Honestly.... I think I read somewhere the probe was operating at like 8 watts of power, and sent the pictures 3 billion miles. You know... I guess I’m wearing tin foil.... but something about that seems far fetched.
It takes 4 hours to receive a transmission from the probe.
http://www.businessinsider.com/why-it-takes-so-long-for-new-horizons-to-send-images-2015-7
Space is pretty empty, and it doesn't take much power to send a signal really, really far. Satellites receive the signal and use higher power transmitters to send it on to Earth. It's Earth's atmosphere which it harder to get 'through'.
why? You apparently don’t understand the nature of signal to noise ratios, background effects, or the ability of modern science
Average cell phones operate at .4375W. Less than a half of a watt.
It’s not using any propulsion at this point except maneuvering.
I know it’s more complicated than this before every one jumps on me, but the comparison is a digital camera, and radio transmitter. Remember the signal has no resistance in space.