[time-nuts] ok, newbie questions
Said Jackson
saidjack at aol.com
Sat Nov 27 18:22:03 UTC 2010
I was thinking to tap-off the Ocxo itself with a small buffer and bypass all of the internal stuff. Will report on that later..
Sent from my iPad
On Nov 27, 2010, at 9:22, "W2HX" <w2hx at w2hx.com> wrote:
> 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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