
Introduction:
If Ā you look at this site, you will see that I have beenĀ fightingĀ anĀ RFI problem for years… Ā For the most part I have it beaten down, and it seems to not be coming back… Ā So… Ā That said, I decided to construct a four square array for 40 meters, and a two element 30 Meter phased array, so I could null the remaining RFI, and gain some signal too boot. Ā This also gives me a decent 30 meter Antenna array as well… Ā A four square system is not a small project, you need four verticals, miles of ground wire, a phasing unit, and some land, couple that with a two element 30 Meter phased array and you end up needing something like two miles of ground wire, and five antenna… Ā For the past few decades I have been threatening a 40 Meter phased array, maybe two elements, maybe parasitic, or maybe driven, I never reallyĀ committed.
I had a failed tower project, and found myself with a slight surplus of money after I sold everything dealing withĀ theĀ tower… Ā The cash I wasĀ goingĀ to use for the tower, could be redirected to the fourĀ square project. Ā So I decided to build a phased array for forty and 30 Meters! Ā As I see it the pros/cons as as follows:
Pros:
- I can null out the RFI.
- I get gain.
- I get the fun of tuning and installing it.
- Helps out on DX.
- FinallyĀ finishĀ my decades long promise to build a phased array for 40.
- I have always wanted a good 40 meter beam…
Cons:
- Cost is high, probably around $1000 for everything.
- Requires lots of land.
- Tune up is tough.
- Attention to detail is paramount…
- RequiresĀ MILES of wire for ground screen.
Getting started:
The first thing I did was toĀ inventoryĀ the site to insure I had room for the array, and the ground system, which isĀ significantĀ Ā I wanted to be sure I had the space for a four square… Ā IĀ brieflyĀ thought about one for 75 Meters, then decided the lot was not large enough… Ā As you can see from the photo, the lot is long and skinny… Ā It is 60 feet wide, and 300 feet long, a bit slim for a full four square on 40, so I will use compromised radials. Ā The lot would better lend itself to a linear array, but I want a 4 square so I can point the null at my RFI sources, of which I have a few. Ā If I used a linear array, I would have very limited control of the null. Ā Thus the decision on a four square.
The first thing was to get a scaled drawing of the lot and the array with Ground radials… Ā That told me instantly that a Four Square on 40 Meters was out of the question for my lot… Ā Click any photo for a larger view.

As you can see, even though it would fit, the compromises would be too much for 40 Meters… Ā The radials in the North/South direction would be compromised, to say nothing about being up againset a chain link fence on the south side, and an eight foot metal fence my neighbor to the North put up… Ā So… Ā Change of plans!

30 Meters for the Four Square array, and 40 meters for the two element array. Ā As you can see from the photo, things fit a lot better, and I have room for my 40 Meter two element array, which I will construct first. Ā Doing the layout early on let me know where to place the 40 Meter verticals, and where the 30 Meter verticals go as well.
I am considering the Comtek 40VA 40 Meter vertical antenna, from DX Engineering, Ā for the elements of the two element 40 Meter array. Ā I have purchased one, and the construction is superb. Ā However I will more than likely go with a Gap Challenger DX for the 40 meter elements as I have two of them now. Ā This got me to thinking about the radial field… Ā If I can correctly phase the two Gaps, then I can avoid the massive radial field needed. Ā If this is true, then I will buy Mono Band Gap Verticals for the 30 meter array.

I decided to construct the array one antenna at a time, making that antenna asĀ perfectĀ as possible, then moving on to the second element. Ā I also decided to set it up as a fixed direction initially for testing. Ā The idea would be to take careful readings prior to addingĀ theĀ second element, then add it and retake the S Meter readings over time. Ā That way I could get a rough idea if the beam was working, and whatĀ theĀ F/B ratio would be. Ā This would help me with the RFI issues, and it would help in reduction of QRN in general… Ā Overall a three db increase in signal won’t harm things either… Ā I am looking forward to testing this array. Ā I have arranged to test with several hams inĀ theĀ area, some in the near field, and some several miles away. Ā I want to get a true reading on the F/B, F/s ratios in both near and far fields.

