I'm trying to read the ETSI standard regarding my 868MHz transmitter design.
I would like to transmit in one of the channelized bands ex. (868.600 to 868.700), which has a demand on 25KHz channel spacing. This sets a huge demand on the frequency error of the system. See table 5 of EN300 220-1.
A crystal of +/-10ppm would result in frequency error of +/- 8680Hz at 868MHz. So this does not leave much space in the channel for modulation of the carrier, and sets high demands on the modulation not spreading into the adjacent channels.
So, I was looking into high precision crystals, like +/-5ppm but these seems expensive, around 3USD which is more than my transmitter IC.
Does there exist any low cost, but high precision 10-12MHz oscillators that can be used for this purpose ?