The two types of cellular telephony radiation use different carrier frequencies and give different frequency spectra, but they usually also differ in intensity, as GSM 900 MHz antennas operate at about double the power output than the corresponding DCS 1800 MHz ones .
What is the main difference between GSM 900 and GSM 1800?
gsm 1800 channels Duplex spacing of 45 MHz is used. Guard bands 100 kHz wide are placed at either end of the range of frequencies. In some countries the GSM-900 band has been extended to cover a larger frequency range .