The first thing thatĀ happenedĀ was I hit a tree root… Ā Three days later, I was still working on that same root. Ā I decided to bring in a professional equipment for the job. Ā I called a Fence contractor, they dig lots of holes for a living, and they put poles in them as well… Ā Sounds good! Ā After I got a bid for the job of installing seven posts I decided to do a lot of it myself… Ā They fence contractor charged me $20.00 bucks per hole. Ā That includedĀ back-fillingĀ with Sand/Gravel. Ā As I was tired of using the post hole digger above, I elected to have them drill the holes for all posts needed…
In comes the heavy equipment… Ā ThisĀ took no time in digging all seven holes… Ā In fact, it took under an hour to do all the holes, the fellow running this device was a pro. Ā He would drill a hole, then use aĀ post holeĀ digger to clean it up. Ā One of the funny things I noticed… Ā Every tool with a handle had the handleĀ removedĀ and replaced with a galvanized fence pole… Ā The owner must have broken a few of the handles at one time…
As can be seen, this is one of the holes for the front right 30 meter antenna, as viewed fromĀ theĀ house looking East. Ā We finished the holes on a Friday morning, and I decided that it was time to do theĀ concreteĀ work… Ā I took out my calculator and did the math for how much concrete I would need… It worked out to .9 bags per hole! Ā Great, Seven holes, seven bags… Ā I ordered the concrete, and a Mixer. Ā The Mixer costĀ somethingĀ like 20 bucks a day… Ā Well worth not doing a hand mix in aĀ wheel-barrel. Ā I also wanted the mix to be decent, not something I was moving around with aĀ shovel. Ā The mixer, and concrete arrived andĀ theĀ fun began. Ā Myself and one other ham, and one friend began work on this… Ā One thing… Ā If you mix concrete, follow the instructions, no matter what you think, no matter what anyone tells you. Ā The concrete maker knows what it takes to get a good mix… Ā All three of us looked at the instructions and said, WTF? Ā One gallon of water for 90 pounds of mix? Ā You have to be kidding! Ā We followed the instructions, expecting things to go bad… Ā They did not, the concrete looked perfect, every time… Ā We mixed one bag with one gallon of water, and pored after five minutes of mixing. Ā Every pour was perfect. Ā The amount was right, and the mix was right… Ā I mounded each pour up on the pole to drain off water fromĀ theĀ pole.

After four hours we were finished… Ā All in all the creation of the infrastructure was not thatĀ difficult. Ā it took seven bags exactly of concrete to finish this part of the project. Ā Each pole has a raised mound of concrete at the ground/pole interface to keep water from pooling on the pole. Ā Each pole is 1/4 inch galvanized pipe, and each pole will have a cap on top to keep rain from entering the pipe. Ā What rain/condensate does get in, will drain outĀ theĀ bottom into the sand/gravel. Ā ThisĀ will also serve to keep the cut end of the pipe out of a water pool underground. Ā The top caps have not been placed yet, as the concrete is stillĀ fragile. Ā I will wait a few more days to place them. Ā Once in place, they should protect the poles from filling with water when it rains. Ā In Oregon it rains most of the winter… Ā By that, I mean it actually rains 90% of the time. Ā While we don’t get huge amounts of rain, we get a stedy drizzle for months at a time. Ā Ā This tends to fill things like poles up fast. Ā So… Ā The idea of a fence cap. Ā It also makes the array look a bit more professional as well… Ā The detail of the hole itself is presented here on the left. Ā Sorry for the quality of the drawing, I did not major in engineering drawings…

Here is the final photo prior to a bit of trenching. if you look at the photo carefully, you can still see the post levels on three of the posts. Ā I will next trench for the feedlines, and control cables. Ā I probably should place them on top of the radial field so I can get to them, but I have decided to put them low, as opposed to high. Ā My thinking is that havingĀ theĀ control cablesĀ beneathĀ the radial field, will reduce the chance of picking up RF and moving it into the shack. Ā I will of course cleanĀ theĀ RF off the cables prior to movingĀ intoĀ the shack anyway… Ā This concludes Part I: The Beginning. Ā Next will be the construction/tuning of the first 40 meter vertical…
09/03/14:
Note:Ā There will be no part II, using these antenna. Ā I have come to the conclusion that phasing a set of GAP Challengers isĀ too difficult a project. Ā Even defining where the feedline is located is difficult and took a call to the maker. Ā I will be switching to feeding a pair of mono-bands Gaps on 30 meters. Ā Antenna “A” should arrive next Friday. Ā I will get it working prior to winter setting in, and i possible across winter, but more than likely next summer.
08/26/15:
Note: After about a year of testing, the 30 Meter Mono GAP is working so well, I will be moving forward with the 4-Square array. Ā Antenna 2 will be purchased later this year, and installed across winter/spring 2016.
Sponsors