222 MHz Cheap Yagi
Home Brew 222 Mhz 6 Element Yagi
If you're planning to build an EME array, don't use these antennas. But if you want to put together a
VHF Rover with less than $500 in the .antennas, read on.
The simplified feed uses the structure of the antenna itself for impedance matching. So the design
started with the feed and the elements were built around it. Typically a high gain antenna is designed in the
computer, then you try to come up with a driven element matching arrangement for some weird impedance.
In this design, compromises for the feed impedance, asymmetrical feed, simple measurements, wide
bandwidth, the ability to grow with the same spacing, and trade offs for a very clean pattern cost about 112
dB of gain. But you can build these antennas for about $5 ! ! ! !
The antennas were designed with YagiMax, tweaked in NEC, and the driven elements experimentally
determined on the antenna range.
The boom is 314" square, or 112 X 314" wood. The elements have been made from Silicon Bronze
welding rod, Aluminum rod, Hobby tubing, and solid ground wire. You really want to solder to the Driven
Element. Silicon Bronze Welding rod, Hobby tubing, and #10 or #12 solid copper wire have been used to
make the driven element. A drop of "Super Glue", Epoxy, or RTV is used to hold the elements in place.
Theory y~u don't see any gamma matches. shorting bars. tnmmer caps. or any other adjustments on the driven element. We are usingthe structure of the Vagi itself lor impedance matching. It's a simple technique. A dipole has roughly 72 ohms impedance when it's in free space. As other elements.or even the ground,approach the dipole. its impedance is lowered. Put the other elements at just the right distance and you can get a direct match to 50 ohms. This works and is simple enough , but you can't get the elements close enough to couple much