Duplex switch

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Frequency plan of the duplex remote stations

Relay station uses duplex operation

Duplex filter as a passive low-pass high-pass filter

A duplex switch is used in duplex radio devices to connect the radio antenna to the transmitter and receiver at the same time. The prerequisite is the use of a duplex channel, i.e. a frequency pair in which the transmission and reception frequencies are offset by a fixed duplex distance. These two frequencies are then called the upper and lower bands.

Some exemplary radio applications which, among other things, can use duplex switches:

• Amateur radio service
• Commercial radio
• BOS radio
• Analog train radio
• Marine radio
• Historical radio telephone networks such as the A-Netz , B-Netz and C-Netz in Germany

Because of its size, a duplex switch is usually only built into fixed stations or mobile radio devices that are portable to a limited extent .

In the BOS radio in the mobile radio devices ( FuG -8b and FuG-9b) to increase the flexibility of the radio application, the switch is not permanently coupled to the transmitter or receiver. A relay circuit can be used to switch the turnout depending on the type of operation and traffic selected. These four circuits are possible:

BOS radio

abbreviation	function	description
W / U	Intercom subband	The transmitter and receiver alternately use the sub-band output of the duplex filter. The device does not work in duplex mode at all, but in simplex mode (e.g. at the point of use).
WHERE	Intercom upper band	The transmitter and receiver use the upper band output of the turnout.
G / U	Double talk subband	Transmitter in the lower band, receiver in the upper band
G / O	Intercom upper band	Transmitter in the upper band, receiver in the lower band

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  Historically: open A-network radio telephone with duplex switch, transmitter and receiver modules

• 

  BOS duplex switch made of AEG Teledux-9-80. Above a coaxial cable each for transmitter and receiver, via the flat cable switching of the operating mode, below antenna output

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  VHF base station switch for 19 "cabinet with internal reflectometer and standing wave measuring device on the front panel, make Kathrein

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  Motorola Mototrbo Relay DR3000 with antenna splitter mounted in a flight case ready for use

Web links

• Report on the dimensioning of duplex switches in relay stations (PDF; 3.9 MB)
• Report on the practical construction of a low-budget duplexer in the Netherlands by PA0NHC

literature

• WB Bryson: Design Of High Isolation Duplexers And A New Antenna For Duplex Systems . IEEE Transactions on Vehicular Communications, 1/1965, 134-140.
• Edward P. Tilton, W1HDO: A Trap-Filter Duplexer for 2-Meter Repeaters . QST 3/1970, 42-46
• John J. Bilodeau, W1GAN: A Homemade Duplexer for 2-Meter Repeaters . QST 7/1972, 22-26, 47
• Mitsuo Makimoto; Haruyoshi Endoh, Sadahiko Yamashita: Compact Duplexer For 400 MHz Band Land Mobile Radio Equipment . Vehicular Technology Conference, 1983. 33rd IEEE. 1983, 201-204.
• JS Gurske, K9EYY: A Home-Brewed Six-Cavity Duplexer . ham radio, 2/1985, 12-27
• Sam Jewell, G4DDK: Procom Repeater Duplexers . RadCom, September 2009, 58-59
• William G. Moneysmith, W4NFR: A Homecrafted Duplexer For The 70 Centimeter Band . QEX - September / October 2009, 10-16