can u change the crystal in a phone to a lower one & it still work [i.E. cordless home phone ]?

Question

say from900 mz to 400 mz?

Answer 1

No. The crystal isn't the only thing that determines the frequency anymore. First of all, modern phones operate on more than one channel. In the case of 900MHz phones, they typically operate on 40 channels. To compound things even further, the transmit and receive frequencies are different from each other and the band usually dictates the spread that they operate on. A much lower frequency crystal is used in conjunction with a frequency multiplier in order to get the high frequency. You could replace the crystal and nudge those ranges up or down 10MHz or so, but any further would require retuning the circuitry. Anything as significant as a drop from 900 to 400MHz would require a complete redesign. The antennas aren't compatible, the RF circuitry definitely not compatible, and all that aside, anything in 400MHz is not set aside for use by cordless telephones and you'd likely be interfering with licenced users such as the police so even if you were successful, it'd be a good way to get yourself in trouble in a hurry!

Answer 2

now, why you wanna do that??????