Farm History

WØAIH began building his contest station at the farm in 1977. To describe this amazing place is well beyond the scope of this article. See www.qth.com/w0aih for more details. Suffice it to say that a visit to the farm and operating a contest with the impressive collection of towers, Yagis, stacks, verticals, bobtail curtains, Beverages and more is an unforgettable experience. For years Paul dreamed about putting up a rhombic at the farm. That dream became reality shortly after he tried one out while operating the IARU HF World Championship Contest from K4VX in the 1990s. Paul put up his first rhombic, pointed toward Europe, using the basic design shown in Figure 1 (see PDF). The circumference of each rhombic is approximately 2150 feet. Each is fed with 7/8-inch HELIAX through a 10 kW balun (see Figure 2) he got at Dayton Hamvention. Additional scrounging produced the 600 ohm terminating resistors (see Figure 3) that Paul uses at the end of the rhombic opposite the feed point. Supports were two 90-foot towers and two 90-foot wooden poles at the four corners.

Paul used a multiwire rhombic design, constructing each antenna with two runs of #12 Copperweld wire spaced approximately seven feet apart. Based on the success of the European rhombic, it wasn't long before Paul had four rhombics in the air, covering Europe, Japan, Africa and Caribbbean. Figure 4 depicts he current configuration and approximate positions of the four rhombics at the farm. The rhombic pointed toward the Caribbean is at 45 feet, while the others are at approximately 100 feet.

Reversing Direction

Each rhombic is capable of switching direction. This is done by connecting open-wire (balanced) feed lines to the opposite ends of each rhombic; these are brought into a central switching box. Two remotely switchable DPDT relays allow the terminator and balun to swap positions. Figure 5 diagrams the switching arrangement, while Figure 6 shows the balun and terminator, as mounted on the ground between the two ends of the rhombic. Initially, Paul tried to reverse the direction of the Japan rhombic to hit the Caribbean, but he found that the antenna was simply too high for it to be effective in the opposite bearing. While three of the rhombics are two-wire designs, the Caribbean rhombic employs three parallel runs of #12 Copperweld wire. (Chapter 13 of The ARRL Antenna Book - 21st ed includes a discussion of rhombic design and construction considerations.)

Switching

Having operated at the farm, I can tell you that the rhombics are in high demand on 15, 20 and 40 meters at both the running and spotting positions. To make it possible to share the rhombics, Paul installed a five-position switch for each rhombic (see Figure 7). This switch is located in "the chalet," which houses all operating positions except 20 meters. If someone at one of the operating positions wants to use one of the rhombics, they put out a request on the CT "gab" network. For example, the 20 meter run operator might put out a message asking, "Can I have the Japan rhombic?" If nobody is using it, someone in the chalet switches the Japan rhombic to the 20 meter position. The Japan rhombic then becomes one of the available antennas at the 20 meter station - along with Yagis, stacks and so forth. It's a pretty simple system, and it works well.

For the complete version of this article as published in the NCJ, view the pdf version.