The Small Loop Project
I have been thinking about getting a decent loop antenna for whenever we travel away from home. After a short engineering meeting with my dog, cat, and ferret, we decided on a few basic design parameters.
1. It has to be small - about a half-foot or less.
2. It should tune from below AM broadcast to about 4 MHz (75/80 meter ham band).
3. It needs to be gimbal mounted to allow pan & tilt movement (azmuth and elevation planes).
4. It should be selectably "active" with an amplified gain/attenuate control.
Here's where it starts. I cut a 5 inch cardboard mailing tube to 1 inch width. Other materials could be PVC pipe kind'a heavy), nylon strip (flexable, but fragile), or wood (hex, octagon, square). I wound 23 turns of No. 18 enameled copper (magnet wire) for a total inductance of 122 uH. This will resonate with 1,000 pF down to 450 kHz and up to about 4 MHz at around 10 pF. Cool.
A closeup of the "basement shop" construction. Although not much to look at, it's very sturdy. After winding the wire, I secured the turns with electrical tape and gave the entire assembly two good soakings in marine epoxy. The epoxy soaked into the cardboard and in, and around, all the windings. Not shown is Bowser who thinks this is a kitty toy.
Posted on March 25, 2006.
More next week.
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