I wanted to know more about the crystal fitlers used in the Tait Orca handhelds ie 45E12AA and 45E15AD.
I could not find the specifcations for these exact filters. However, after looking at some NDK datasheets I believe these crsytal filter are as follows:
45 - denotes the nominal center frequency
E - couldn't work the meaning out. Perhazps E means 2 poles and EE means 4 poles?
12/15 - bandwidth inkHz
A - finalises model number
A/D at the end denotes the center frequency.
So, 45E12AA apears to be a 45.1MHz 2 pole crystal filter (seaching for 45E12A did not return a model datasheet, perhaps a special Tait specification?)
and 45E15AD is a 45.1MHz 2 pole crystal filter (search for 45E15A to see the model datasheet)
Seems strange that the center frequency is not denoted by a consistent letter. But as expected when looking for relatively old datasheets, not everything is on the web.
Best to keep the crystal used to mix the IF down to 455kHz with the filters so you can derive the center frequency if no data can be found.