Future Rhombic Plans
I have plans to rebuild my antenna farm. There are several compromises in the current 6 rhombic 210 ft per leg system:
The diagram above is an overhead view of 9 rhombics, 300 ft per leg with a 70 degree tilt angle (40 degrees a the feed point). There are 10 poles that hold everything up. The dot in the middle is a pole that serves as one side support for each of the rhombics laid into the outside of the circle. The 9 other poles are located every 40 degrees around a 439.7 foot radius from the center pole. 200 feet of dacron rope runs from the center pole to each rhombic. The center pole will be 15 feet higher than the outside poles to allow for the sag in the rope. Each outside pole serves as a feed point, end point and side support for three different rhombics in two horizontal plains separated by 5 feet. The top of each side support will look similar to this:
The difference will be that each feed/end point will have a feed line connected and there will only be two layers instead of three as in the picture. The feed line from the shack will go to a massive relay box located on the center pole. Two feed lines will run from the center pole to each of the outer poles, then up to the two rhombics with feed/end points. Each outer pole will be guyed to hold against the inward pulling strain. The relay box will have 36 DPDT relays, a feed buss and a terminating resistor buss. This will allow any rhombic to be feed from either end, terminated or not terminated, and multiple rhombics to be feed in phase.
I plan to use open wire line for most runs so moisture on the feed line shouldn’t change the tuner settings much. To reach my target height of 85 feet, I am going to experiment with joining poles together with C channel steel and bolts. With longer pipe on top. The new dimensions, 300 ft/leg with a 70 degree tilt angle will give me the following gain over a dipole on each band:
The pattern on 80 meters will look like this:
The pattern on 20 meters will look like this:
The pattern on 10 meters will look like this:
With 18 major lobes, I will have continuous coverage in any direction on each band below 15 meters. 12 and 10 will have some gaps but they will be minor.
This planed system will cover about 17 acres and cost less than $3000.00.
Is this excessive, obsessive, beyond the pale? You Bet! A voice in my head says:
"Build it and the DX will come."