[time-nuts] Rb as source for ADEV?

Bob Camp lists at rtty.us
Fri Feb 7 13:11:11 UTC 2014


Hi

If you want one second ADEV (or something close to it) you need a beat note that’s above 1Hz. If one second is not of interest, then lower is fine. 

If you want to use a normal OCXO as the offset oscillator, you need to be inside it’s trim range (either high or low). That rules out anything much over 10 Hz at 10 MHz unless you have some unusual OCXO's. 

Most 10 MHz OCXO’s will tune a hertz or more off of 10 MHz. Digital Rb’s like the 5680 will make it a bit further if you pick which side you tune to. 

You are after another 3 or 4 digits ( ppb’s -> ppt’s) . 10 Hz might (but won’t) get you another 6 digits. Any offset you get by tuning a good OCXO will do what you need to do.

Yes there are other more complicated ways to do this. Yes they can get you to a lower floor. If you are looking at an Rb or most GPSDO’s, there’s no need for anything more complicated. 90% of it is audio and non-critical in terms of layout. 

If you did it on a real board and bought the parts in any sort of quantity, raw cost could be below $10 without the connectors. And before I get clobbered again, no I’m not trying to sell the boards. 

Bob

On Feb 6, 2014, at 9:47 PM, Hal Murray <hmurray at megapathdsl.net> wrote:

> 
> Bob Camp <lists at rtty.us>:
>> Offset the local reference one hertz or so and let the 5334 do it’s thing. 
> 
> Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz?
> 
> How did you pick 1 Hz?  Is 10 Hz offset better?  How about 0.1 Hz?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
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> 
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