While base frequency is 240KHz it is also not a sine wave so has loads of harmonics.
Good quality SMPSUs all have metal shields. They are often offered as an optional extra and will not be listed by cheap suppliers.
I can remember a new processor based device going out for trial and coming back because the processor kept crashing.
Engineers had to tell the buyers/bankers that it would never work without the shield. The bankers hated having to buy shields for all those power supplies.
Class D amplifiers are the same. They always have to go in a shield if there is a radio in the same unit. Look at a car radio being taken to bits on U-tube and you will see the radio bit in a little soldered shut box with the aerial wire going in on the side furthest from the class D amplifier.
I can remember a new processor based device going out for trial and coming back because the processor kept crashing.
Engineers had to tell the buyers/bankers that it would never work without the shield. The bankers hated having to buy shields for all those power supplies.
Class D amplifiers are the same. They always have to go in a shield if there is a radio in the same unit. Look at a car radio being taken to bits on U-tube and you will see the radio bit in a little soldered shut box with the aerial wire going in on the side furthest from the class D amplifier.
A long time ago I was involved in HAM radio. I lost interest once electronic speedcontrols and light dimemrs started to get used since it killed off the DX reception. Spurious noise all over the place, the same with PLL oscilaltors at the time, noisy sidebands. FWIW I worked with 5 Watt on CW all countries from rural New Zealand, once moved to the big cities the noise was too much.
Noise slop has definintely gotten Out Of Hand.
Blame the FCC, and all those new manufacturers of their annoying products.
About FCC Part 15 Regulation:
"FCC Part 15 is a federal regulation that sets limitations on the amount of electromagnetic interference allowed from digital and electronic devices such as wristwatches, musical instruments, computers, telephones, and low power transmitters."
Don't blame SMPS for this - they are governed by regulations more strict than the general lighting BS. A company serious about making SMPS will invest in (1) EMI compliance receiver and an appropriate shielded chamber for measurement. (2) Engineers sufficiently experienced to know what the heck they're doing (3) Line surge generation equipment to make sure your cherished SMPS isn't crippled by the first transient to come down the line (there are many of various types). (4) Evaluation equipment to make sure that the first dumbo that shuffles across the carpet and touches something (an ESD event) doesn't cause failure or a restart that causes your computer full of precious data to lose its mind. (5) Employees who actually know how to lay out a competently designed SMPS PCB. People not willing to make that sort of investment have no business manufacturing SMPS for the general public, who have absolutely no idea how hostile the environment is for an "innocent" SMPS cast out to encounter the cold, cruel world.
Quite a number of devices fall under FCC Part 18 which has less stringent regulation of emissions.
Try listening to an AM radio station when you're driving through Times Square NYC -- impossible.
Part 18 was a lousy thing to add to regulations.... see?...... like you stated, making some radio unlistenable.
It's no wonder people have been driven to streaming, Sirius XM, etc.... enitcing/forcing people to buy new equipment, subscriptions.. more revenue for the greedy commerce to milk.
broadways -
Upon reflection, I think that the SMPS you got was a "copy without understanding" of someone else's design, especially as some commonly known measures for abating EMI were ignored. Copying is rampant in the electronics arena. I used to call on a customer whose entire business was based on copying one well-known SMPS manufacturer's designs.
Upon reflection, I think that the SMPS you got was a "copy without understanding" of someone else's design, especially as some commonly known measures for abating EMI were ignored. Copying is rampant in the electronics arena. I used to call on a customer whose entire business was based on copying one well-known SMPS manufacturer's designs.
Jim Brown a retired AES go-to interference expert covers the problem is several of his papers & Power Points:
http://www.audiosystemsgroup.com/publish.htm
http://www.audiosystemsgroup.com/publish.htm