[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[Bob kb8tq]

Hi

Since this is Time Nuts … crazy isn’t always ruled out :)

> ……….
> “TSP #162   Tutorial   on   Theory,   Characterization  & Measurement
> Techniques of Phase Noise"
> 
>  https://www.youtube.com/watch?v=SOHjFtw0sgo
> 
> each 5db  of improvement requires an order of magnitude  increase in
> the number of correlations.
> 
> dB      5       10      15      20      25      30      35      40
> N       10      100     1000    1E4     1E5     1E6     1e7     1e8
> 
> So going from -180dBc/Hz to 220dBc/Hz would require 1e8 correlations.
> 
> 6. Nobody would wait that long. But how many correlations do you need?
> ……..

Say you did go the brute force approach. We’re talking far removed
phase noise for stuff like -220 dbc/Hz so each sample set could be pretty short. 
Just to toss out a number, let’s go with 1 ms. Yes, this would be quite far 
from carrier.

We now are at 1x10^5 seconds of data. That’s “only” a bit over a day. That’s not 
an insane run time for an R&D environment. An “over the weekend” run of 
three days would get you all the way out to 3 ms sample sets. 

Want longer samples? 

How many samplers / correlation processors do you have? How much 
does each one add to the mix? If it was linear, you are out to a whopping
300 ms with “only” 100 processors. Yes that sounds insane. This isn’t quite
as simple as a video graphics card or four being plugged into a PC. Still, 
it could cut down the time. 

So maybe not quite so crazy after all …..

Bob