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As a bit of curiosity, I was wondering what the longest path ever used by amateur radio operators has been.

Of course the opposite side of the Earth is no problem with a good HF station. And you can work long-path, so that's at least the circumference of the Earth.

EME contacts are an even longer path, even if the stations aren't as far apart.

A longer path would seem to require reflection off a natural satellite (doesn't seem feasible) or via an artificial satellite with amateur radio equipment. Have any of the few artificial satellites to have left Earth orbit had any amateur radio equipment? Or is there some other mechanism I'm not considering?

To be clear, receiving telemetry from any artificial satellite with amateur radio equipment does not count. I'm talking only about communications in the ham bands, intended to be used by the amateur radio service.

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  • $\begingroup$ This reminds me of the wonderful story that emerged recently of Larry Baysinger W4EJA of Louisville, Kentucky receiving and recording VHF signals directly from the Apollo 11 astronauts on the moon in July 1969, but those signals were not intended to be used by the amateur radio service. $\endgroup$
    – rclocher3
    Commented Apr 21, 2021 at 22:06
  • $\begingroup$ I wonder if a dual band "big gun" EME station has ever operated as a cross-band repeater between 2 other smaller EME stations. $\endgroup$
    – hotpaw2
    Commented Apr 21, 2021 at 22:56
  • $\begingroup$ Venus at closest approach is "only" 100 x as far away as the moon, so about 80 dB harder. Does a big EME station have an 80 dB margin? I have new respect for planetary radar. $\endgroup$
    – tomnexus
    Commented Apr 22, 2021 at 4:25
  • $\begingroup$ Correction - Venus is 67 dB weaker than the Moon because of the moon's much smaller RCS; $0.009\pi a^2$ at 3.6 cm, while Venus is $0.2\pi a^2$ $\endgroup$
    – tomnexus
    Commented Apr 22, 2021 at 13:11
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    $\begingroup$ Would you include those controversial Long Delay Echos (LDE)? One claim is that they're multi-orbits of the earth. Don't know if the timing of the echo supports a count of orbits. $\endgroup$
    – glen_geek
    Commented Apr 22, 2021 at 18:34

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AMSAT-DL has heard their own echoes on an Earth-Venus-Earth path, on the 13cm band, with the help of the 20-meter dish at Bochum Observatory. It falls a little short of "communication", but it seems that, given two stations with 20m dishes, a Venus-bounce QSO using QRSS, or perhaps one of the slow FSK modes (FST4?) would be achievable.

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  • $\begingroup$ I have no idea how much transmitter power they were using. If anyone is able to find that information, please fill it in :) $\endgroup$
    – hobbs - KC2G
    Commented Apr 22, 2021 at 5:24
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    $\begingroup$ Looks like 5 kW amsat-dl.org/en/… $\endgroup$
    – Phil Frost - W8II
    Commented Apr 22, 2021 at 15:40
  • $\begingroup$ Pretty sure 5 kW is outside what US amateurs, at least, are permitted to radiate. Maybe that 1500 W limit doesn't exist on one or more bands above 440 MHz? $\endgroup$
    – Zeiss Ikon
    Commented Feb 23, 2022 at 18:32
  • $\begingroup$ @ZeissIkon well yeah, but A) I didn't know that when I wrote the answer, B) it still seems like the best candidate, and C) I guess you could build your big dish in Somalia? They allow 3kW on all amateur bands. $\endgroup$
    – hobbs - KC2G
    Commented Feb 24, 2022 at 2:07
  • $\begingroup$ Or double the diameter of your dish -- only need another 6 dB gain. Of course, the neighbors might file a complaint before you can complete a 40 m dish... $\endgroup$
    – Zeiss Ikon
    Commented Feb 24, 2022 at 12:00

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