A single bay antenna provides the minimum needed to run a station. Most LPFM installations are single bay antennas.
A two-bay antenna does offer some better performance by focusing the signal more in an outward direction. Two bay antennas also have better performance over the single bay antennas and do not require as much power from the transmitter. For example, if you use a single bay antenna and are at 30 meters or less HAAT, you may have to operate 250 watts from the transmitter in order to make 100 watts at the antenna. With a two bay antenna, you may have to run about 110 watts to get 100 watts.
And while you may save a little money in the electric bill with a two bay antenna, you must take into consideration that a two-bay antenna will be more expensive to purchase (about $2,000 instead of less than $1,000 for a single bay) and if you are leasing tower space, you will be charged a higher rent for a two bay antenna because it takes more space on the tower.
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