Amateur station hears MRO at 45 million miles

This week the Mars-Net e-mail list reported that Paul Marsh, an amateur observer, has detected Mars Reconnaissance Orbiter at X band at a range of 45 million miles from Earth.

The MRO transmits on Deep Space Network channel 32 which is 8439.444444 MHz.
By the time that reaches Earth, due to doppler the frequency has dropped to around 8439.031 MHz. The MRO has a 3 meter diameter dish antenna driven by a 100 Watt X-band TWTA to transmit signals to Earth. The signal coming in our direction is of the order of 4.2 mega watts of RF.

The signal was clearly visible in the FFT display of an SDR-14 software radio, and was just audible in SSB bandwidth of a communications receiver. The signal was consistently about 6 to 8 dB above the noise floor.
More details can seen at:
http://www.uhf-satcom.com/mro/.

Thanks to Joe, KM1P, the Mars-net list, and
Uhf-satcom.com for the above information