A discussion on the differences came up somewhere not long ago. I had made
some measurements while re-doing the filter in my ATS-3 and also when using
the "short" crystals in another ("measurement receiver") project.
They (the short crystals) showed good Q in comparison with the HC-49/U
crystals and I didn't pay much attention to the relative Lm and Cm values
until I found some info from Wes Hayward saying that the reactances are
much larger in the short crystals.
Well yes, it was as plain as it could be that the short crystals had Lm
values three times as high as for standard height crystals on the same
frequency. Hayward said that the differences could make filter design with
these crystals more challenging.
I haven't looked at how it affects "pullability" of the crystals in a VXO
though.
73-
Nick, WA5BDU
Nick Kennedy