[Elecraft] Clean 600hz signal, full dsp decoupling possible?

[Geoffrey Mackenzie-Kennedy]

Hello Dick,

I am not a DSP expert either, but a tracking filter keying an audio 
oscillator will do exactly what you want. In its simplest form a tracking 
filter is a phase locked loop, and ICs which can be used at audio for this 
purpose have been available since the 1960s and are inexpensive. Also a 
tracking filter working at audio can be connected to a receiver's low level 
audio output if one is not already in the receiver. I believe that the DSP 
wizards have already designed something that does the same job.

Tracking filters are very useful when searching for signals below the 
receiver's noise floor, at VHF for example, but listening to a keyed audio 
oscillator without noise can be quite boring.

73,
Geoff
GM4ESD



----- Original Message ----- 
From: "PA3CW" <pa3cw at planet.nl>
To: <elecraft at mailman.qth.net>
Sent: Saturday, October 17, 2009 8:57 PM
Subject: [Elecraft] Clean 600hz signal, full dsp decoupling possible?


>
> Hello forum friends,
> Not being an expert in the world of DSP, but being an experienced CW
> operator i often asked myself this question:  Why is there no full
> decoupling between the received signal and the tone in the headset or
> speaker? In other words is it possible that the dsp discrimiates enough
> between signal and noise and steers a clean LF oscillator making a clean
> 600hz or so tone?  Is such a setting possible or do i overlook something
> here? Just a little out of the box thinking...
> Dick PA3CW