Hi Marek -
I don't know where you are in CZ. I'm on the boarder in DE near PL and
CZ. The distance to DCF77 is about 450km and if I check the amplitude
across 24h I see considerable very deep fading effects! I think it is
useless as a phase-coupled time receiver. At least in specific
positions. It will loose phase at least for twice the day for approx. 2h
! That was the report for a ferrite rod.
The other way would be a high-impedance FET-preamp vertical-wire
antenna. I think this will resist much more fading effects. But it is
unchecked at the moment. You're welcome to do it.
The benefit of a resonated ferrite rod is the good bandpass filtering
for local interferers like TV. The FET vertical wire will need heavily
filtering thereafter. All in the whole dynamice range, of course.
Ferrites can be temperature controlled. They have big spreads in
parameters anyway! The production procedure is explained in the
classical book about Ferrites: Snelling "Soft Ferrites".
- Henry
Marek Peca schrieb:
That would be 36ns group delay variation if I did the math correctly.
OK
And in article P. Hetzel: Time dissemination via the LF transmitter
DCF77 using a pseudo-random phase-shift keying of the carrier, 2nd EFTF
Neuchatel, 1988., they conclude with timing results of about 2..10e-6 s
RMS over ~1000km distance.
However, I do not know what is the reality and whether such a
performance is limited by atmosphere/ground conditions, or whether it
could be better within LF band.
However, what material are you using for the ferrite? The material can
have a significant tempco.
In my project, I have used noname rod taken from within DCF77 alarm clock.
If I will recreate it, I will look for something defined at the store.
--
ehydra.dyndns.info
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