Xbee Pro Series 1 with wire antenna range < 100 meters in open parking lot

I am using XBee Pro 60mW Wire Antenna - Series 1 (802.15.4) from Sparkfun for my robot ground vehicle.

The problem is that I am not getting range of even 100 meters using these modules in a open parking lot.

I have placed the xbee pro module at the top of the rover, ~30 cm above ground.
The other xbee pro module is connected to my laptop. The baud rate I am using is 38600. At close range I get all the data, but am having issues at range > 20 meters.

Is there a way to increase the range? I read through digi Application note about the fresnel zone. Can I replace the wire antenna by a longer cable, or a different type of antenna?

I really need this to work.
Thank you for your help,

You are going to need to get the antennas higher in the air. It is as simple as that.

In your case, you can’t change the antenna. You are going to need to order the RPSMA or U.FL versions of the product which do allow you to add external antennas.

Hello Rudraxx,

Are the wire whip antennae being bent in any way?
These wires are 1/4 wave antennae that use the XBee PCB as a ground plane to virtually create a 1/2 wave antenna. If the antenna is bent, then the effectiveness of the antenna is severely diminished.

Also, speaking of ground planes, what is directly below the XBee? If there are metal objects, then this could cause issues with the 1/4 wave “mirroring” that occurs with the XBee PCB plane.

On the ground vehicle module, is the antenna in open space, or is it enclosed? If so, what is the material of the enclosure?

Are both modules oriented in the same fashion? If one antenna (full module in this case) is 90 degrees out of phase from the other, you will automatically loss 12dB of signal. This is very significant.