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Their work was preceded by the description of velocity modulation by A. Arsenjewa-Heil and Oskar Heil (wife and husband) in 1935, though the Varians were probably unaware of the Heils' work. [ 6 ] The work of physicist W. W. Hansen was instrumental in the development of the klystron and was cited by the Varian brothers in their 1939 paper.
An amateur radio propagation beacon is a radio beacon, whose purpose is the investigation of the propagation of radio signals. Most radio propagation beacons use amateur radio frequencies. They can be found on LF, MF, HF, VHF, UHF, and microwave frequencies. Microwave beacons are also used as signal sources to test and calibrate antennas and ...
Hallicrafters founder William J. Halligan depicted in a 1944 magazine ad. William J. Halligan (1898–1992), founded Hallicrafters Company in Chicago in late 1932. Prior to this, he had been involved in radio parts sales for some years but decided the time was right for a handcrafted amateur radio receiver - the company name being a combination of Halli(gan) and (hand)crafters.
Practical antennas at these frequencies are much shorter than the wavelength, making it difficult to efficiently radiate much useful power. By current U.S. and Canadian regulations, LowFER transmitters may not have antenna and feed line lengths longer than 15 metres (49 ft), or final RF stage input powers that exceeds 1 watt. [6]
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
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The magnitude of the shift is a function of the wavelength of the signal and the angular velocity of the antenna: S = r W / λ Where S is the Doppler shift in frequency (Hz), r is the radius of the circle, W is the angular velocity in radians per second, λ is the target wavelength and c is the speed of light in meters per second. [13]
Testing radio range is often a large component of these hobbies. Amateur radio is often used with packet radio to communicate at 1200 baud, using the Automatic Packet Reporting System back to the ground station. Smaller packages called micro or pico trackers are also built and run under smaller balloons.