[time-nuts] Near-perfect chip for Loran-C frequency receiver

[Poul-Henning Kamp]

In message <486F2166.4080907 at xtra.co.nz>, Bruce Griffiths writes:
>Poul-Henning Kamp wrote:

>> 	http://phk.freebsd.dk/loran-c/CW/
>>   
>That is restricted to the Loran-C case only.

You have not actually looked at that page have you ?

Hint: "CW" is, as usually, used as an abbreviation for "Continous Wave".


>>> 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.
>>   
>So how come NIST at WWVH in Hawaii still manges to do this then?

I am happy tell you that NIST has taken great care to NOT inform
me, that they want to replace their very expensive high-end gear
with my <EUR100 gadget.

Likewise, I can inform you that I have neither the budget or level
of ambition of NIST in this area, wherefore a <EUR100 receiver that
will track a couple of loud loran-C signals is plenty to make me
happy.

>In the case of LF transmissions you would have us believe that anyone 
>beyond 500km (theoretical limit within which the DCF77 ground wave 
>dominates according to the PTB- excludes Denmark) from the DCF77 
>transmitter hasnt any hope of usefully accurate (1E-9 or better) 
>frequency comparisons against the received signal.

I can get 1e-12 from DCF77, as long as I integrate for about a day.

I can get 1e-14 from DCF77, as long as I integrate for about a year.

Please don't argue any more until you understand that.

>If the system is split appropriately into 2 modules the analog front end 
>and the DSP backend, customisation to suit a particular site is easy to do,

If you had read what I wrote originally, you would have realized instantly
that it is perfectly possible to use as complex an analog frontend as
you want.

The goal of my project is to use as simple a frontend as possible,
and there is nothing you can say to persuade me to make it more
complex than it needs to be.

Poul-Henning


-- 
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.