value of Analog pin of Xbee changes randomly!!!

Hi there

What I am trying to do it pretty simple. I am sending an analog voltage out of PWM of Arduino and I pass it through a LP filter. The output of the LPF gives me a relatively smooth average voltage. When I send this voltage to the A/D of xbee, the value keeps alternating between random voltages. I have defined the sampling rate and the IC on the Xbee. As soon as I connect the A/D pin to the output of the filter, the value keeps alternating.

Any help would be appreciated. Thanks.

Which XBee modules are you using and what are you doing with the VREF of the XBee module?