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Re: LF: Phase meter for propagation experiment

To: [email protected]
Subject: Re: LF: Phase meter for propagation experiment
From: "James Moritz" <[email protected]>
Date: Thu, 11 Apr 2002 12:41:42 +0100
In-reply-to: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Dear Wolf, Alan, LF Group,

I think I can set up this kind of experiment and leave it running fairly easily - but a couple of queries:
Signals like MSF have on-off keying. Feeding this signal into a digital
divider , the counting process will come to a stop when the signal level
falls below some threshold, so output from the divider will start and stop
at points in the cycle which depend on the amplitude of the input. So the
effect of dividing this signal to an audio frequency will be to introduce
more or less random jumps in phase each time the signal is keyed, even
though the original signal is phase coherent. Can the calibration software
cope with this? If not, a signal with a continuous carrier will be needed
for the reference - perhaps Droitwich on 198kHz will do.
Also, what signals do you plan to monitor? I expect the FSK and PSK signals
would be quite difficult, because both receiving stations would have to
track all the phase variations at the modulation rate, and store a vast
amount of data to allow the relative phase to be compared - a high degree
of timing accuracy (<1ms) would also presumably be required. Stations like
DCF39 would be much easier since they are CW most of the time, but even
here there is a jump in the phase every few seconds, so timing accuracy of
the order of 1 second would be required for the two RX stations to compare
the phase - still needing some work to achieve.
Cheers, Jim Moritz
73 de M0BMU




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