[time-nuts] Auto-fail-over switch

[Bob kb8tq]

Hi


> On Feb 5, 2019, at 11:59 AM, Mark Goldberg <marklgoldberg at gmail.com> wrote:
> 
> 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?

Nothing that I have seen on the surplus market. Some of the things companies I’ve worked for over the
years did a pretty good job ( at least to the specs the customer requested …). 

Bob

> 
> Regards,
> 
> Mark
> 
> 
>> 
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