Another Weekend Antenna Project

This weekend I put together a couple of components – PVC pipe and aluminum pipe – as outlined in this article. The design is based on the micro vert that was published some time in Antennex, but of course, with a few tweaks. I decided to build one for 40 meters that would be useful for mountain climbing, hoteling, or just about anywhere I would be limited to a lighter load and other antenna restrictions.
I found in the micro vert design document that a specific coaxial cable length has to be calculated to form a counterpoise for the radiating system. Furthermore, he suggests an adjustable end-piece for the antenna to adjust the capacitance. Well, through experiment and investigation that suggests the coaxial feed cable may be a part of the radiating component, I’ve also found that design to be heavier and needless. Most people would stop and walk away from the design once it is suggested that the feed line would radiate, but I am more open minded. If we are only delivering 5 watts to the system, for some reason (to me exclusively) it makes sense to have the feed line help with radiation…. for some reason I can’t explain. So, if RG-8 coaxial cable with a velocity factor of .66 is cut to 6.9 meters (same length for RG58) – the electrical length of a quarter wavelength for 7.05 MHz – and the antenna is placed in free open space on the ground with one 18 inch loop formed in the coaxial cable as a balun, all analysis points check out to be an efficient antenna. At 7.05 MHz the antenna has 1.0 SWR with zero reactance!

Now the real part: does it get any QSO’s? Well, after spending the morning and early afternoon working on my design, I grabbed the keys to the car and packed all the tools, the antenna analyzer, a tripod stand, headphones, a quick dinner – I packed everything except the most important parts – and headed for the Yamanashi mountains. Barreled down the highway and exited at Otsuki, then cut up a mountain road toward Okutama Lake. After arriving, setting up the antenna, and getting settled, I decided it was time to sit down and listen/send some morse. That is when I realized that I forgot the transceiver, keyer, and iambic key! I turned everything upside down looking for it… to no avail. Going to give a try next weekend and post some pictures. If you read Japanese, this guy also has some interest micro vert assemblies.