"Jeremy Salch" wrote in message
...

I have one which has a input for 0-90Mhz then 120-500Mhz on the other
side,
and it puts them both onto one coax line. Is that called a duplexer as
well
or is it called something else ?

'Duplexer' is a term used to describe devices that provide greater isolation
between the ports than what you seem to have. They are used on repeater
stations where the transmitter and receiver operate simultaneously on
frequencies close together. The transmitter is producing anywhere from a few
watts to several hundred watts, and the receiver cannot be 'desensed.' The
duplexer acts as a sharp filter as well as a combiner, allowing both units
to use the same antenna.

There are other names for similar devices, which vary in sophistication. The
simple TV-antenna splitter allows two receivers to use a common antenna, but
you don't get much isolation between the output ports and you wouldn't
transmit much power through one. There are power splitters and combiners
that you can buy or build. As you have not stated the application it is
impossible to tell you what you need. Could you be more specific about what
it is that you are intending to do with this device?

"PM"