I understand Diver300 The pull range has everything to do with the Q of the Crystal and 900 ppm off is not possible with Q of 10k or 1/100ppm.
There is a relationship between SRF and PRF in every crystal.
We often say SRF is Self Resonance Frequency as this is most common, but it should be called Series Resonant Frequency , SRF ( for all caps , series tuned crystals, dielectrics, insulators, or any material between two conductors, even a loop antenna)
Then we have Parallel Resonant Frequency, (PRF) ( for all inductors, par. tuned crystals, wires, antenna ) which is sometimes called-"anti-resonance" by resonator experts.
Crystal angles are cut by seconds which is 1/3600 of a degree and this affects the 3rd order shape of all AT cut crystals You can predict the SRF from PRF and visa-versa from the values below which also happens to control the Q of the resonator. Cpar is in pf, while Cser is in fentofards, fF
Typically SRF quality factors are specified by R values and PRF are defined by external C to get specified tolerance.
And that's why I think Mr AI's crystal was actually a SRF or series Xtal but tested as a PRF (Colpitts mode) which tends to have the offset he noted. ( but this is just a forensic guess)
There is a relationship between SRF and PRF in every crystal.
We often say SRF is Self Resonance Frequency as this is most common, but it should be called Series Resonant Frequency , SRF ( for all caps , series tuned crystals, dielectrics, insulators, or any material between two conductors, even a loop antenna)
Then we have Parallel Resonant Frequency, (PRF) ( for all inductors, par. tuned crystals, wires, antenna ) which is sometimes called-"anti-resonance" by resonator experts.
Crystal angles are cut by seconds which is 1/3600 of a degree and this affects the 3rd order shape of all AT cut crystals You can predict the SRF from PRF and visa-versa from the values below which also happens to control the Q of the resonator. Cpar is in pf, while Cser is in fentofards, fF
- Cser: 1~50 fF (femtofarad = 10^-15 F)
- L: 5~50 mH typ
- R: 10~100Ω typ
- Cpar: <10 pF typ
Typically SRF quality factors are specified by R values and PRF are defined by external C to get specified tolerance.
And that's why I think Mr AI's crystal was actually a SRF or series Xtal but tested as a PRF (Colpitts mode) which tends to have the offset he noted. ( but this is just a forensic guess)