Re: LF: DFCW

[DL4YHF@aol.com]

Hello Rik and others,

Rik wrote
> 1. Using DCF77 (or similar) and the appropriate software (such as provided
> by DL4YHF) one can set the PC clock with a 1/10 second accuracy. 
> Even by
> setting the PC clock by hand an accuracy of better than 1 second can be
> achieved. So the PC's at both sides (TX and RX) can have their clock
> 'synchronized' at 1 second or better.

Well, the DCF77 decoder was a nice experiment, but not too much more than 
that.
The problem is, PC clocks (though called 'Real Time Clocks') can be quite 
bad, much worse than the cheapest wristwatch you can buy in a coffee-store. 
So setting the clock for an accuracy of 0.1 sec or better only lasts for a 
few MINUTES (!) on some nasty PCs (like the one I have to use sometimes). 
What really helps would be a GPS (costly, only works if satellites visible) 
or a cheap DCF receiver connected to the serial port (if not already occupied 
by mouse, modem, PIC, TRX control, DSP board etc etc).
You have to readjust the clock continously, if you want 'reliable' second 
markers for recording intervals of an hour or so. A possible workaround would 
be using the soundcards "calibrated" sample rate as a timebase.

I once implemented such "time marker lines" in Spectrum Lab (configurable 
from 1 sec per line to several minutes) but that feature seems to be hidden 
too deep in the configuration dialog hi. Anyway, you may try it to check how 
fast the PC clock 'runs away' from the DCF-signal observed with a fast 
scrolling waterfall (by the way, a nice experiment comparing the clock pulses 
from DCF and MSF).

Sorry abt my latest posting - it has a redundancy of exactly 100 percent !

73's Wolf.