So my pops is at it again, this time he found a new thing to go crazy over and it is frustratingly painful to even understand what he means. I tried googling it but again I cant even figure out what the hell it is based on the first few results. He is saying that “dirty electricity” is causing health problems. Apparently (according to him, almost certainly wrong) converting electricity form AC to DC makes it dirty, and hes walking around with a radio listening to the fuzz trying to find it near electronics. It seems to me he is just picking up interference from wifi or microwaves. I didn’t bother to listen to what he did and did not get fuzz from, all I know if my phone has it (duh) and my computer (likely the wireless adapter on top of it). Well, its that or magnetic fields as far as I can guess.
Does anyone know what the hell he is talking about? Hes been over the whole cell phones cause cancer stuff long ago, is this just the same thing with a stupid term attached to it or am I misunderstanding?
There is a tiny bit of truth here, but it is, as always, misunderstood.
Conventional power supplies (pre switch mode power supplies that we see in most products now) use a transformer to drop the voltage to what is needed, and then use a rectifier to turn the AC into DC. The operation of a rectifier does create some radio frequency energy. (Mostly this is due to slight inefficiencies in the way the semiconductor switches, which results in narrow spikes of current as they switch off.) Some of this energy can couple back through the transformer, and thus into the mains supply. If you tune an AM radio off station you can use it find some of this energy. Switch mode power supplies can also create a reasonable amount of RF. There are design rules that limit what they are allowed to create and couple back to the mains, or radiate out.
So far so good.
As always, it just gets silly from this point on. You have to work reasonably hard to find it, and its presence is at a very low energy level. Mains wiring doesn’t radiate anything well (being a balanced pair any field drops off very very quickly). And indeed the idea it has anything to do with health issues is fanciful at best.
What I will add to the question is this. Remember insane power cords for HiFi systems? They all have one interesting feature in common. They have a shield. You can buy shielded mains cable from Belden and others, adding the shielding adds a few tens of percent to the cost. But shielding a mains cord can be a good idea. Why? Because it stops it radiating any residual RF created by the power supply in the equipment it supplies. It isn’t about getting some mystical perfect feed of power, it simply keeps any mains hash from coupling to the rest of the cables behind your HiFi. The noise may be common mode, but the common mode rejection of a typical feedback circuit in your gear isn’t infinitely capable. Intermodulation components are a real issue, and keeping it all clean may help in some circumstances. So a $5 shielded cable can be better than a $3 unshielded one. This is directly attacking the RF noise of the OP.
Good design of recitfier circuits will use fast recovery diodes and/or snubber circuits to control the generation of switching hash, and they will radiate much less. But you only tend to see that in higher quality systems.
But in context, this really is down in the margins. As noted, there is so so much electromagnetic noise around us that this source is so insignificant as to be almost unknown.
many/most people don’t know how they fit in the whole cosmic whatever. this is upsetting to many. they seek explanations that make them feel better.
people generate explanations and sell them to people. there is good money in that.
people are easily confused about science, technology and health.
some claim all but direct current is bad. some claim all but electricity from our planet and sun is bad. some say that 60 Hz AC (as god intended electrical power to be) is OK but higher frequencies on nonsinusoidal wave forms are bad. things easily noticed (wires, sparks, static) become signs of danger with the leap that it’s the cause of all illness.
this is not to say that electromagnetic effects don’t affect living things. it sure does, some of it makes life possible. other parts of it may have no effect. some parts may be bad.
many things makes illness happen. living longer lets illness happen. we certainly have changed our environment in many ways that have negative impact on people as a whole.
As pointed out, there can be some RFI from almost any device is you measurement is sensitive enough. Certainly some items are worse than others.
I’m into HF/shortwave radio and there’s a few things around the house I have to turn off when I play radio or I can hear them in the static. One is the high voltage ion air cleaner, there’s a sealed lead acid battery charger and one of my laptop power supplies (though I think this is actually the battery charging circuit inside the laptop throwing out the hash).
I’d imagine that the microwave oven is also pretty noisy.
Certainly, though, these are all relatively low power sources and I can hear them in my transceiver due to the proximity to the source. You’ll recall that power drops off very rapidly as distance increases in compliance with the inverse square law. Compared to the signals from broadcast transmitters, pager and cell towers, aircraft navigation instruments, public safety and commercial two way systems, utility telemetry, satellite tv/comm/nav and a thousand others that blanket most of the inhabited planet, local sources are pretty insignificant.
If the OP’s father can barely hear a power supply in the static on an AM radio, visualize how much power is received when a loud and clear broadcast channel is tuned. We are exposed to these signals all the time and I’m not aware of any known health ramifications.
[QUOTE=Francis Vaughan]
Remember insane power cords for HiFi systems? They all have one interesting feature in common. They have a shield. […snip…]
Why? Because it stops it radiating any residual RF created by the power supply in the equipment it supplies.
[/quote]
I’m not familiar with shielded AC power cables but wouldn’t the noise from the hifi power supply be unaffected by the shielding once ‘in the system?’
Hmmph, tell him he lives on the surface of a generator, and every time he travels across its magnetic fields he is inducing a current in himself, and this is also affected sometimes by the magnetic fields generated by that other large round shiny object in the solar system - then maybe tell him that his perfectly plain ordinary transistor radio will generate a magnetic field that is in excess of both of these, and at all sorts of frequencies - that transistor is doing him more damage, if any, than all his other appliances put together - which is zero, and zero plus zero doesn’t add up to a whole lot.
You might also mention that he can be hit by high frequencies, or the low ones produced by the power grid and he can’t do a damn thing about it unless he wants to live in Alaska or perhaps the Russian steppes.
There is a reason why we attempt to use sinusoidal current in our generation systems, but this is pretty much an unnatural phenomenon, unless you are prepared to use some pretty horrendous maths to prove that all varying signals are comprised of a number of different sinusoidal components. In fact it is extraordinarily difficult to produce and transmit a perfect sinusoidal waveform, stuff keeps happening to contaminate it - to the extent that no power grid can produce and transmit ‘clean’ sinusoidal power.
It is only relatively recently that we have been able to produce and transmit high D.C power and then there are lost of issues - so we continue with A.C and the consequent need to convert it to D.C
To continue this a little further, modern switch mode power supplies, instead of running the AC from the mains directly into a transformer (at 60hz), first rectify the AC to DC and then convert to high frequency AC (tens or hundreds of kilohertz). The higher the frequency, the smaller the magnetics, more or less, and only to a point. This can aggravate RFI (radio frequency interference) but as long as it remains under FCC standards (Part 15) it can be sold in the U.S. But this is all about playing nice with other devices in your house, not for any health reasons.
It certainly is, in China. The problem there is that they are burning coal to generate electricity rather than use a non-polluting technology like nuclear power or using scrubbers to remove the pollutants. This begets smog which causes health problems.
You need to ground it though. Not to the house ground, heavens - the evil will leak back in. Drive a separate copper electrode to the ground water level and hook up to this with a shielded, twisted, multi-strand, oxygen-free copper cable, at leat 2 awg.
I’m assuming he’s talking about the ripple effect you get from rectifying AC to DC. I thought properly sized capacitors would normally smooth out any variations in the DC output.
Short version: electricity spreads like ripples on a pond.
If a tiny bit leaks out of something, it keeps going.
Sharp, hard, sudden sources of the electromagnetic energy (‘radiation’) could hurt you. (Too many X-rays, say.)
You aren’t in much danger day-to-day. Bees are more of a threat.
