Lets say there is a Von Neumann probe sitting on; or buried in the moon. All it has to do is send out a radio beep from time to time. Maybe we should point our radio telescopes at the moon. Finding a signal might be easier than we suppose. Perhaps a nano probe is a mere 10 miles above us; in orbit around the Earth? Why can't it just be beeping away?

Could what be this easy?

A ten-mile orbit Around Earth would not last very long at all, due to atmospheric drag, no matter what size your probe is. And itty-bitty machines would put out itty-bitty radio signals, which would get lost in the general RF chaos. What would be the power source?

Fred

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"For shame, gentlemen, pack your evidence a little better against another time."
-- John Dryden, "The Vindication of The Duke of Guise" 1684

A mere 75 watt transmitter is all that is required to reach any satellite dish on the Earth from low Earth orbit. IF there is any alien device on the Moon; it could make its presence known easily. Or perhaps the device on on another moon of our solar system. Maybe its located in the Oort cloud; ..we should be looking "locally"....

That was the premise of a short story called "The Sentinel".

It was published in >>> 1951 <<< and was the genesis of the movie "2001: A Space Odyssey" (1968) by Arthur C. Clarke.

So it's been thought of....

A probe here would be sending signals back to its home star, so instead of watching likely stars for signals we should send spacecraft toward those stars and have them look back for signals from here.

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Life is like a box of chocolates. All of your choices are bad for you.

I like to invoke Clarke's 3rd Law and say "any sufficiently advanced technology will be indistinguishable from magic" and suggest that unless we know how to detect magic, the possibility of picking up signals from ETi tech is vanishingly low.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Now that we know that sufficiently advanced technology is indistinguishable from magic, nothing will look like magic.

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Life is like a box of chocolates. All of your choices are bad for you.

I suppose it could. I guess then that the fact that it hasn't proves that there is no such device on the Moon.

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009
All moderation in purple

First, most of those dishes wouldn't pick up a 75 watt broadcast. Satellite TV and such use directional transmissions that target specific portions of the planet.

Second, 75 watts over thousands or millions of years is a lot of energy, and a continuous transmitter is likely to wear out and require replacement many times over. A better approach might be for the probes to to build resonant chambers ringing to the sun's radio emissions, dust planetoids to give them unnatural spectra (the spectral signature of titanium dioxide paint is how the "asteroid" J002E3 was eventually identified as the Apollo 12 Saturn IVB stage), etc, and spend most of the time dormant, waking periodically for repairs or replacement of lost probes.

The Oort cloud is a big place to put something intended to be found, and the planets and moons experience weather and impacts that could destroy or bury probes at a great distance from the actual impact. In free orbit, it would take a direct hit to take a probe out of commission. I've suggested the trojan points might be good places to look...orbits that are stable over very long periods, and points likely to be of interest to any emerging civilization.