[time-nuts] wtd: WWVB info
Graham / KE9H
ke9h.graham at gmail.com
Wed Aug 5 13:40:10 EDT 2015
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
is 20 to 25 dB, so noise floor well below the atmospheric noise level at 60
kHz. You would only need a preamp if you were running some negative gain
antenna. Lots of dynamic range. Won't overload until 2 Volts peak-to-peak
or so. A very simple, high performance digital receiver front-end.
--- Graham / KE9H
On Wed, Aug 5, 2015 at 6:15 AM, Bob Camp <kb8tq at n1k.org> wrote:
> The front end would be “dealers choice”. He who does the
> project gets to decide what gets used.
> If you look over some other designs, you can indeed get
> a device going with a 12 bit converter. The qualifier is that
> the signal to noise needs to be pretty good. With fades
> and switcher interference, you probably would notice its
> The “other end” of the design spectrum would be with a part
> designed as a high range font end chip. You can get to a lot
> of bits at low frequency. Even the prices aren’t all that crazy.
> Is there one and only one approach here? Not in any way. There
> are several thousand possible ways to do it. AGC or no AGC would
> be a pretty major decision. Next decision would be things like clocks.
> 15 MHz from a ($25) KS box that also puts out 10 MHz looks like a
> pretty good choice at the moment.
> Past that it’s decimators / filters and the usual DSP stuff (or any of
> a dozen alternatives). Given the high noise environment I’d lean towards
> a DSP approach.
> Most of the choices run into the easy / quick / cheap tradeoff triangle.
> sure that the debating process can find a solution that should “cost 10
> cents”. I’m
> also sure that a basement lash up of available parts is quick, but hard to
> I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit
> that there are no unique lash up designs. The debate process seems to
> have made this a pretty un-attractive thing to do.
> > On Aug 4, 2015, at 11:36 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> > kb8tq at n1k.org said:
> >> So far there have not been any home brew design radios show up that will
> >> demodulate and lock to the new data format. There is plenty of info on
> >> transmit format. The demodulation approach is not crazy hard. That said,
> >> there’s still a lot of work to get a receiver running.
> > Has anybody looked into a software approach? What sort of front end
> > you want?
> > --
> > These are my opinions. I hate spam.
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