Frequency offset error in receiver

I have a radio transmitting at 903.5 MHz and a receiver with a PLL fixed at that frequency. When i observe the signal after the mixer I see a frequency offset of 3.75KHz. What parameters of the PLL should I optimize to remove this offset?

the crystal reference clock is a little off in frequency. You need to buy a crystal with more accurate frequency accuracy, less crystal aging, or possibly control the voltage droop to the crystal.

The frequency is only off by 4ppm. Unless you have bought a good TCXO for your frequency reference that is to be expected, as biff said.

Keith.