The Bluetooth* uses the same antennas used by your Wi-Fi. This is the reason you have a decrease in speed. Bluetooth wireless technology and Wi-Fi both use the 2.4 GHz ISM (Industrial, Scientific, Medical) unlicensed spectrum, and in some configurations can interfere with each other. It is recommended to turn off Bluetooth if not needed to have the antennas dedicated to Wi-Fi for better results.
Thanks for the response...that's too bad that's the way it functions. I feel like this should be pointed out in the product description because I was under the impression that I could use both simultaneously. Guess I'll use a USB Bluetooth dongle.