[time-nuts] xtal oscillator phase noise

Mike Feher mfeher at eozinc.com
Tue Jan 1 07:42:11 EST 2008

Henk -

Did you try to measure the PN out of the oscillator directly without the
buffer amp (U1)? Also, what is the voltage from V1? Is it also 12V? HNY -

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Henk ten Pierick
Sent: Tuesday, January 01, 2008 7:25 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] xtal oscillator phase noise

On Dec 30, 2007, at 3:42, Bruce Griffiths wrote:

> Henk
> The 30dB/decade phase noise slope could be the result of the effect of
> low pass filtering a power supply or reference source that has
> significant flicker noise.

The reference used is an ADR455. I have not seen references  
significant better. Suggestions?

> Lack of local RF feedback and /or high dc gain from base to  
> collector in
> BJT buffer stages can produce significant flicker phase noise.

I have now doubled the dc voltage for the oscillating transistor for  
the reduction of junction capacitances. It had no result on phase noise.

Is low hfe better for phase noise?


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