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High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate over long distances; for example, between U-boats and their land-based headquarters.
Motorola T5320 FRS handheld radio. The Family Radio Service (FRS) is an improved walkie-talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies around 462 and 467 MHz in the ultra high frequency (UHF) band.
A portable, battery operated GT-302 Accumatic automatic direction finder for marine use. Radio direction finding, radio direction finder, or RDF, was once the primary aviation navigational aid. (Range and Direction Finding was the abbreviation used to describe the predecessor to radar. [2])
The simplest klystron tube is the two-cavity klystron. In this tube there are two microwave cavity resonators, the "catcher" and the "buncher". When used as an amplifier, the weak microwave signal to be amplified is applied to the buncher cavity through a coaxial cable or waveguide, and the amplified signal is extracted from the catcher cavity.
A great advance in RDF technique was introduced in the form of the Bellini-Tosi direction finder (B-T) system, which replaced the rotation of the antenna with the rotation of a small coil of wire connected to two non-moving loop antennas. The loop antennas were similar to those used in earlier systems but fixed in position, set at right angles ...
MFJ Enterprises, founded in 1972 by Martin F. Jue, is a manufacturer of a broad range of products for the amateur radio market. They specialize in station accessories, such as antenna tuners and antenna switching equipment. As of 2014, MFJ was responsible for manufacturing more amateur radio products than any other company in the world. [2]
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UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals. As the visual horizon sets the maximum range of UHF transmission to between 30 and 40 miles (48 to 64 km) or less, depending on local terrain, the same frequency channels can be reused by other users in neighboring geographic areas (frequency reuse).