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LF: Re: re Xtal osc "delta emitter" tuning

To: [email protected]
Subject: LF: Re: re Xtal osc "delta emitter" tuning
From: "Vernall" <[email protected]>
Date: Thu, 10 Jun 2004 08:45:03 +1200
References: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Laurie G3AQC,

I'm pleased to hear that you have made use of the idea.  My original
objective was to be able to readily adjust the frequency of a calibration
grade oscillator, for which fractional ppm is adequate.  Your 0.5 Hz at 137
kHz is 3.6 ppm.

Since my earlier report I received a request to check the slope of the delta
emitter gradient, so that it could be used under automatic control in a
phased locked loop.  I checked a different design Colpitts crystal
oscillator to "double check" on gradient matters.  I confirmed that the
technique worked for fine tuning each, but the slope was "opposite".  So if
a particular oscillator is to be used in a PLL application, it needs to be
characterised for delta slope before designing the VCO drive.

Someone reading these postings may have a suggestion as to the semiconductor
mechanism(s) that bring about a variation in oscillator frequency.  It would
be unfortunate if some oscillator design had an S curve for frequency versus
emitter resistance.

73, Bob ZL2CA

----- Original Message -----
From: "Lawrence Mayhead" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 10, 2004 12:56 AM
Subject: LF: re Xtal osc "delta emitter" tuning

Thanks Bob for the sugestion, I have been looking for a means to pull the
oscillator that I use for QRS and DFCW.
The cap. in series with the xtal gives me coarse adjustment and now the
emitter resistance change enables a "fine tune".
I am able to achieve 0.5hz shift in the final 137 khz output. although I
need to reduce the emitter resistance by 50% to
achieve this.
73 Laurie.

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