It's not intrinsic, no. It's possible to design a receiver with its local oscillator emissions to be down to an arbitrarily low emission standard. (But who actually does that?) And not all reception techniques require a local oscillator at all. Still. My point was merely that with an average radio, which was designed to just not be harmfully interfering, such as typical satellite TV receiver? It's quite possibly lit up like a beacon if you know what to look for.
> with its local oscillator emissions to be down to an arbitrarily low emission standard. (But who actually does that?)
Better testing to compliance standards has pushed LOs down way lower than they were in the 40s-60s. We have relatively cheap high quality spectrum analyzers and big integrated measurements. So-- kinda everyone pushes things down pretty low now.
> My point was merely that with an average radio, which was designed to just not be harmfully interfering, such as typical satellite TV receiver?
Yah-- this LNB looks just like a satellite TV receiver, with the exact same LO frequency. So your rogue downlink looks exactly like something that there's hundreds of innocent versions around.
Then a SDR inside your house chooses a different signal from the transponder and gets the data.
The point is, there's a whole lot of (mostly legal) satellite receivers around, so looking for satellite receivers doesn't seem like a great way to spot dissidents immediately.
It's trivial to force all the registered satellite broadcasters servicing a country off-air, if your already willing to arrest the former prime minister in public view, so anyone left with a hot dish would be easily identifiable.
So, you turn off all the state TV coming by satellite... so that you hope that all the satellite receivers get unplugged from the wall (else, they're likely to be listening to reacquire and get program guide etc)... so that you can drive around in vans and look for the -remaining- satellite receivers as a conduit of information coming in.
I mean, I guess it's possible. But probably not your top priority during a time of potential unrest. And it probably won't work that well as a way to find people with the links.
Any non zero amount of incoming radio signal to a hot dish would be suspicious, and easily identifiable, if all the registered broadcasters are offline.
