Many radio owners are afraid to buy an FM antenna that has a negative gain. They think they will be losing half the output power.

The gain of an antenna is only measured in one polarization plane, not both. This means that the gain is only measured in either the vertical or horizontal plane. Circular and Cross antennas are circularly polarized antennas so there are both vertical and horizontal elements on them, consequently, there are both vertical and horizontal components to the signal radiating from them.

In a true circular polarization, half of your signal is in the vertical plane while the other half is in the horizontal plane. This means that, 50% of your output power is in the vertical plane and the remaining 50% in the horizontal plane. You don't lose anything; all of the 100% output power is still there.

Note that any gain figure of any antenna does not have any magic effect that can either amplify or destroy your RF power. It's simply a matter of how the power is distributed or radiated from the antenna.

When an antenna has a positive gain of +3dB, your power is not really doubled. Rather the antenna is simply re-distributing power from one area and placing it in another giving the illusion of increased power.

With negative or positive gain, no power is lost or no extra power is created. Rather the exact same amount of power is coming off of the antenna, but being distributed differently.

Listeners' receiving antenna can come in all shapes and sizes (vertical and/or horizontal types). When you are broadcasting on the FM band, it is best to send your signal using an antenna that has the same format or polarization as the listener's receiving antenna.

Since receiving antennas are available in vertical like a stick antenna on older automobiles or horizontal like the 300-ohm twin-lead antennas on most home stereo systems and/or window antennas on vehicles, it is best to transmit in circular polarization; both horizontal and vertical polarization. With the circular polarization, the station has both bases covered when it comes to matching up its transmitted signal with that of its listeners.

Since antenna gain is measured in one plane; vertical or horizontal, you are able to actually put twice as much power into a circular antenna than you can put into a vertical only antenna. By putting twice the power into the antenna, you are effectively putting twice the power into the air, which gives your station a better coverage than any "vertical only" antenna could ever provide.