The external antenna provides 2.1dBi of gain at VHF frequencies and 4.5dBi at UHF frequencies. A 3dBi antenna gain is roughly equivalent to doubling the transmitter output power. The received signal strength and therefore the range can be increased by either increasing the transmitter output power or using a higher gain antenna. In this case, we use a higher gain antenna to increase the received signal strength.
Physically, the antenna has an upper section that is 17.25” long and a lower section that is 9” long. These sections are attached together and inserted into an antenna base with a 3.5” diameter. With the height of the base at 1.5”, total height of the external antenna is 27.75”. To allow some flexibility in positioning the antenna, the cable connecting the antenna to the BNC connector on the Charger is 1 meter or 39.4” in length.
