The recent problem isn't the decay rate of RF but the cost of noise attenuation per dollar.
A legal switching power supply in a PC might knock out all AM radio reception on the same desktop. That's because the mfgr installed $5 worth of inductors and bypass capacitors in the power supply input section. So maybe 500 watts output, 4.999 watts of noise gets turned into heat by those interference filters, and 0.001 watts messed up the AM radio on the same desktop.
(edited to add BTW if you think your cheap switching power supply is 99% efficient I have a bridge to sell you... the actual numbers are worse)
The problem is those inductors and capacitors and ferrite cores are $5 of "lost" profit in China, and technically the power supply works with them replaced by pieces of copper wire. So the same 500 watts output, and 5 watts of noise broadcast into the neighborhood. Well, at least its not turned into heat inside the chassis, LOL. The problem is a 5 watt transmitter is going to knock out AM radio for some city blocks in every direction.
In the 30s your average house had like one piece of electronics, probably an old console radio. But now houses are full of electronic junk from China so you're battling pretty much everyone who wants to get the lowest priced XYZ from walmart. Like some forms of pollution, RF interference is virtually impossible to clean up and the biggest violators have a significant payoff, higher profits at the factory and cheaper products on the shelf, or some continuum along that spectrum anyway.
A good analogy would be trying to organic garden in an urban environment surrounded by pollution and pesticide spraying. You might not be dumping god knows what into your dirt, but your neighbors simply don't care and are constantly spraying or dumping who knows what, and you share the environment so even if per UDSA your dirt is legally organic because YOU didn't mess it up, you still know its a regular toxic brew in there because of your neighbors ...
I have no direct experience with power supplies radiating, except to note that switching frequencies are up significantly, from 20khz twenty years ago to 500khz to 2MHZ today. The AM band is something like 700khz to 1.4MHZ.
Higher switching frequencies and the push for higher efficiency[1] also means very fast switch times, on the order of 20-100ns. High speed signals like that contain very strong harmonics which will leak out.
[1] Old guy mentioned to me what you care about is not the efficiency, but the inefficiency. Because that's directly related to heat. Going tom 90% efficient to 95% efficient, who cares! Except you reduced the amount of heat you need to dissipate by half from 10% to 5%.
A legal switching power supply in a PC might knock out all AM radio reception on the same desktop. That's because the mfgr installed $5 worth of inductors and bypass capacitors in the power supply input section. So maybe 500 watts output, 4.999 watts of noise gets turned into heat by those interference filters, and 0.001 watts messed up the AM radio on the same desktop.
(edited to add BTW if you think your cheap switching power supply is 99% efficient I have a bridge to sell you... the actual numbers are worse)
The problem is those inductors and capacitors and ferrite cores are $5 of "lost" profit in China, and technically the power supply works with them replaced by pieces of copper wire. So the same 500 watts output, and 5 watts of noise broadcast into the neighborhood. Well, at least its not turned into heat inside the chassis, LOL. The problem is a 5 watt transmitter is going to knock out AM radio for some city blocks in every direction.
In the 30s your average house had like one piece of electronics, probably an old console radio. But now houses are full of electronic junk from China so you're battling pretty much everyone who wants to get the lowest priced XYZ from walmart. Like some forms of pollution, RF interference is virtually impossible to clean up and the biggest violators have a significant payoff, higher profits at the factory and cheaper products on the shelf, or some continuum along that spectrum anyway.
A good analogy would be trying to organic garden in an urban environment surrounded by pollution and pesticide spraying. You might not be dumping god knows what into your dirt, but your neighbors simply don't care and are constantly spraying or dumping who knows what, and you share the environment so even if per UDSA your dirt is legally organic because YOU didn't mess it up, you still know its a regular toxic brew in there because of your neighbors ...