Small form factor, light weight, hand held radio direction finding antenna. An overall size of 13x13 inches and around 150g with installed battery makes fox hunting more fun.
Great for walking around or in small spaces. Works on a regular 9V battery with on-board holder, BNC connector and 3D-Printed handle.
The operation is quite simple. An electronic switch, formed from two diodes alternately forward-biasing which connects one of two antennas to the feed line attached to the input of an FM receiver, tuned to the desired frequency of interest. Antenna switching is done at and audio rate at around 1KHz. If one antenna is closer to the interference source, it receives the wave at a fraction of a second earlier then the other antenna. This accomplishes a phase difference between the signals received by the antennas. This switching action imposes a phase modulation which will be heart as a tone coming from you receiver.
When rotating the antenna perpendicular to the signal direction, both antennas receive the signal simultaneously thus no phase difference occurs and the audio tone disappears.
Simply, it works by nulling rather then peaking the signal.
Please contact me if you require more then showing available. I might have more available.
*Battery not included*