This is a updated collection of easy to build projects for radio amateurs and swl's. See all my projects in the older posts down this blog. Have fun. 73 John
Sunday, July 24, 2011
No ground antenna for backpackers, balconies or plastic car bodies
A common problem with backpacker or balcony antennas is finding a good counterpoise. Also cars and caravans with a plasic body are a problem. Althow nothing beats a set of resonant radials, the shown solution offers a 1/4 wave stub that wil create an artificial counterpoise. The mobile antenna mount must be isolated from any metal by a epoxy or plastic plate and a normal T-Connector is used at the antenna feedpoint. Be shore to shortcut the end of the stub. The length of the stub in meters equals 1/4 Lambda x 0.66 (this is the velocity factor of 50 Ohm RG-58 ) or can be calculated by deviding 50 by the frequency .So if you need a stub for 14 MHz the outcome is 3.57 m. but this length is not critical. The setup can be easily mounted on top of a rucksack. On a balcony the stub can be layd on the floor.