[time-nuts] 10 MHz 'failover' switch?

Hal Murray hmurray at megapathdsl.net
Thu Jul 26 18:05:17 EDT 2018


kb8tq at n1k.org said:
> One interesting subtlety making something like this:
> What if the two inputs aren’t quite on the same frequency?  Purely as an
> example, say they are 1 Hz off from each other.  If you have 60 db of
> isolation in your “switch” you get a 1 Hz offset spur that is 60 db down.
> Even something much further  down is plenty to mess up the ADEV of the
> output. 

Has anybody built a microprocessor controlled PLL to handle this case?  If you 
have the microprocessor and DAC, watching a second input and switching in 
software doesn't seem like a big step.

---------

Can I put two switches in series?  The is-it-working logic has to be look 
before the first switch, but the first switch is on-off rather than A-B.  It 
can be in a separate package placed to minimize feed-through.


-- 
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