In the winter of 2002, I relocated my family from our small ranch in the southeast corner of Wyoming to the south Denver suburbs. For my hobby, it was a difficult relocation as I had to give up my antenna farm made of numerous towers, antennas and, in particular, my 4 square arrays for 40 and 80 meters. These arrays were used primarily for my own science studies regarding short and long path DX propagation during the winter months.
By relocating, I was going from 160 acres to a home development lot that offered a backyard that was only 40 feet wide by 86 feet long. My front yard was 20 feet higher in elevation than my backyard, somewhat putting my backyard antenna location in a hole. I knew that my low-band days using arrays were over. But at least I had zero covenant restrictions against antennas. Thus, my mulling began as soon as we unpacked, mainly trying to figure out a way to install an 80-meter bidirectional array.
For the past two years I tried to work the long path propagation with a single vertical with no luck. I had some success trying various antennas for DX QSOs on the short path, but I could not hear weak signal DX being reported either way. Suffering from S9+ ambient RF interference made it nearly impossible to work anything worth mentioning.
So, I decided to do some things in the shack. It started with replacing my existing rig with an ICOM IC-756 Pro III with its new noise reduction technology. My ambient noise levels were cut on average by 2 S-units and the noise reduction was very helpful in pulling out DX.
Then, I was intrigued by the new antenna that Cushcraft was introducing. It was called the MA8040V. It was designed to be small, quiet, self-supporting, effective and able to take at least 1.5 kW on either SSB or CW. It offered two bands: 80 and 40 meters. That was all I needed to hear. Soon after, I ran to Ham Radio Outlet here in Denver and checked things out.
The Cushcraft MA8040V is a very well thought-out product. Per Cushcraft, it is a compact dual-band monopole vertical antenna that features automatic bandswitching for the 40 and 80 meter bands. Independent top-mounted resonators are configured in parallel for negligible cross band interaction. Each resonator uses a combination of capacitive and inductive loading that has been proportioned to optimize efficiency and provide a favorable feed-point SWR.
Tuning the antenna is fairly simple. The adjustable top-section stinger is used for 80 meters. Some fine tuning on 80 meters also can be done by adjusting the length of the eight capacitance rods directly below the 80 meter coil.
Forty meters is tuned only by adjusting the lengths of the four capacitance hat rods directly below the 40 meter coil. I did not notice any effect on either band's SWR by tuning the other.
The MA8040Vs are small in size, self supporting anywhere from 23-27 feet, with large 2.5-inch loading coils that use #12 copper wire for high efficiency and power handling capability. Each coil is wisely encapsulated with a tough UV resistant Anchor Seal epoxy that introduces negligible RF loss and provides critical weather protection.
The antenna is built to survive. The 21 foot main radiator elements are made of T6061-T6 0.058-inch wall aluminum tubing. RF-current distribution along this portion of the array would be relatively uniform with no intervening structures to introduce loss. Even all the hat rods were well thought out. For both bands, the hat rods are made of resilient 0.1-inch tempered stainless steel that will resist damage from environmental hazards.
For DX, the design of the antenna provides a low take-off angle to favor working long distances. The antenna has a high angle pattern null to reduce interference from local atmospheric noise and QRM. The antenna comes witha 400 foot roll of radial wire to help in setting things up. I thought this was a nice touch by Cushcraft. At my home, the antenna was at least one half to a full S-unit quieter in reception of ambient noise than my previous multi-band vertical.
The Array Journey Begins, But Challenges Ahead
Now with materials in hand, I had to install the initial antenna at least 7 feet back from fence line to meet our municipal code requirements. That was the only red tape I had locally. With an odd shaped lot, I was able to get as far away from my house as possible - right next to where all my neighbors parked along the street. It was over 20 feet from the home's foundation, but unfortunately further down into the hole of my backyard.
Getting the idea that I might actually be able to phase these antennas together for 80 meters, I measured out the distance to put up a second MA8040V. By just a few feet, I had enough room to put this antenna in place. But due to space limitations, it would have to be 6 feet from my house and next to my electrical box outlet. It also was near a clump of trees.
My reason for this spacing and orientation were simple. I had to space the antennas exactly east and west from one another since setting these up with an ideal NE/SW was not possible due to constraints of the yard.
For the complete version of this article as published in the NCJ, view the pdf version. K1ZM/VY2ZM's 2005 CQWW CW DX Contest on Topband from VY2ZM article is also available as a pdf version.