# What is the maximum isotropic radiation range achievable with my XBee-PRO?

Hi everyone ,

I have bought a XBee-PRO 802.15.4 RF, 2.4GHz Module, 63 mW, RP-SMA Connector. Moreover, I have been studying about the antenna gain. I was wondering what is the maximum range that I can achieve while maintaining an almost spherical radiation pattern (isotropic radiation) using this Xbee? How can I calculate the range of such sphere? How does the gain of antenna (not power gain) come into this?

I am not aware of there being a different formula for calculating range. As far as I am aware there is only the one.

I see. My understanding is that I can put a variety of antennas with the compatible RP-SMA interface on my Xbee, but each based on their gain (in terms of the pattern of reflecting the signal), provide me with a range. Nonetheless, if I use a high gain antenna I will get a sharp eliptical area of signal coverage (right?), while a low gain antenna will provide me with a more or less spherical area of signal reception. Now, I do not know that formula that you are referring to, but intuitively I think that if I were to use a low gain antenna to achieve a spherical range, whatever I get is the maximum range possible with my Xbee module and no antenna can increase the radius of that sphere without changing it into an ellipse. So am I correct that I need a higher powered module (not a higher gain antenna) to increase the radius of my sphere?

That is incorrect. Using a high gain antenna does not give you a sharp elliptical area. A directional antenna is what gives you an elliptical coverage area as apposes to a flattened doughnut shaped pattern created by a Omani directional high gain antenna.

That is not entirety correct. While increasing the output power would help, so to would a properly designed antenna such as 1/2 wave or 3/4 wave dipole or mono pole antenna.

I see. So I have a choice of a directinal antenna and an omni-directional antenna. In my case I just want to maximise the raduis of the sphere of my directional antenna or the outer radius of the doughnut of my omni-directional antenna. How can I figure out the maximum range of my sphere or doughnut considering the Xbee that I have?
Would you know if such an antenna (β1/2 wave or 3/4 wave dipole or mono pole antennaβ) exists that is also compatible with my Xbee RP-SMA ?

To maximize a radius, you would use an Omani directional antenna.

In general terms, for every 6db of gain you add in an RF LOS environment, you double your range. For Non LOS environments, you need 12db of additional gain to double your range.

All of our Dipole antennas are considered 1/4 Wave and have a gain of 2.1dB.

Thank you very much. I think I have a clearer idea of what I am after now.