Paul,
In one of you earlier posts on this thread, you mention that you use a 20ppm crystal, can you share your source for this crystal. All the crystals I have found have a 50ppm tolerance at 25 deg and then a another 50ppm over temperature or then a worst case frequency tolerance of 100ppm, I would like to stay away from using a TXCO and 20ppm would be the right amount of acceptable tolerance for my project.
thanks,
Terry