In one example, a Bluetooth enabled navigation device pairs with a mobile phone and then sends a plurality of tuning transmissions, each at a different transmission power gain amount, to a remote server using the mobile phone. These tuning transmissions are encoded using frequency tones that synthesize speech for transmission through the mobile phone and a voice channel of its wireless telecommunications network. The navigation device then tunes transmit power settings according to a received response to the tuning transmissions and uses the tuned transmit power settings for subsequent transmission to the remote server using this particular mobile phone.