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What power amplifiers emit little or no electromagnetic radiation?
What power amplifiers emit little or no electromagnetic radiation?
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Old 12th September 2020, 02:37 AM   #11
H713 is offline H713  United States
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Most of this is at such a low power level, I had assumed that this just needed to be quiet to avoid interfering with some sensitive equipment or another. The number of switching power supplies in the world can be a real pain when dealing with sensitive, single-ended input instrumentation, for example.


Approaching from the point of view of "this 500W amplifier is sitting in a rack next to a poorly shielded RF preamp", you would be wise to choose something with a linear power supply and a class AB output.



From the point of view of people who are worried about health impacts...
People (Hams, RF engineers, etc) have been building RF and microwave amplifier circuits for 100 years now without issue. The noise emitted by a class D amplifier or a switching power supply is just that- noise. It is many orders of magnitude lower in power than even a handheld transceiver.



As an experiment, hold your AM radio close to a brushed AC or DC motor (often called a universal motor) as it runs. Even very simple things can create surprising amounts of noise, far above what a well-designed class D amplifier emits.
 
Old 12th September 2020, 11:22 AM   #12
CowCat is offline CowCat
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I'm trying to minimize all forms of electromagnetic radiation except visible light and infrared light whenever possible as a rule of thumb.

It's about health for me.

I also try to minimize electric field and magnetic field. Even my wired mouse emits less EMF than other wired mice. I'm optimizing my environment slowly.
 
Old 12th September 2020, 04:02 PM   #13
H713 is offline H713  United States
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I'm sure you've had plenty of people explain the difference between ionizing and non-ionizing radiation before, and I'm sure at least one person has done the calculation to show that electromagnetic waves below the ultraviolet portion of the spectrum have insufficient energy to ionize the atoms and molecules in your DNA (which is what causes genetic damage and can lead to cancer). I won't get into that.

Audio power amps are usually reasonably quiet. Poorly filtered class D amplifiers may be an exception. Even some switching power supplies aren't too bad. With the covers on, I really couldn't measure too much noise from the QSC PL230 I had on the bench even under reasonably heavy load. Of course, if you're trying to eliminate power supply switching noise you've got one seriously long uphill battle.

I go through this process every so often in my lab when I need to design really sensitive circuits. Biggest offenders are...

1) LED Lighting. Cheap LED lights are terrible in this regard, usually because Americans demand lower and lower prices, and the quality of the switching power supplies is usually the first thing to the chopping block. Powering LED lighting off a linear power supply helps.

2) 13.56 MHz noise from the Metcal. Yeah, it's not perfectly shielded. It's really pretty good, but it's caused a problem once or twice. It's a necessary evil for those who want an uncompromised soldering experience. It heats up so quickly, however, that it's really easy to just turn it off when I need to take a measurement.

3) Noise from crusty computer power supplies and networking equipment. Even the good ones aren't perfect, but the bad ones are a lot worse.

4) Everything else including amplifiers and a lot of test equipment.
 
Old 13th September 2020, 12:36 PM   #14
H713 is offline H713  United States
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Again, I'm not getting into the subject of supposed health effects of non-ionizing radiation. My background is physics not biology. As a warning, however, there are a lot of studies on the subject that have been biased or grossly misinterpreted. I do not have the time to comb over every study someone links to, and you are not hurting anyone by trying to minimize your own exposure. Be warned, however, that there are a great many products that claim to do things to reduce your exposure, but in fact equate to installing spikes on the bottom of your preamplifier (that is, they do nothing at all).

All of that is to say, if you want to do this, don't believe everything you read on the internet.

I will, however, point out that humans have been living with RF transmitters for over a century now. I know a good many ham radio operators who are now in their 70s and 80s who have been running legal limit for decades and have gone through a good many 3-500Zs. If it were me, I would first try to minimize my own exposure to potentially toxic chemicals including pesticides, cleaning products, air pollution and fast food.
 
