[time-nuts] Best Rubidium Frequency Standard
Bob Camp
kb8tq at n1k.org
Sun Mar 13 10:37:40 EDT 2016
Hi
> On Mar 13, 2016, at 4:37 AM, Iain Young <iain at g7iii.net> wrote:
>
> Hi,
>
> OK, so I'm about to show the limitations of my knowledge :)
>
> Bob Wrote:
>
> On 11/03/16 22:51, Bob Camp wrote:
>
>> If your target is something like a microwave radio, many Rb’s are
> > “challenged” in terms of phase noise and/or spurs. Some sort of
> > cleanup will be needed for almost all of them.
>
> Are some models particularly better than others at either phase noise
> or spurs ? If so, do we know which ones ? Or is it more a case by case
> basis (damage/maltreatment not with standing...) ?
Hi
None of them are what I would call “good” for phase noise or spurs. Even a cheap OCXO will beat them all. The “least awful” that is commonly available on surplus is the PRS-10.
>
> Also, are we "simply" talking LPF/HPF/BPF precautions here ?
No, not at all, the phase noise and spurs are all over the place.
> Or would
> folks advise doing other things as well ?
You need a good clean OCXO and a very narrowband clean up loop. How narrow depends on how good your radio needs to be.
> The microwave radio isn't
> going to care about delay through any filter [assuming that delay stays
> constant of course] (Different on the timing side of course)
You would need a filter with a 30 db bandwidth of < 1 Hz to even begin to clean up some of these.
>
> (I looked at the 10MHz output from the KS24361 boxes that Bob posted
> on here, with all the multiples, and brain simply screamed LPF.
That’s a *much* cleaner output than most of these Rb’s.
> Saw
> the sub harmonic, and it shouted HPF at me!)
Most microwave radio setups are going to ignore stuff like sub-harmonics. Their multiplier chains are plenty narrow enough to take them out.
Bob
>
>
> Iain
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