[time-nuts] Holdover: Z3801A vs KS-24361

Bob kb8tq kb8tq at n1k.org
Thu Apr 12 08:58:47 EDT 2018


Hi



> On Apr 12, 2018, at 1:30 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> On that Status page, A Z3801A says:
>  Predict  2.5 us/initial 24 hrs

That sounds about right for a 3801. The prediction is something better than
a wild guess and not what one would call a solid number.


> 
> A  KS-24361 says:
>  Predict  394.1 us/initial 24 hrs

That would suggest the unit is unlocked. It should be below 10 us. Just as with
the 3801, the estimate is a bit fuzzy. You should be able to see issues in the data
on the Z3809/Z3810.

 A prediction of < 1 can pop up on occasion, on either unit. More typical estimates
are in the “couple of us” range. If you yank the antenna, it still does a respectable 
~5 us / 24 hrs or so either way. 

> 
> Both have been running for weeks.
> 
> Is anybody seeing similar?

no

> 
> 
> Also, the Satellite Status area has a header of SS on the Z3801A and C/N on 
> the KS.  Does anybody know the units and/or what that is actually measuring?

There are tables that translate the Motorola (and some of the other brands) status 
numbers into rough dbc/ Hz. I would not count on the numbers on a 20+ year old
design lining up directly with the latest and greatest modern module. Apparently 
the SNR calculations are a bit weird.

Bob

> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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