[time-nuts] Aging 5065A ?

[Lester Veenstra]

This I suspect is not original, but with respect for the need for 48 bit
resolution, why not, say, a 24 bit, with reduced range such that it's steps
are the same as what  you would see with 48 bits, this stacked (Biased) on a
fixed stable voltage in middle of expected control range. Fixed voltage
could be sourced from an initial courser wide range device.

Since this seems so obvious, who did it first?

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y
lester at veenstras.com

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-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at lists.febo.com] On Behalf Of Hal
Murray
Sent: Wednesday, October 07, 2020 6:18 PM
To: Discussion of precise time and frequency measurement
Cc: hmurray at megapathdsl.net
Subject: Re: [time-nuts] Aging 5065A ?


kb8tq at n1k.org said:
> If you want to run a fixed / well regulated C Field, a DDS with (say) 48
bits
> would allow you to tune the device well past  parts in 10^-15.

I don't know how to think about a DDS in this context.

I remember years ago thinking that a DDS was the greatest thing since sliced

bread.  In the context of something like a PPS going into a PC for 
timekeeping, that's probably true.  You get long term accuracy and the PC 
can't see the short term issues.

But then, somebody mentioned close-in spurs.  They get closer the more bits 
you have in the DDS magic number.  (What is that number called?)


Suppose I have a black box labeled "10 MHz" with a cable coming out.

If you plug that cable into your ADEV measuring setup, can you tell if my
box 
has a DDS in it?

If you plug that cable into your spectrum analyzer, how good a setup do you 
need in order to see the spurs?  Do they get lost in the close in noise?  Or

maybe the question should be how clean a signal do I need to start with
before 
the spurs become visible?  Or what should I be asking?


-- 
These are my opinions.  I hate spam.




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