[time-nuts] Aging 5065A ?

[Bob kb8tq]

Hi

It would be far easier to just use a (stock) 48 bit chip than to try to 
get something like that up and running ….. Keeping all the transitions
“just right” would be tough. If you don’t do that, you have a major added
source of spurs. 

Bob

> On Oct 8, 2020, at 10:14 AM, Lester Veenstra via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 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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