[time-nuts] Auto-fail-over switch

[Mark Goldberg]

On Tue, Feb 5, 2019, 8:00 AM Bob kb8tq <kb8tq at n1k.org wrote:

> Regardless of how you do it, isolation is an issue. Having a 10 MHz
> standard line with a very
> close in spur is not a real good thing. It can mess up a lot of stuff and
> it passes through the
> cleanup loops in most gear. Is 120 db far enough down? I’ve certainly seen
> problems from
> stuff at that level at a small offset …. Simply having a switch with this
> or that db isolation is
> just a starting point. Grounding and shielding are very much on the “to
> do” list as well.
>

I was going to mention that. I modified my Perseus SDR to use an external
oscillator and just removing some SMT resistors to disconnect the original
oscillator output was insufficient. Still coupled in a spur from the
original oscillator and bad close in phase noise. I had to disable the
original oscillator by removing power. I didn't spend the time to try to do
that automatically. Maintaining phase continuity in the changeover would
also be hard.

Do you have any examples of something small that does this well?

Regards,

Mark


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