 both meet initial customer needs and also provide a relatively low-cost method of meet- ing the Federal Communication Commission (FCC) regulatory requirements that a cel- lular provider must provide coverage to a certain percentage of the area and a certain percentage of the population covered by the provider's license. Later on, when we have more customers, we add smaller growth cells and convert the original cells into smaller growth cells as well. Having the antennas lower helps the base station serve nearby subscribers in its own cell and not interfere with more dis- tant subscribers in other cells. This means that the platforms on the original high tow- ers may need to be lowered. Each antenna has its own cable connecting the equipment on the ground to the an- tenna high up on the tower. Each cable has to have low enough electrical impedance not to have too much signal loss and has to be well enough shielded that it does not be- come an antenna itself and defeat the carefully engineered radiation pattern of a sec- torized cell. If the tower is 50 m high (165 ft), then this means 50 m of radio frequency (RF) cable for each antenna. The transmit antenna cables have to be able to handle the voltages and currents of the transmitter. Any receiving cable tens of meters long has a few decibels of loss. When a CDMA base station is serving a large-radius coverage cell, the tower is high, SO the cable is long, and the noise level of the receiver is a significant factor when compared with the weak signals coming from distant user terminals. When this happens, we can put a low noise amplifier (LNA) at the top of the tower and connect it directly to the antenna. This boosts the received signal, creating a higher signal-to-noise (S/N) ratio at the receiver at the bottom of the base-station tower. 4.3 The Power Amplifier Power amplifiers take low-level modulated radio signal and amplify it to sufficient power for an antenna to transmit it. There are many books on power amplifier design, both for audio frequencies and for 