ET is listening to our broadcasts?

[neilzero]

Decoding = demodulating digital audio, PPM = pulse position modulation, FM/FM or spread spectrum is very complicated, but easy with the correct LSI = large scale integration chip.
If I remember correctly, there are 4 methods of decoding FM = frequency modulation: ratio detector, slope detection, quadrature something and I forgot.
AM amplitude modulation, a 1N34 diode. Single side band, same as AM except you have to reinsert the carrier frequency before detection with the 1N34 or one of several other methods. My guess is even very advanced ET = extraterestials can't decode some of our transmissions, and we can't decode ET transmissions without the correct LSI which are only manufactured on ET's home world. Reverse engineering is futile. ET likely has some modulation methods, we have never dreamed of. I'm sure my list above is seriously incomplete. Neil

[Jeff Root]

I would bet that any signal strong enough to be recognized as a
signal would have its encoding figured out in less than 24 hours,
even with no clue as to what kind of data it contained.

-- Jeff, in Minneapolis

[Luckmeister]

Digital transmissions began to be applied to broadcasting in the late 1990s, so unless ET is closer than about 11ly away, there won't be any digital decoding required. Also I believe it's questionable that our transmissions would have been powerful enough for them to detect at that distance.

[Noclevername]

Digital transmissions began to be applied to broadcasting in the late 1990s, so unless ET is closer than about 11ly away, there won't be any digital decoding required. Also I believe it's questionable that our transmissions would have been powerful enough for them to detect at that distance.

I think the latest studies showed that 1.5 LY is the distance where noise overwhelms signal in RF transmissions.

[we are not alone]

Interesting question. It would require far more larger ground based arrays or space based systems than we currently have to detect anything on the order of television or radio over 20 light years. Background radiation from the big bang and solar activity would garble it and the signal would be extremely weak. Ofcourse it would be in the interest of any advanced civilisation to scan the heavens for neighbouring civilisations so the species next door could be using much larger reflectors and radio dishes than us. There is no real limit to how large a telescope can be built in space. Human efforts are limited by economic factors but our nearest alien counterparts probably use some form of social hierarchy to organise themselves. This is how other animals organise themselves. From chickens to great apes there is a pecking order and this was true for humans throughout most of our history. Endeavours such as the Great wall of China and Pyramids were only possible because power was vested in small group of elite dictators. Ofcourse I'm only speculating but life on earth seems to have universally adopted such a management system so I see no reason why convergent evolution couldn't apply on other worlds. Just as the Emperor of China ordered the construction of oceangoing fleets to explore the world an alien dictator could demand the construction of giant space based arrays to seek out radio transmissions from other races.

[Drunk Vegan]

Great, so you're saying our first contact will necessarily be with an alien dictatorship....

And I, for one, welcome our new alien overlords.