TO: ALL WOOD COUNTY ARES MEMBERS (OFFICIAL)
ALL ARES AND NON-ARES AMATEURS ANYWHERE (INFORMATION)
FROM: KEN HARRIS WA8LLM ARRL DISTRICT 3 EMERGENCY COORDINATOR
WOOD COUNTY EMERGENCY COMMUNICATIONS INC.
WOOD COUNTY ARES BULLETIN NR 17.47 DATE: November 19, 2017
SUBJECT: DIPLEXER VERSES DUPLEXER
Diplexer and Duplexer sounds like they are the same type of device, but they aren't. The devices described here are used in RF or Radio Frequency, in antenna circuits. Both devices do the same thing, but in a different way. Both devices are used to either combine two or more antennas to one radio, or combine two or more radios to one antenna.
The Duplexer is used when both frequencies are in the same RF band. The Duplexer is mostly used on repeaters. Most repeaters use one antenna, one receiver, and one transmitter. The receiver needs to be able to receive signals while the transmitter is transmitting. Since repeater frequencies aren't spaced very far apart the Duplexer needs to be very selective so the Transmitter doesn't interfere with the Receiver.
The Diplexer is used when there are two different frequency bands being used at the same time, such as 146 MHz and 440 MHz. The Diplexer is handy when both frequency bands are in one radio, but two different antennas are being used. One antenna might be a 146 MHz Ground Plane and the other one a 440 MHz Beam antenna. The Diplexer doesn't need to be as selective as the Duplexer since the frequencies are spaced far apart.
Ken Harris WA8LLM
Wood County WV