Kurt Andress, K7NV
All Rights Reserved
The available space is the limiting constant for most of us. Deciding what to do with it, is the source of many hours of entertainment.
Here's one way to do it.
Making decisions about where to put the towers in a place of this size is easy, just figure out where you can put the antennas, that the towers will support, where it screws things up the least, while providing the capability you desire. When we put lots of antennas in a confined space, we get lots of interaction between them, that's no surprise. The hard part is in deciding which interactions are the most tolerable for our particular situation and objectives. Before we can do that, a basic goal has to be established. Mine was to have all band capability for a single op, 2 radio station. So, the compromising began.....
I spent many hours modeling antennas with K6STI's AO. I'm no antenna modeling wizard, but I plod along, and am very patient about it and try to make sure that what I'm doing makes some sense, at least to me. If not, I ask someone who knows more about it.
Since, in the short term, I wasn't going to have a tower tall enough to put a 40 meter yagi on, I decided a 4 square would have to do. I had one AB577 and tribander. All the goofing around I had done in the previous two years, with highband antennas for the second radio, convinced me that a second tribander was the best thing to do. The shunt fed AB577 on 80M was pretty good. A second one would be better. Not having a tall anything, to put an antenna on, meant that 160M was a no brainer. Any 160 antenna is better than no antenna. And, anything else I could fit in along the way to add more useful antennas would be good.
I started thinking that the smart thing to do would be to put the low band antennas the furthest distance from the shack for the sake of feedline loss. That meant that the 40M 4 square and the 80M shunt fed tower should be at the southern end of the property. Which meant a decision was required about their placements along the southern property line. It didn't take too long to figure out that having the 40M 4 square shoved into the SE corner was better than having the 80M vert there. This was because, if the 4 square was in the SW corner, looking into the shunt fed tower, while aimed at EU and stateside, its pattern got completely hosed! Having the 80M tower behind the 4 Sq, while it was aimed at those 2 important areas, was far better. And, the locations as shown above were not too bad for the 4 Sq aimed at JA and long path. The 4 Sq was oriented to split the difference between EU and stateside, it's broad lobe allows that, and it was shoved into the SE corner as far as I thought made sense for compromising the radials. Tower #1 was shoved into the SW corner along the same constraints for the 80M radials. That puts it just about in between the JA and LP directions for the 4 square, so its affect on them is minimized.
The next decision was where to put the second AB577 and tribander. The initial preference was to put it somewhere NE of the first tower, so the two towers could be used as a phased pair on 80 at EU/USA and LP. Great idea, until I looked at what the triband beams did to each other when looking at EU and US. It was pretty revolting, one looking right up the tail end of the other! And, having it there also ruined the 4 Square's pattern to the NE. So, I dunced around with it for a while and came to the conclusion that it was far more important to me to have the two triband beams work well when pointed to EU and stateside, than to be able to have a better signal to the NE on 80m. So, the second tower had to go the other way. If I was intent on 80M Dxing, I'd have just put an 80M 4 square out there and been done with it. Unfortunately, I'm not quite there yet.
I played with tower #2's location for a while and discovered that there was a location where it could be placed where both beams would be in the exact same physical relationship to each other, when both were pointed at EU or JA. That meant that I could feed them together with the same phasing line in those two prime directions! The two towers were not too bad either as a phased pair on 80 for JA and SA. So, that's where tower #2 got placed. Putting tower #2 there did affect the 40M 4 square when aimed at JA, but it was not a pattern wrecker! The 4 square is still the best antenna to JA, the old inv vee on the mast over the garage used to be the best one, not anymore, the 4 Square kicks it's tail everytime on weak signals, because its noise rejection is worth far more than any differences in gain, even with the pattern distortions.
This is one of those YMMV things....had to make a decision, so I did.
In 2002 I got the 2 el Cushcraft 40m beam that was up at K5RC's and got trashed by the Dec '01 ice storm. I built a new boom for it, and fixed the elements. This required some more guessing about what to do. I decided to put it on tower #2, to keep it away from the 4 square. But, that meant I had no place to put the second triband beam, which is really important to me. I decided it was better to be louder on 40, than louder on the second tribander. I built a short mast to put the C3 beam on and gave it a try. I'm pretty happy with the results!
With the addition of the 40m beam, I found I no longer needed the 40m inv vee antennas and got rid of them. the low tribander works an amazing amount of stuff. When I have problems, I swap tribanders, which is easy to do with the Six-Pak, and use the TH7. I have a lot more interference between both stations on the tribanders now, but it doesn't freak me out, I'm used to it! The previous antenna placements were better. But, not getting totally pummeled on 40 is a good thing too. It's all just about juggling the compromises.
The experiment continues.......