Made this loop antenna for locating small radio beacons (there will be a post about these soon). It is made of 2 meters of heavy copper wire looped into 1 turn and tuned with a 1-5pF capacitor. The wire is supported inside a loop made of PVC tube. The loop is tapped at about 1/5 of the loop and fed to a scanner radio.
The beacons transmit keyed RF morse code so the scanner operates in CW mode thus forming a 400Hz beat tone with the incomming RF. By waving the loop around and listening to the amplitude of this tone it is possible to find the direction of the incomming signal.
This is the first in a series of experiments in RDF.