[time-nuts] State of the art of crystal oscillator measurements
KA2WEU at aol.com
KA2WEU at aol.com
Thu Aug 11 19:10:21 EDT 2016
Values of kT at 25°C (298 K) Units kT = 4.11×10−21 _J_
(https://en.wikipedia.org/wiki/Joule) kT = 4.114 pN⋅nm kT = 9.83×10−22 _cal_
(https://en.wikipedia.org/wiki/Calorie) kT = 25.7 _meV_
(https://en.wikipedia.org/wiki/Electron-volt) Related quantities kT/hc = 200 cm-1 kT/e = 25.7 _mV_
(https://en.wikipedia.org/wiki/Volt) RT = kT ⋅ _NA_
(https://en.wikipedia.org/wiki/Avogadro's_number) = 2.479 _kJ⋅mol-1_
(https://en.wikipedia.org/wiki/Joule_per_mole) u = 0.593 _kcal⋅mol−1_
(https://en.wikipedia.org/wiki/Kilocalorie_per_mole) _h_ (https://en.wikipedia.org/wiki/Planck_constant)
/kT = 0.16 _ps_ (https://en.wikipedia.org/wiki/Picosecond)
In a message dated 8/11/2016 7:02:13 P.M. Eastern Daylight Time,
john at miles.io writes:
Right, I'm speaking specifically of L(f). The device being driven by the
oscillator doesn't care about the NF of the driver stage, only what a PN
analyzer would measure at the output jack.
For any 50-ohm source, the practical L(f) floor is -177 dBm/Hz - the
carrier power in dBm. No oscillator with an output of 0 dBm can be quieter than
-177 dBc/Hz at any offset, but an oscillator that puts out +20 dBm could
approach -197 dBc/Hz.
Given a proverbial black box containing a +17 dBm oscillator that measures
-195 dBc/Hz at 100 kHz, the interesting question is, "What's in the box?"
There could be a passive resonator that's shaving off the broadband noise
after the last active stage without contributing additive noise of its own.
Another possibility might be cross-spectral collapse due to correlated
thermal noise from the splitter.
-- john, KE5FX
Miles Design LLC
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of KA2WEU--
> - via time-nuts
> Sent: Thursday, August 11, 2016 2:37 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] State of the art of crystal oscillator
> NO, the maximum possible noise dynamic range is ( 177 + Pout) [dBm]
> Transistor large signal NF ( dB),
> the signal to noise ration is dimensionless !!!!
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