XBee Series 2 strange Range Test Result

Hi,

I have to XBees Series 2 modules with chip antenna (http://www.sparkfun.com/commerce/produc … ts_id=8691). One configured as Coordinator, another one - as the Router. Coordinator plugged into the XBee Explorer Regulated (http://www.sparkfun.com/commerce/produc … ts_id=9132) and Din is connected to Dout to facilitate range test; the Router plugged into the XBee Explorer USB (http://www.sparkfun.com/commerce/produc … ts_id=8687). Both devices are sitting on my desk about 6 inches from each other and both are configured to operate at 115200 bod.

When I perform Range Test with the RSSI checkbox checked on the X-CTU interface (please see the screen shot) - everything works fne. However if I perform the same test with the checkbox un-checked, I receive about 50% errors (please see second screenshot).

As far as I understood manual, the checkbox just controls whether the signal strength is reported - why does it affect data transmission?

Thank you,

–Alex