[OnlyMortal]

Firstly you need a target to send it to. Secondly you need to handle the rotation of the Earth so that you remain on target. Thirdly, you need to send a powerful enough signal that it can be detected above the background noise at that target.

The idea that aliens can pickup a radio station or TV station doesn’t seem likely to me. The rotation of the Earth would sweep that signal across them.

They might be able to detect “noise” at unusual frequencies but it wouldn’t appear coherent.

[signalioto]

If I just have a basic radiodish, send out a kilowatt of signal and keep it relatively stable, how far away someone could make it out though?

What if we as humans want to send a signal? Would we just detonate a bomb in space?

Couldn't it be possible that someone out there figured out how to travel tremendously fast but is just not able to find anyone?

[dredmorbius]

The Voyager probes transmit with a signal of about 23 watts, and are detectable (against a near-silent background) at a distance of about 0.002 light years (20 billion km):

<https://public.nrao.edu/ask/how-strong-is-the-signal-from-th...>

Signal attentuation follows the inverse-square law. A 1 kW signal is 43 times stronger than the Voyager's transmitter. It should reach about 6.6 times further.

So your 1 kW transmitter, if coming from a quiet noise floor (which the terrestrial environment is not) could reach at least 0.01 light years. Possibly further.

[OnlyMortal]

For detecting at a distance, it’d depend on the quality of your receiving system. The electronics in a radio make noise themselves.

A kilowatt won’t get far - the signal strength decreases over distance. I seem to recall CB radios with an amplifier could easily attain that.

No doubt someone here could calculate the theoretical wattage needed to appear above the background noise on, say, Proxima Centauri.

[signalioto]

Does it decrease due to the wave getting bigger or due to background noise getting louder?

Then a laser is a better choice?

[flangola7]

> Couldn't it be possible that someone out there figured out how to travel tremendously fast but is just not able to find anyone?

I find this doubtful because they could travel outward in a sphere, touching every celestial object in the universe as they go.

[signalioto]

They still could have some lifetime limitations.

Like only one flight per month.

Or they know how to do a very fast straight line but nothing local. Therefore needing to recharge and shot themselfs one waypoint after the next.