[time-nuts] Stepping up the output of an OCXO
Ulrich Bangert
df6jb at ulrich-bangert.de
Sun Feb 4 10:47:09 UTC 2007
Bruce,
I have seen this specs before but do you know how to find the
schematics?
Best regards
Ulric Bangert
> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Dr Bruce Griffiths
> Gesendet: Sonntag, 4. Februar 2007 08:32
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Stepping up the output of an OCXO
>
>
> John Ackermann N8UR wrote:
> > I had a chance to measure a TADD-1 using an HP-3048 phase
> noise system
> > last year. I've attached a screen shot of the results; in short it
> > was below -140dBc/Hz from 100 Hz on out (by the way, I'm not sure I
> > would trust the noise floor shown in this test; I am not certain we
> > had the best test set-up). That's within a few dB of what HP said
> > their 5087A amplifier would do.
> >
> > I'll soon have access to a new phase noise measurement
> system and will
> > relook at the TADD-1 performance with it.
> >
> > John
> >
> >
> John
>
> My calculations using the component values in the circuit
> indicate that
> the TADD-1 noise figure should be about 19dB and its
> corresponding phase
> noise floor should be lower than -160dBc/Hz. when the input signal is
> +7dBm or greater. So unless you had an unusually noisy set of opamps
> and/or resistors the measurement setup phase noise floor probably
> exceeds that of the TADD-1 by around 20dB.
>
> With a 10V supply instead of 9V and a +13dBm input the phase
> noise floor
> should be about -168dBc/Hz which is respectable but a few
> (~10) dB shy
> of the state of the art.
>
> The only way to achieve the state of the art performance with opamps
> using a 9 or 10V supply is to use lower noise (2nV/rtHz appears
> feasible) opamps pairs driven in push pull by an input step up (1:2
> turns ratio) transformer with an output stepdown transformer
> driven in
> pushpull by the 2 opamp outputs. The noisy 1K input
> protection resistor
> would also have to be reduced in value as would the opamp feedback
> network resistors.
>
> NIST's 1995 distribution amplifier claims a phase tempco of
> 0.3ps/K and
> 120dB isolation between channels.
> http://www.physics.nist.gov/News/Update/950626> .html
>
> Bruce
>
>
>
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com
> https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts
>
More information about the Time-nuts_lists.febo.com
mailing list