A combiner is generally a broadbanded device that simply combines two or
more signals together while (hopefully) providing an acceptable impedance
match to all devices. A diplexer is generally a filter and combiner
combination that passes specific frequencies and suppresses undesired
frequencies at the various inputs and outputs of the diplexer.
For instance, you can use a two way transformer type splitter/combiner to
combine a 145 MHz and a 440 MHz signal on to one coax. Once this is done,
both signals will be present on the feedline but some (a great deal,
actually) of the 145 MHz signal will be present at the 440 MHz input and
vice versa. (there will be some losses experienced by either signal due to
the properties of the splitter/combiner) With a diplexer, filters are
installed together with the combiner to suppress the 145 MHz on the 440 MHz
input, as well as the 440 MHz at the 145 MHz input. Both signals will be
present at the combined output. The diplexer can be turned around to
separate the signals by filtering the opposing frequency from each of the
outputs. Hence, the 144 MHz will be present at one output and the 440 MHz
output at the other, all from a common input.
Keep in mind that when I say that the 144 MHz or 440 MHz signal won't be
present at the opposite input or output, what I mean is that it will be
significantly suppressed. The amount of suppression will depend on the
quality, number, and alignment of each of the filters.
A duplexer generally refers to a two channel (or frequency) diplexer while a
diplexer in general refers to diplexing of two or more frequencies.
73,
Scott M.
Post by Dr. Anton Squeegeesays...
Post by LunarayWhat is the difference between these two devices? Do they do the same
thing? Thanks!
No, quite different actually. A combiner allows multiple
transmitters to share a single antenna simultaneously. A duplexer allows
a repeater to use a single antenna for simultaneous transmit and
receive.
With that said, duplexers and combiners can be ... well,
combined... to provide both functions in one cabinet. This is often the
case with trunked radio systems.
--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
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http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)
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