[time-nuts] Homebrew WWVB TX simulator?

Magnus Danielson magnus at rubidium.dyndns.org
Tue Sep 14 21:32:48 UTC 2010


On 09/14/2010 11:10 PM, Bob Clements wrote:
>
> Has anyone built / seen / bought a small simulator for WWVB?
>
> I live near Boston, and the WWVB signal is pretty marginal around
> here.  MSF on the same frequency isn't that far away, and local
> noise is pretty fierce.  So now and then one of my WWVB listeners
> (like my generally nice Junghans wristwatch) gets screwed up.
> The firmware writers aren't very cautious, and there's no parity
> bit in the code.
>
> So I have the itch to build a micro-power WWVB to set stuff with,
> without having to wait overnight for one or more nights.
>
> Before I dive into such a project, has anyone done/seen such
> a thing that I could buy or copy?
>
> I've got a WWV/WWVH simulator that I wrote (and announced) back
> when they were about to replace the Audichron drum machines, and
> I can start from there if necessary.  The hardware part seems
> a bit more interesting, but for this purpose I don't need to
> derive the carrier from a GPSDO or my ancient Rb oscilator.

If you don't need a precision carrier, but rather a signal good enough 
for rough testing then you should not need to do that much other than 
cooking up a 60 kHz sine oscillator (maybe a simple cos/sin oscillator 
on op-amps will suffice) and let either a CMOS switch (4066) do the 
AM-modulation by shorting a resistor or enabling an additional 
resistor-path into a summing op-amp. Should not consume that many parts. 
Maybe add some damping stages such that levels can be controlled.
Maybe a PIC to do the modulations trains and a serial interface to set 
it up. In all about 3-4 chips. Should not be too hard.

Cheers,
Magnus




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