[time-nuts] Near-perfect chip for Loran-C frequency receiver
phk at phk.freebsd.dk
Sat Jul 5 02:43:26 EDT 2008
In message <486EC7F0.10006 at xtra.co.nz>, Bruce Griffiths writes:
>Poul-Henning Kamp wrote:
>> Look at:
>Nonsense, although it may work in favourable cases where the signal
>levels arent too disparate, in the more general case this isnt true.
Bruce, you are input-resistant, please read what I write:
1. I am not trying to solve the general case.
2. I am quite happy for it to work only in "favourable cases", because
most people in the western hemisphere live close enough to a Loran-C
for it to be a "favourable case".
>Thats obviously fine for some Loran applications but you haven't
>demonstrated that its also true when attempting to simultaneously track
>another signal of interest that is relatively weak.
Yes I have, but you seem to refuse to read it:
>Thats only a 33 dB difference in signal level what happens when the
>signal strengths differ by 60, 80 dB?
Then we don't care to track them, because we will not be able to
derive a sensible frequency signal from them.
This is *not* an attempt to build a shiny complex, gold-plated contraption
that can drag out a signal from half-way around the world in Hi-Fi
quality, described as:
>In which case a dedicated ST32M103 for Loran and another for
>MSF/WWVB/JJYDCF77 etc is appropriate together with optimised analog
>front ends, bandpass filters, notch filters and orientation of the
>individual antennae to null strong interfering signals should cope with
>most problematic sites.
That's exactly all the stuff I'm trying to avoid.
What I'll build is an <EUR100 single-chip receiver that will
discipline an OCXO or Rb against the strongest Loran-C signal
... And make an excellent platform for experimenting with SDR
on other VLF time/frequency signals.
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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