Output duplexers

Rather than use a lossy expensive RF relay on the output of the DATV transmitter we can use a duplexer (for just 146 and 437 MHz operation) or a triplexer filter - as well as providing automatic band switching the duplexer (or triplexer) provides some bandpass filtering on the transmitter output!

The duplexr / triplexer can be a standard unit as we all use to run a dual band VHF / UHF rig in to a dual band antennae up one co-ax or they are very simple and cheap to build - links and circuits are available on this page:

• I1WQR's page has several links to easily constructed duplexer designs - including one by Tony G3KTU.