[time-nuts] Checking accuracy of Rubidium standards

Jeffrey Pawlan jpawlan at pawlan.com
Sat Nov 8 18:40:52 UTC 2008



On Sat, 8 Nov 2008, Randy wrote:

> I was wondering if it is worthwhile or even feasible to compare an LPRO
> Rubidium standard against a Z3801.  Since their frequencies are probably
> going to be extremely close anyway it would seem some special
> method/equipment would be required for high precision.  Suggestions?
>
>
> Randy, W7HR
> Port Orchard, WA

The best way would be to compare the highest possible frequencies you can 
generate with these two sources. I use two 10GHz sources that are each phase 
locked to an external 10MHz reference. Then the 10GHz outputs can be compared 
using either of these easy methods:
1) look at the DC/IF output of a microwave mixer where the LO and RF ports are 
driven by the two 10GHz sources. Don't overdrive the RF input to a level that 
can burn out your mixer.

2) use a good microwave frequency counter to read one of the 10GHz outputs while 
driving the counter's 10MHz ext ref input with the 10MHz from the other 10MHz 
source. This is very fast but will only give you accuracy readings that are a 
function of the resolution of the counter plus the bounce of the last digit 
owing to sampling and triggering.

3) if you have access to a lab with one or two microwave synthesized signal 
generators, then you can apply the 10MHz sources to the ext ref inputs of each 
of these signal generators and then proceed as in 1) or 2)
I have done comparison at 26GHz this way so I have a bit more resolution.

73,

Jeffrey Pawlan  WA6KBL




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