Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!uunet!world!ksr!jfw
From: jfw@ksr.com (John F. Woods)
Newsgroups: sci.electronics
Subject: Re: Phone scrambler
Keywords: Phone scrambler
Message-ID: <2931@ksr.com>
Date: 1 Apr 91 18:56:56 GMT
References: <1991Mar23.215050.24738@sugar.hackercorp.com> <1991Mar24.012754.9816@athena.cs.uga.edu> <2476@umriscc.isc.umr.edu> <1991Mar25.021609.21539@athena.cs.uga.edu>
Sender: news@ksr.com
Lines: 14

mcovingt@athena.cs.uga.edu (Michael A. Covington) writes:
>A doubly balanced mixer outputs *only* sum and difference frequencies;
>neither the input signal nor the oscillator signal appears at the output.
>I think "doubly" refers to the fact that both the oscillator and the
>input can swing to either side of 0 volts and the balancing still works.

A doubly-balanced mixer is balanced with respect to the signal input and
the local-oscillator input; a singly-balanced mixer is balanced with respect
to only the signal input.  The input signal and the oscillator signal are
suppressed at the outputs (and the LO is also suppressed at the signal input
port, resulting in less leakage of LO energy to (for example) your antenna).
The ARRL Radio Amateur's Handbook or any other electronics text covering radio
(i.e. not some compugeek text which starts with gates and ends with ICs)
will have a nice explanation of just what this is all about.