Old 14th September 2020, 09:15 AM   #15
H713 is offline H713  United States
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The research done on this particular subject has been largely inconclusive, with most papers stating that more research needs to be done. Because of that, and because we've been living with RF electromagnetic fields for over 100 years now, I would be very hesitant to describe it as being "the new cigarette". Furthermore, many studies that suggested a possible link between RF exposure and certain types of cancer looked at data for people whose occupation or hobby (in the case of amateur radio) involved significant amounts of RF exposure. It should of course be noted (and may of these studies do note this) that many of these people are necessarily exposed to potentially hazardous chemicals including soldering fumes and even PCBs. As an example, a lot of magnetrons, klystrons and other transmitting tubes use a beryllium oxide ceramic in their construction. There is no need to question whether this is hazardous.

As you mentioned, there appears to be some evidence to suggest that there are some cellular-level impacts of non-ionizing electromagnetic radiation. How significant it is, I cannot say.

What I will say, however, is that there is a distressing uprising in the number of people who believe that RF exposure is "extremely dangerous", when few credible studies have yielded any conclusive information. Unfortunately, it often leads to the spreading of misinformation that ignores the fundamentals of modern physics.

I will close with one final thought. We live in a time where misinformation spreads faster than ever, and many Americans take what they read on social media as fact. Most of the big studies that have been done on the subject of how non-ionizing electromagnetic radiation affects living organisms have not come to any certain conclusions. Inconclusive results are just that- no definite conclusions could be drawn one way or another. In the absence of known information, it is perfectly reasonable for people to take extra precautions and there is no shame in doing so. With that said, exposure to this type of non-ionizing radiation is not new. Microwave radar was developed during WWII, and high power transmitters for HF, VHF and UHF broadcast and communication have been in operation since the 1920s, though power levels remained relatively low in the early years. More personal communication devices like handheld radios have been common for nearly half a century now. If there are some minor negative health effects, they need to be weighed against the value this technology provides. For me, as an amateur radio operator and someone involved in research that utilizes high-power electromagnetic fields, that decision is easy to make.

That is all I will say on this particular subject.

H-713

Last edited by Variac; 15th September 2020 at 11:43 PM.
 
Old 14th September 2020, 11:53 AM   #16
billshurv is offline billshurv  United Kingdom
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What power amplifiers emit little or no electromagnetic radiation?
The largest polluter in your house (assuming you eshew a mobile phone and wifi at home) is your computer. That would be where I would focus efforts on reducing RF emissions in the house. Chosing a wireless over wired mouse seems very inconsistent with your efforts though.
 
Old 14th September 2020, 01:08 PM   #17
kevinahcc20 is offline kevinahcc20  United States
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In the 1960s when I was a teen there were no computers, no wifi, no switch-mode power supplies, no microwave ovens, no 4GLTE, no 5G...the EM spectrum was very quiet compared to now. At that time the WWI generation born late in the 19th century was departing and the typical age at departure was late-60s to mid-70s. Admittedly there were some who made it to their 80s and a very few who saw 90s, but somewhere in the early 70s was typical.

Fast forward half a century and we are hip deep in people far into their 80s and reaching 90 is no longer the milestone it used to be. A chart is instructive:

Click the image to open in full size.

Many things contribute to this, the abrupt dip in the late 19-teens combining the effects of WWI and most significantly the Spanish Influenza. Lowering infant mortality is also a significant factor. But how could you possibly conclude in the face of this that the ubiquitous growth in the e-m environment in the last 30 to 40 years is "the new smoking"?
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Old 15th September 2020, 01:16 PM   #18
Mooly is offline Mooly  United Kingdom
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What power amplifiers emit little or no electromagnetic radiation?


CowCat... several of your posts have been deleted. Please read the rules on what constitutes acceptable posting.

Conspiracy theories, political theories and medical issues are prohibited topics.
 
Old 15th September 2020, 11:07 PM   #19
egellings is offline egellings  United States
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If it ain't oscillating, the linear amp has no HF garbage to spray around.
 
Old 16th September 2020, 05:12 AM   #20
H713 is offline H713  United States
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CowCat,


As far as I know there are no rules against straying off-topic or pushing the OP to reconsider what they are looking for. Perhaps the mods can correct me if I am wrong, but a good many threads on this forum stray quite far from the original topic.



Also, because it was brought up, some Class D amps can spray a lot of noise around if they aren't well filtered. They are becoming much less common, however. Most of the electromagnetic noise that comes from a modern amplifier is unavoidable because of the high currents in the output stage to drive the speakers. Your speaker cables, unless tightly twisted, will also contribute to this.
 

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