Q. What antenna options on the XBee radios will give me the best range?
A. If everything else in an RF system is equal, then the range will depend upon the antenna gain. A little bit of antenna background may be helpful.
Antennas are the radiating element in a radio frequency communication system and work by focusing the energy that is broadcast. There are several common types of antennas including 1/4 wave monopole antennas, 1/2 wave dipole antennas and various types of printed circuit board or patch and gain antennas. Generally speaking the gain and patch antennas tend to be the most expensive as they are designed for fixed outdoor installation, whereas the PCB, monopole and dipole antennas are designed with cost and portability in mind.
The XBee radio family is available with three separate antenna options. The modules are available with a PCB chip antenna, a 1/4 monopole integrated whip antenna, and a U.FL antenna connector that allows for connection to a dipole or other external antennas. The new XBee Series 2 radio is also available with an RPSMA connector for attaching dipole or external antennas. The integrated whip antenna and the chip antenna can work well with all applications, but they are especially useful in embedded applications. The radios do not have any issue radiating through plastic cases or housings, and so the antennas can be completely enclosed in those types of situations.
The U.FL connector is used in conjunction with an adapter cable that can allow connection to a dipole or gain antenna if the housing is metal or if that solution is more desirable mechanically. Of the XBee antenna options, the chip antenna has the lowest gain and therefore will get the lowest range. The integrated whip antenna has a gain of about 1.8 dBi and excluding any cable loss, a dipole antenna will have a gain of 2.1 dBi. In most situations, the integrated whip or a dipole attached directly to an RPSMA connector will give you the best performance and range. An application note with more XBee antenna information can be found at: