
Re: Surprise, surprise...
signals to/from spacecraft use microwave beams, as I understand it, a highly directional signal. Transmitters on setellites don't put out kilowatts of power as I understand it. You need about 3 or 4 times the radiated power to amplify it to that level, and that's a LOT of solar panels or fuel cell or nuclear power. One source says that Voyager has a 23 watt transmitter. Another source says that the current total power consumption is 249 watts for the entire spacecraft. Yet another source says that GPS satellite transmit at around 25 watts. In any case, it's not the kilowatts or megawatts you'd need to send an easily detectble signal out in an omnidirectional broadcast. [you make up for the low power by using high gain directional antennas, aka 'beams'].
But if you were _REALLY_ lucky, you might be listening within the cone of such a beam and so you might detect it. Might. And that's the point of SETI and others searching everywhere for many years. Various conditions may not allow us to receive signals for long enough so we just scan what we can. The earth has day/night periods and revolves around the sun, and you can't really listen well during the day on Earth, nor in the general direction of the sun with satellites. So there ya go. "When we can". Maybe do it enough times, you find something. [similar thinking in nuclear physics sometimes]