My Wooden Airplane
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8/14/2013 - 8/19/2013

Comm Antenna, Part 1

One of the advantages of having a wooden airplane is that the antennas can all reside inside the fuselage, instead of sticking out into the slipstream. I decided I'd try to make a type of antenna called a coaxial dipole. I've made them before during my days as an active Ham Radio operator. I started with an old 1/4-wave whip antenna that someone gave me. I mated that to a piece of 3/4-inch copper pipe and an end cap. It turns out that it would just fit at the aft end of the baggage compartment. Unfortunately, when I tested it with an SWR meter, it came out awful! I suppose I could have damaged the antenna connector when I soldered the cap onto the end of the pipe. But I realized that even if the connector was still intact, this is a balanced antenna, and I'm feeding it with an unbalanced feedline (coax). Unless the length of coax was a perfect odd multiple of 1/4-wavelength, I'd need a device called a BALUN. (Some people also use ferrite beads, which serve the same purpose, but they convert energy into heat, which is inefficient.) I decided I needed to try something else.

Total Time: 16.0 hrs.