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    ek hornbeck, Man Oh Man

    Frequency frogging repeaters were commonplace in frequency-division multiplexing systems from the middle to late 20th century.

    http://en.wikipedia.org/...

    repeater

    http://en.wikipedia.org/...

    frequency frogging

    In telecommunication, the term frequency frogging has the following meanings:

    The interchanging of the frequencies of carrier channels to accomplish specific purposes, such as to prevent feedback and oscillation, to reduce crosstalk, and to correct for a high frequency response slope in the transmission line.

    In microwave radio relay systems, the alternate use of two frequencies at repeater sites to prevent feedback and oscillation.

    Note: Frequency frogging is accomplished by having modulators, which are integrated into specially designed repeaters, translate a low-frequency group to a high-frequency group, and vice versa.

    A channel will appear in the low group for one repeater section and will then be translated to the high group for the next section because of frequency frogging.

    This results in nearly constant attenuation with frequency over two successive repeater sections, and eliminates the need for large slope equalization and adjustments. Singing and crosstalk are minimized because the high-level output of a repeater is at a different frequency than the low-level input to other repeaters.

    It also diminishes group delay distortion. A repeater that receives on the high band from both direction and sends on the low band is called Hi-Lo; the other kind Lo-Hi.

    http://en.wikipedia.org/...

    Microwave radio relay is a technology for transmitting digital and analog signals, such as long-distance telephone calls, television programs, and computer data, between two locations on a line of sight radio path. In microwave radio relay, microwaves are transmitted between the two locations with directional antennas, forming a fixed radio connection between the two points. The requirement of a line of sight limits the distance between stations to 30 or 40 miles.

    Beginning in the 1950s and 1960s networks of microwave relay links, such as the AT&T Long Lines system in the U.S., carried long distance telephone calls and television programs between cities. These included long daisy-chained series of such links that traversed mountain ranges and spanned continents. Much of the transcontinental traffic is now carried by cheaper optical fibers and communication satellites, but microwave relay remains important for shorter distances.

    http://en.wikipedia.org/...

    Microwave Radio Relay

    How microwave radio relay links are formed

    Because the radio waves travel in narrow beams confined to a line-of-sight path from one antenna to the other, they don't interfere with other microwave equipment, and nearby microwave links can use the same frequencies. Antennas used must be highly directional (High gain); these antennas are installed in elevated locations such as large radio towers in order to be able to transmit across long distances. Typical types of antenna used in radio relay link installations are parabolic antennas, dielectric lens, and horn-reflector antennas, which have a diameter of up to 4 meters. Highly directive antennas permit an economical use of the available frequency spectrum, despite long transmission distances.

    Over-horizon microwave radio relay

    In over-horizon, or tropospheric scatter, microwave radio relays, unlike a standard microwave radio relay link, the sending and receiving antennas do not use a line of sight transmission path. Instead, the stray signal transmission, known as "tropo - scatter" or simply "scatter," from the sent signal is picked up by the receiving station.

    Signal clarity obtained by this method depends on the weather and other factors, and as a result a high level of technical difficulty is involved in the creation of a reliable over horizon radio relay link. Over horizon radio relay links are therefore only used where standard radio relay links are unsuitable (for example, in providing a microwave link to an island).

    Though not commonly known, the US Military used both portable and fixed-station microwave communications in the European Theater during WWII.

    Starting in the late 1940s, this continued to some degree into the 1960s, when many of these links were supplanted with tropospheric scatter or satellite systems.

    When the NATO military arm was formed, much of this existing equipment was transferred to communications groups.

    The typical communications systems used by NATO during that time period consisted of the technologies which had been developed for use by the telephone carrier entities in host countries.

    One example from the USA is the RCA CW-20A 1–2 GHz microwave relay system which utilized flexible UHF cable rather than the rigid waveguide required by higher frequency systems, making it ideal for tactical applications.

    The typical microwave relay installation or portable van had two radio systems (plus backup) connecting two LOS sites.

    These radios would often provide communication for 24 telephone channels of frequency division multiplexed signal (i.e. Lenkurt 33C FDM), though any channel could be designated to carry up to 18 teletype communications instead. Similar systems from Germany and other member nations were also in use.

    Similar systems were soon built in many countries, until the 1980s when the technology lost its share of fixed operation to newer technologies such as fiber-optic cable and communication satellites, which offer lower cost per bit.

    Microwave spying

    During the Cold War, the US intelligence agencies, such as the National Security Agency (NSA), were reportedly able to intercept Soviet microwave traffic using satellites such as Rhyolite.

    Much of the beam of a microwave link passes the receiving antenna and radiates toward the horizon, into space. By positioning a geosynchronous satellite in the path of the beam, the microwave beam can be received.

    Hostage tactics are for those who can’t win their fights through elections, in Congress, in fights for the Presidency or in the Courts. It is a last gasp of those who cannot cope with the realities of our democracy. ~ Senator Elizabeth Warren

    by anyname on Thu Oct 03, 2013 at 01:47:49 AM PDT

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