature on loading short verticals, it is apparent that top loading is the best method. But to get a capacity hat on a hytower is impossible because of its tapered whip design. The tapered whip will flex and survive gusty winds without any problems. So to keep wind loading down and remain free standing, I chose centerloading to improve efficiency. 

Construction begin by swapping the first 5 ft X 2 in. OD aluminum tubing section with a 12 ft long tube and inserting the next smaller size of tubing inside for strength. I then swapped the 4 ft X 1.125 in. OD tube with a 6 ft length and inserted the next smaller tube inside it for strength. This brought the total height to 41 ft. I then located a piece of E-glass tubing with 1.125 in. ID and installed it at the end of the new tubing. I attached the remaining tapered whip to the E-glass tubing, which added one more foot and gave me a place to install a centerloading coil. The total length ended up 61 ft. See figure 5. 

When I finished, I still needed a small amount of coil at the base to resonate the antenna, which doesn't have any major impact on its overall efficiency. With EZNEC again, I modeled the 61 ft vertical and overlayed the pattern on the baseloaded pattern. I improved the antenna about 4 dB. See figure 6.

It didn't take me long to decide to phase two modified 160 meter hytowers. I used the same power splitter-combiner I was using on 80/40 meters, since it contains toriod transformers and is broadband. I modified a second hytower exactly as the first and located them on the outside ends with 130 ft spacing endfire east/west. I placed a single hytower for 80/40 meters in the center position. Figure 7 shows the three hytowers in my backyard. 

I ran several models using EZNEC in a phased array. I want to point out, I understand that mutual coupling changes the feedpoint impedance so the driving currents will not be equal. I tried many models using various current ratios and phase delays. The pattern I'm using in this discussion is delayed 90 degrees with 0.4 A on one vertical and 0.6 A on the other. I found that to be a good example. With unequal currents, forward gain doesn't change too much, but the front-to-back (F/B) really goes down (as low as 10 dB F/B). To me that's an acceptable tradeoff for bandwidth and gain.  Figure 8 is a simplified diagram of my power splitter.  Figure 9 shows a comparision between a full-sized vertical over good to my hytowers over medium ground.

On the air operation is very good. In pileups I get through. I've worked every DX station that I've heard -hearing is the real problem. When I switch between east and west my F/B is from 12 to 20 dB, depending on the accuracy the receive station's S-meter.

E-Mail me anytime....

K5QY

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