Message-ID: <1113338168.425c31390202f@webmail2.kuleuven.be>
Date: Tue, 12 Apr 2005 22:36:09 +0200
From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.ac.be>
To: rsgb_lf_group@blacksheep.org
References: <000701c53f43$2e3dd4d0$5f4136d2@mcalevey> <5.1.0.14.0.20050412154826.02288930@u0019445.kuleuven.be> <425BFCE8.9010004@usa.net>
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Hello Alberto,

phase coherence maybe a bit tricky.
I am not a mathematic expert, but just intuitive I would say that 
knowing the exact time of begin and end of a dot could be used to 
improve SNR.

One possibility that comes to my mind :
Assume
* a series of dot sequence (let's say 5 = .....)
* a dot length of 1 minute
* each dot starts exactly at the full minute
Now take one FFT every second, with the samples from the last 60 
seconds. the subsequent FFT's should show a triangular wave that has a 
period of 2 minutes and is in phase to the minute rytme.
Maybe using the right technique (kind of FFT of the FFT ?) one could 
detect this 2 minute triangular wave at signal levels that are to weak 
to bring up the dots with ARGO or similar software.

Makes this sense or it is just a stupid idea ?

73, Rik

Citeren Alberto di Bene <dibene@usa.net>:

> 
> > "TX/RX synchronisation" would reduce the time occupied by FFT by
> 100 
> > or more (from several FFT/sec to 1 FFT/min). The "calculation
> power" 
> > that becomes available could be used to improve SNR. But How ?
> 
> Maybe, if the Tx and Rx can be brought into phase coherence (what
> about 
> ionospheric effects ?)
> then the FFT could be replaced by techniques working in the time
> domain, 
> like correlation and
> Wiener or matched filtering... maybe someone more expert than me on
> the 
> subject would comment.
> 
> 73  Alberto  I2PHD
> 
> 
> 
>