moon

....... Phil

Yes. Radio HAMs do it to this day because, well, because that's the kind of thing they like to do. The US Navy developed a system in the 40s and

Tim

Ham radio operators have used it for long distance connection.

The US Signal Corp bounced radar signals off the moon in 1946. Other experiments followed. Some of the early satellites were actually passive reflectors, specifically intended for bouncing signals off of.

Amateur radio operators started doing it in 1953. I seem to recall that it took some time before that for actual success, ie some had been trying for a while before there was success. Unlike the US military, ham transmitters were limited to 1KW input, so they had to make up for that limited power through other means.

The signal is of course pretty weak by the time it returns to earth. You can offset that by using a stronger signal at the transmitter, and of course using large antennas, at the transmitter and at the receiver.

Sam Harris was one of the relatively early hams to do moonbounce. Then, he got a job at Arecibo, and moved there, which I gather caused him to give up on the field. But, a couple of times after he moved down there in '64, he arranged to use the Arecibo array for moonbounce a couple of times. With that size of antenna, it made it really easy for others with relatively simple equipment (ie not the most low noise receivers, not the maximum transmitting power, and relatively small antennas). It apparently sounded like quite a crowded band, listening on the Arecibo array.

One ham in Australia took it up, but there they were limited to a far lower power limit, the exact limit I can't remember. But he lived in the Outback, and had lots of room, so he used stacked Rhombic antennas made out of wire and surplus telephone poles. The size of the array made up for the lack of power. But, he couldn't direct the antenna, which limited the amount of time each month the antenna could "see" the moon. Eventually he rigged something so he could shift things a bit, and get more time in.

Fifty years ago, there were big issues with the lack of low noise amplifiers for the receivers. Tubes were all there were, and they were generally noisy. And the higher you operated, the fewer selection of suitable tubes.

That got better when the parametric amplifier came along, though they were in themselves complicated. When transistors got better, that helped a lot.

There was a whole period where various schemes were introduced for picking those weak signals out of the noise.

At this point in amateur radio signals, and the seems to be the main area that the concept is used (moonbounce had more potential before communcation satellites, but since they exist in large quantities, the need for moonbounce has diminished, and usually isn't worth the effort except to do it), there are apparently enough stations that have Big Antennas, good receivers and maximum power amplifiers that it allows for contact with relatively simple stations.

Michael

We all knew that when we saw your name in the "From:" column.

It's called EME.

yes

--For a good time search on "Mary Lou Jepson" who had an interesting idea concerning bouncing stuff off the moon, heh.

-- "Steamboat Ed" Haas : There's never a tachikoma Hacking the Trailing Edge! : around when I need one!

Earth-Venus radar has been done, too.

John