This one is completely about PCB layout. I have two 26MHz crystals in the design, one for each processor on the board (TXC
7M-26.000MEEQ-T, datasheet: http://www.txccrystal.com/images/pdf/number-crystal-accuracy.pdf). The processors are placed in opposite sides of the board, relatively on the same place, so that they are quite "back-to-back". The PCB is 4 layer FR4.
One of the processors is an RF-chip, while the other one is just an 32-bit MCU.
My question is; Is it good practice to place the crystals "on top of each other", on the opposite sides of the PCB? There is ground plane between the crystals, but I'm thinking if there could be some interference between the crystals..