Very well written:
http://www.radioworld.com/Portals/0/Vobbe%20Impact%20of%20Manmade%20Interference%208102016.pdf
It is so well written that I endorse it 100% and cannot think of anything else to say.
This line is one example of a very important point:
This is the reason for the demise of AM radio, have ranted about this on posts in the past.
The commercial stations can't get their signals to the coverage they should be able to. And they pay so much to the FCC for a license.
They just don't care about the AM band.
Haven't noticed this on FM though and since most noise is amplitude modulated and the FM audio is frequency modulated the "AM" is removed at the detector stage of a radio. Very little noise is frequency modulated. If you try to remove the noise from AM you also remove the audio also.
That's the big problem for hobby radio going AM because of this....you won't get your small signal into homes because the noise will drown it out completely.
The 50k watt commercial stations have a hard time getting through it even in their prime broadcasting area.
Yup, before the mid eighties it was never like this. I grew up with AM radio(50s 60s 70s)
Mark
No doubt noise today is at a historic high because of so many interfering devices, but I remember back in the 50s while the AM radio age was still happening there would be massive buzz whenever someone used an electric shaver.
My favorite memory of AM vs. the noise was from the 1980s when a major storm was hitting the area while I was in the car. I was tuned to an all news station which was providing live weather information, but I couldn't hear much because of static, then I stopped under an overpass to wait for a red light and the reception dropped to nothing. Meanwhile the same station's FM outlet was sending wall-to-wall music. I thought they were just plain stupid.
A lot of manufacturers cheat the system to cut costs. The products they submit to the FCC and UL for testing and certification do contain proper RF shielding and interference suppression, but once they get approval and enter production, they "Muntz" the circuit to shave a few cents per unit in manufacturing cost -- you see the space on the circuit board for proper RF chokes and extra filter capacitors, but they aren't actually installed.
And sites like eBay and Amazon are flooded with products sold directly from Chinese manufacturers that don't even try to meet FCC Part 15 or UL standards, and are often counterfeits of name-brand items, especially fake Apple battery chargers and fake Dell/HP/etc. laptop power supplies -- not to mention fake USB flash drives and SD cards that are only a fraction of their advertised storage capacity. These sites do prohibit counterfeit items from being sold, but it's a game of whack-a-mole to catch them all.
I agree with you with the exception of UL and CSA. Both agencies routinly perform audits at manufacturing facilities to compare the approvals to the drawings.