Duplexer and Repeaters: Basic Information
Duplexers and Repeaters Some Basic Information
BY ROBERT A. LEHNING*, WA2YSJ
All across the country there are many amateur repeate stations operating on 2 meters, 220 and 440 MHz, and to some extent on 1.2 GHz. Several modes of operating such as FM, ATV, and packet (digital) have also become very popular. Many amateur radio operators use these repeaters but do not really understand the basics of duplexers or the role a duplexer plays in repeater operation.
It is common knowledge that if you “hit” a repeater with low‐level signal such as a mobile or handheld radio transmits, the repeater retransmits the information at a higher power level over a greater area. This is commonly referred to as the range of the repeater, the area within which you can activate the repeater with the transmitted signal.
Antenna patterns can be adjusted so that a repeater range can cover a certain area or direction only, but a majority of repeater ranges are intended to be omnidirectional (see fig. 1). The repeater does this receiving on one frequency and retransmitting on another frequency. This occurs simultaneously and is called duplex operation. The frequency separation between the TX (transmit) and the RX (receive) is sometimes referred to as the split or repeater pair of frequencies.
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