What frequencies are used?
Radio astronomy theoretically concerns cosmic signals at any frequency less than the frequencies of light. A wavelength is the distance traveled through space by the wave during of a single oscillatory cycle. The wavelength, rather than the frequency, (frequency = vibrational rate with respect to time), is often used to describe radio waves above one megahertz or so in frequency. Higher frequencies translate to shorter wavelengths. The relationship between the two measurements is set by the speed of light. wavelength in meters = 300/ frequency in megahertz. You will often, for example, hear the molecular hydrogen line frequency region of 1,420 megahertz refered to as the 21 centimeter band. There are practical limitations to our ability to receive many of these frequencies, especially from our protected position beneath the shield of the earth’s atmosphere. Frequencies below 15 Mhz or so, are rarely used due to absorption of these waves by the ionosphere. At the upper end of the freque
Except for a few early units, X band (10.525 GHz) was the only frequency used for police radar until the mid 1970’s. In 1976 radar guns using K band (24.150 GHz) were introduced; this led to the development of the first dual band (X/K) radar detectors. A proliferation of radar guns using Ka band frequencies began in 1987 with the introduction of photo radar (34.3 GHz) and was followed by the Stalker (34.2 – 35.2 GHz) in 1991 and the BEE 36A (33.4-34.4 GHz) in 1992.
