Message-ID: <003301bf7104$7f0c8cc0$8db6490c@ckrouse_ra.spk.hp.com>
Reply-To: "Curtis Krouse" <ckrouse@worldnet.att.net>
From: "Curtis Krouse" <ckrouse@worldnet.att.net>
To: <lancair.list@olsusa.com>
Subject: Re: antenna splitters/duplexers
Date: Sun, 6 Feb 2000 16:44:29 -0800
Mime-Version: 1.0

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Jim,

I'll try to clarify some terminology for you.  There is a difference between
a splitter, duplexer, and a coupler, however most of them look the same.  If
you have a component with one input and two outputs it can be either a
splitter or a coupler.  The differences are:

Splitter:  one input for the RF signal, two outputs for the RF signal.  The
two outputs have very little loss in addition to the typical 3db (50%) loss
of signal at each output port.  If you use the splitter in reverse (use the
outputs for inputs and the input for an output) you get tremendous loss of
your signal and may burn the splitter up.  So, the typical way to use a
splitter is to put one radio input into the input and to route the two
outputs to two antennae.

Duplexer:  think of the splitter backwards.  Low loss from both inputs to
the single output port, but good isolation between the two inputs one to the
other.  Typical use would be to put two radio inputs on the inputs, one on
each port and a single antenna on the output.  But, the difference is that
the RF signal is very well isolated from one input to the other.  If you
reverse a splitter, there is very little isolation from the two outputs and
a SWR (standing wave ratio) between the two outputs is high.

Coupler:  one input port for the RF signal, one output port for the RF
signal, and one or two coupled ports for the RF signal.  The coupler is
simply a component that can be connected to the inline RF signal with the
radio on the input and the antenna on the output with very little loss of
signal.  The coupled port or ports are for the purpose of sampling the RF
signal.  They typically have 20db of loss which will give you roughly .2% of
the RF signal (20Watts RF signal equals .2Watts coupled signal).  The
coupled ports are for sampling only and not for combining or splitting the
RF signal.

If one uses a duplexer for a stack radio and cables a handheld into the
second input port there should be absolutely no problem whatsoever with one
radio over powering the other and frying it's receiver.  The only time that
will happen is if the duplexer fails as a short from one input to the
other.....very rare.

I hope this helps.

Curtis Krouse N753K

>A while back, there was a discussion about splitting an antenna and leaving
>one end for a hand held. Some said it would fry the other radio, some said
no
>problem. Was there ever a verdict?

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