On the transmit side, the I and Q information at 0-2.5 MHz are first filtered from upper harmonics, up-converted in an I/Q up-converter mixer to an intermediate frequency, filtered again, up-converted to the final RF frequency (mixers can down-convert or up-convert), amplified to about 0.1-10 mW, filtered to remove any residual noise from the medium power amplifier, amplified again to 1-2 W (with 80 dB power control), and then sent to the diplexer. On its way, the power is sampled using a -20 dB coupler for the feedback loop in the power control circuitry. Again, the LO signal selects which channel to use in the 1920-1980 MHz band (maximum is 5 MHz band).