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Tom Hutter has the distinction of being our first member to detect The SETI League's 1296 MHz moonbounce calibration beacon with a Project Argus radio telescope. Newly returned to service at the 150 watt level, the W2ETI beacon provides a stable, continuously available microwave signal, reflected off the surface of the Moon, to verify the proper operation of our receiving stations. Tom Hutter image

Something strange was noticed in viewing the above signal in the frequency domain: the spectrum analyzer image shows two distinct peaks. Since Hutter's Project Argus station is a scant dozen miles from the W2ETI Moonbounce Beacon's station location, we conclude that Tom is receiving the direct signal (via the beacon transmit antenna's sidelobes, into a sidelobe of his dish) and its reflections off the Moon, nearly simultaneously (differing in time only by the 2 1/2 second round-trip lunar propagation delay). Tom Hutter image

In its Doppler Display mode, the SETIFox software shows a rather unusual pattern. The hump to the right is due to the strong carrier from the direct signal, which is on a fixed frequency. The center vertical line is due to the weak signal (received via the EME path) which is slowly decreasing in frequency, due to the Doppler shift imposed primarily by the Earth's rotation. "Of course," notes SETIFox creator Daniel Fox, KF9ET, "the detection algorithm operates best with only one signal in the data." Tom Hutter image

Two days following the above observations, Hutter ran a series of frequency-domain images encompassing lunar zenith transit. In this first image, the direct signal is quite strong (in fact, it is offscale), while a weak reflection appears perhaps 100 Hz higher in frequency. The echo is blue-shifted, because just prior to zenith, the Moon is effectively moving toward the observer. Tom Hutter image

Just seconds later, the echo is red-shifted about 100 Hz. The moon has passed through the zenith position, and is now effectively moving away from the observer. Notice the very rapid change in frequency; the Doppler amount is minimum, but the Doppler rate maximum, right at meridian transit. Tom Hutter image

A few seconds after the above observation (that is, well after the Moon has transited zenith), the echo has moved still lower in frequency, while the strong direct signal (still offscale) remains stationary in the spectrum analyzer display. Tom Hutter image

SETIFox programmer Daniel Fox has done some post-processing of Tom Hutter's received signal. Here we see the beacon callsign ID in the time domain (oscilloscope view). The vertical axis represents signal amplitude, and the horizontal axis corresponds to time. KF9ET image

Here is the same post-processed signal, seen this time in the frequency domain (spectrum analyzer display). The horizontal axis represents frequency, and the vertical axis portrays signal amplitude. KF9ET image

Here again is the post-processed moonbounce signal, now viewed in a waterfall display. The horizontal axis represents time, the vertical axis is frequency, and the colors represent variations in amplitude. KF9ET image

This Spectra Plus frequency-domain screen very clearly shows the EME beacon, received via both the direct and the lunar reflective paths, at nearly equal amplitude. Tom Hutter image

Viewed in a waterfall display, the direct beacon signal shows up as a vertical line, while the EME echo is diagonal due to Doppler shift. Note that the ever-decreasing echo frequency starts off higher than the transmitted frequency, ends up lower, and that the two are exactly equal when the moon transits the receive station's zenith.. Tom Hutter image

Finally, click on the speaker icon at right to hear the audio .WAV file, as received at Project Argus station FN20ut, and filtered in the SETIFox software. Tom Hutter signal