[time-nuts] WWVB SDR discussion

[paul swed]

How do the small AM WWVB clocks work then. They use the 60 KHz crystal and
they don't actually do anything special. In measuring those clocks they are
about 2-6 hz wide. On the spectracoms the crystal is huge. Looks like a HC6
but 3" long. About 1-2 Hz wide.
Using the same small crystals in BPF filters does work and does not
seriously change within reasonable temperature. The one thing they do
is follow the crystal with a hi Z amplifier.
Just saying they work for all those atomic clocks for $10.
But back to the discussion here. Need some gain and filtering. There are
many good answers.
John night time is cheating. I get seriously crazy levels in Boston many
nights.
Enjoying the thread.
Regards
Paul.

On Tue, Aug 11, 2020 at 7:45 PM John Magliacane via time-nuts <
time-nuts at lists.febo.com> wrote:

>  On Tuesday, August 11, 2020, 07:14:12 PM EDT, Bob kb8tq <kb8tq at n1k.org>
> wrote:
>
> > The problem with the crystal is that it has a temperature coefficient.
> As a
> > narrow band filter, it will have a *lot* of delay. Crystal resonance
> moves
> > (with temperature) and the delay changes.
>
> I agree. The crystal needs to be ovenized. ;-)
>
> That very concern led me in my design to derive nearly all my receiver
> selectivity at baseband (DC) using op-amps, forgo any crystal filters, and
> keep the Q of the loop antenna low.
>
>
> 73.000 de John, KD2BD
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>