Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

LF: Re: Re: Long haul, suggestions

To: [email protected]
Subject: LF: Re: Re: Long haul, suggestions
From: "Andrew Talbot" <[email protected]>
Date: Thu, 20 Dec 2001 19:53:24 -0000
Reply-to: [email protected]
Sender: <[email protected]>
This is one of the arguments that have appeared on this reflector from time to time.  Producing the tones in a coherent manner as you suggest would have athe advantages you mention for ultra narrow detection, but this technique is using the signalling waveform in a way it was not intended !  To produce seven phase coherent on-off keyed tones would require seven locked oscillators - trivial when using a DSP approach to generate the waveform by just maintaining seven Numerical Controlled Oscillators in software and switching between their outputs, but very complicated to do with a direct RF generated carrier. 
 
I will run this again tomorrow and over part of teh weekend with a longer more meaningful message; the phase coherent GPS locked signalling is on hold for a couple of days so can carry on with this mode.
 
Andy  G4JNT
 
-----Andy, is it possible to let the TX run tomorrow (friday) evening ?
I would like to try again from the club station where the noise is much lower than here at home.

The strong local noise brought up this idea:

If the seven tones were transmitted in a "coherent" way (for each tone), so one could DETECT THE PRESENCE of such a signal (instead of decoding it) ? This way, if one used a waterfall with say 5-minute scrolling interval and a frequency resolution of a few millihertz, seven lines would grow out of the noise giving a coarse figure how many dBs are missing until DECODING is possible.
I once observed a CW qso between two stations with a very slow ("high-res") waterfall, one station produced a very sharp line on the display while the other (though very stable in frequency) did not. The same effect could be observed on Rik's proposed mode, depending on how the signals are generated... but I don't want anyone trying to key the output of seven independent DDS'es. There must be a smarter way (if the "coherent" transmission makes sense at all
<Prev in Thread] Current Thread [Next in Thread>
  • LF: Re: Re: Long haul, suggestions, Andrew Talbot <=