Remote controlled loop – a little magic.
Loop antennas are great for radio listening, particularly on the lower shortwave, medium wave (AM) and low frequency (LF and VLF) bands. One reason is that they are very directional. Another is that they are very small compared to the size of regular antennas used for transmitting and receiving on these frequencies. Normal antennas for these bands are hundreds of feet long or high. Loops for these bands are a few feet square at most.
But the ability to remote control a loop has advantages. First, although their size is relatively small, they are still pretty cumbersome. Second, although they do work in your house, they work much better outside. This is because there is less interference from household electrical wiring.
The picture on the left above shows an operator in a snowy field working a portable loop antenna and receiver. This 1927 picture is taken from my book on Wireless Direction Finding. Yes, the man is indeed wearing a suit as he sits on a stool in the snow playing with his radio! Sigh.
Remote Controlled Loop circa 1927 versus today
The picture on the right shows perhaps the ultimate remote controlled loop taken from Wikipedia. It is the British Post Office radio direction finding lorry, which was used in the 1920’s to track down illegal amateur radio transmitters (oh dear!) Can you see me standing on the roof of our Highlander turning the antenna while my wife drives me around town?
Actually, the whole history of wireless direction finding is fascinating. It was and is used by airplanes for navigational beacons, for finding and navigating ships at sea, and for triangulating on spies in the homeland as they transmitted information abroad.
My next project is going to be building a much more modern remote controlled loop. I will tell more shortly.