[time-nuts] Auto-fail-over switch

[Bob kb8tq]

Hi

The thing you will (rarely) find out there are devices that act like a GPSDO only the input is
10 MHz, or 1 pps or something else entirely (T1 , E1 …). They watch a set of inputs and 
(based on a list of rules) decide what is the best source to use. The output 10 MHz gets
locked to that until something better comes along or it goes away. 

If all your “stuff” needs a continuous 10 MHz, this is the sort of box you would want to have. 
It keeps your radio on the air, your frequency counter counting, and all those breadboards 
doing whatever it is they do. 

Since they aren’t real common, finding one is a bit of a chore. Finding one with inputs 
(and outputs) that are useful to you is a bit harder still. Figuring out the programming interface
to set up rules that make sense to you ….usually not very easy at all. 

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. 

Lots of fun !!!

Bob

> On Feb 4, 2019, at 9:26 PM, Jeff Blaine <KeepWalking188 at ac0c.com> wrote:
> 
> Wondered if anyone had seen some sort of gadget that would look to see if there was a 10 Mhz signal and switch a relay (or provide some other output) in the absence?  I would like to cook up some sort of fail over switch without having to do much actual work. :)
> 
> 73/jeff/ac0c
> alpha-charlie-zero-charlie
> www.ac0c.com
> 
> 
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