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For this reason, Doppler DF systems normally mount their antennas on a small disk that is spun at a high speed using an electric motor. Performing the same calculation using an antenna mounted to a disk with a diameter of 50 centimetres (20 in) diameter spinning at 1000 Hz results in: S = .25 × 1000 × 101.8 / 48 = 530 Hz
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.
Radio direction finding equipment for eighty meters, an HF band, is relatively easy to design and inexpensive to build. Bearings taken on eighty meters can be very accurate. Competitors on an eighty-meter course must use bearings to determine the locations of the transmitters and choose the fastest route through the terrain to visit them.
Maxwell K. Goldstein (January 15, 1908 – February 18, 1980) was a first generation Jewish-American scientist and engineer who was instrumental in the development and deployment of high-frequency direction finding by the United States Navy during the Second World War.
He designed an exceptional radio antenna which enabled effective high frequency (HF) radio direction finding systems to be installed on Royal Navy convoy escort ships. [1] Such direction finding systems were referred to as HF/DF or Huff-Duff, and enabled the bearings of U-boats to be determined when the U-boats made high frequency radio ...
An intense solar storm causing aurora borealis (northern lights) will also provide occasional propagation enhancement to HF-low (6-metre) band radio waves. Aurorae only occasionally affect signals on the 2 metre band. Signals are often distorted and on the lower frequencies give a curious "watery sound" to normally propagated HF signals.
The array consisted of a ring of 120 vertical monopoles covering 2–20 MHz. Tall wood poles supported a 1,000-foot diameter (300 m) circular screen of vertical wires located within the ring of monopoles. His research is still used today to guide the design and site selection of HF/DF arrays. Records of his research are available in the ...
A valve RF amplifier (UK and Aus.) or tube amplifier is a device for electrically amplifying the power of an electrical radio frequency signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers during the 1960s and 1970s, initially for receivers and low power stages of ...