Topband: TRANSCEIVER WITH SEPERATE RECEIVER?

[Jim Brown]

On Mon, 12 Apr 2004 19:23:07 -0700, wb6tza at socal.rr.com wrote:

>There are boxes
>to mix and switch the rx audio feeding the headphones...  having one
>rx in phase and one out of phase can bring some startling results,
>especially with the two receivers are fed from different antennas

VERY important distinction -- what do you mean by "in phase" and "out
of phase?"  Phase is a continuous function having an infinite number of
values, and is proportional to frequency.  Any network that modifies
the phase of a signal path will do so to a degree that varies with
frequency. RF phase shift networks and antenna spacing takes advantage
of these differences to achieve directivity.  

Do you really mean that you are inverting the POLARITY of the audio
signal of one of the receivers and adding it to the audio from the
other receiver?  Polarity is very different from phase -- it has two
values, + and -, or "normal" and "inverted,"  and it is NOT a function
of frequency. This can be done with a gain stage, with a transformer,
or even by reversing the wiring of balanced I/O. But if it is done
well, there is NO change to the phase. 

Or do you mean that you are inverting the polarity of the RF signal?  

Or do you mean that you are shifting the phase of the RF signal to some
varying degree (as in the ANC-4 noise cancelling unit), then adding the
phase shifted signal to another signal to null interference? 

ALL of these techniques are potentially useful, but they are quite
different. 

Jim