[ntp:questions] Re: radioclk DCF doubling

Jonathan Buzzard jonathan at uk.me.buzzard
Mon Jul 18 22:23:25 UTC 2005


On Mon, 18 Jul 2005 22:54:41 +0100, David Woolley wrote:

> In article <slrnddnari.jkr.serge.bets at laposte.net>,
> Serge Bets <serge.bets at NOSPAM.laposte.invalid> wrote:
> 
>> Sorry again I feel I don't understand. Do you mean the unfair duration
>> of low amplitude pulse being only 10% of a period, while high amplitude
>> is 90%, makes the filter detect faster one edge than the other?
> 
> That might be a contributory factor (by making it more difficult to
> calculate the correct slicing level), but what I really mean is that the
> edges are really slopes (actually curves) and if, say, the decision 
> voltage is less than halfway between the high and low voltage levels,
> a transition from low to high will be detected early and one from 
> high to low will be detected late.

The thing is even if the filter in the module has the decision level
at the mid point, the serial port *IS* asymmetric. It is swinging between
about 10~12V and 0V with the change over point at about ~1.5V.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195




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