[time-nuts] ok, newbie questions

W2HX w2hx at w2hx.com
Sat Nov 27 17:22:00 UTC 2010


I wonder if the 19.6608 isn't needed, if one could unsolder the logic
divider chips and reduce noise?

73 Eugene W2HX


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bruce Griffiths
Sent: Saturday, November 27, 2010 12:44 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] ok, newbie questions

Those switch mode regulator modules under the finned heatsinks in the 
Z3815A are likely responsible for most of the spurs.
The ECL/CML logic dividers and the various ouputs like 19.6608MHz also 
contribute.

Since the E1938A output is only +4dBm, its very easy to degrade the 
phase noise in the buffer chain if one isnt careful.
With careful design a discrete buffer amp phase noise floor below 
-170dBc/Hz should be possible with a + 4dBm input.

Bruce

SAIDJACK at aol.com wrote:
> Not necessarily so..
>
> My HP Z3815A here (desktop unit) has horrible phase noise and massive
> spurs. Really to cry over since I know what the internal OCXO (1938A type)
is
> capable of generating.
>
> See the attached plot.
>
> bye,
> Said
>
>
> In a message dated 11/26/2010 16:37:26 Pacific Standard Time,
> GandalfG8 at aol.com writes:
>
> So if I  want a really souped-up freq standard for my lab,  then I  should
> concentrate on finding the best oxco I can (which may be   disciplined by
> the
> GPS or manually occasionally calibrated to GPS), and  use  the best power
> supply I can find.  These seem to be what I  should  concentrate on rather
> than more channels.
>
> I do believe  that I read  some stuff on the internet that the HP GPS DO's
> do
> seem  to have very good  power supplies (or converters) which contribute
to
> low spurs. So it seems  the HP's do have a real advantage (not  just  the
> name).
>
>
>    
>
>
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