The Providence Journal has a fascinating piece on the little known story of domestic radio surveillance during WWII. The Intelligence Division of the FCC selected several sites in the U.S. to set up monitoring stations to listen for enemy spies. A wartime short movie featured the radio surveillance effort. The […]
DF
8 posts
I’ll be presenting a paper, “On the Origins of RF-Based Location,” at the 2011 IEEE Radio and Wireless Symposium this morning at 8:00 in room Cira A. The paper collects together the pre-WWII material I’ve blogged about under the History of RF-Based Location category here at ÆtherCzar. This paper will provide […]
High Frequency Direction Finding (HF/DF or “Huff-Duff”) played a critical role in the Second World War. Shore based DF determined the location of German U-boat packs enabling convoys to be routed around them. Ship and airborne DF in conjunction with centimetric radar enabled effective antisubmarine warfare. [1, 2] One of […]
Under optimal conditions during daylight hours, direction finding (DF) accuracy could be as good as one to two degrees (300m at 10km range). [[1]] At night, however, the ionosphere reflects distant signals from over the horizon. The resulting “skywave” signals have a mix of vertical and horizontal polarization components that […]
Ettore Bellini (1876-1943) and Alessandro Tosi devised a much improved direction-finding system in 1907. [[1]] Their scheme deployed two orthogonal arrays similar to those of Stone. The key advantage of the Bellini-Tosi direction finder was a rotating transformer coupling. Rather than rotate a potentially large antenna system, the Bellini-Tosi system […]
John Stone Stone (1869-1943) patented the first effective direction finding system in 1902. [[1], [2]] Stone’s scheme involved a two element antenna with a first element (V) arranged no more than a half wavelength away from a second element (V’). The Figure below shows Stone’s invention. The two elements are […]
Communications may have been the first commercial application of wireless technology, but Real-Time Location Systems (RTLS) were close behind. In the first few years of radio, a variety of aggressive inventors recognized the problem of RTLS and leaped to offer solutions. Some of their ideas illustrated the inventors’ misunderstanding of […]
A few quick picks: A new radio direction finding system for deployment on Humvees was introduced last week by Southwest Research Institute. Claire Berlinski reporting in City Journal reports a surprising lack of interest in a couple of Russian exiles with copies of the Kremlin’s secret archives needing translation and […]