Power supply radio noise

[Shrek]

Do they cover radio noise for computer power supplies? is it part of the ATX spec?

 

[Bill_Bright]

Search - 2.1a - ID:336521 | ATX Version 3 Multi Rail Desktop Platform Power Supply

Search - 2.1a - ID:336521 | ATX Version 3 Multi Rail Desktop Platform Power Supply

 

[eidairaman1]

Do they cover radio noise for computer power supplies? is it part of the ATX spec?

FCC part 15, spreadspectrum was created for that reason, not sure if it can be disabled as i dont see motherboards with a setting to switch it off now

They put metal beads on some cords to prevent emi

 

[Bill_Bright]

They put metal beads on some cords to prevent emi

There are also 1000 finger tines surrounding every port on the rear I/O shield for the motherboard where it mates with the case, plus about a dozen grounding points where motherboards mount to the case, plus at least one, typically several grounds in every power and data cable, plus every expansion card, the PSU and most other add-ons have multiple grounding points to, among other reasons, either block incoming EMI/RFI from other nearby electronics or to suppress outgoing EMI/RFI from interfering with other nearby electronics.

Then as eidairaman1 notes beads, chokes and other solutions are added to help too.

 

[Shrek]

I'm concerned with radio being sent back out of the mains cable where ferrite chokes are not common.

 

[Bill_Bright]

I'm concerned with radio being sent back out of the mains cable where ferrite chokes are not common.

Sent back out and do what? First off, it would just be switching "chatter", if anything. It would not contain any "intelligence" (data).

Second, let's point out that EMI/RFI suppression is NOT, by any means, just an ATX requirement. There are all sorts of even stricter UL, FCC, DIN and a whole host of other international regulatory agencies that govern the amount of EMI/RFI leakage allowed - and for sure, it is miniscule so it does not interfere with your own TV in the same room, let alone your neighbors electronics interfering with yours.

If your PSU has not been dropped kicked down the stairs - twice - you should not need to be fussing over EMI/RFI emissions getting out, or in.

 

[Carlyle2020hs]

What are we talking here?

Are you afraid to ruin grandpas radio signal?

Are you afraid that your pc can be tracked at the front line?

 

[eidairaman1]

There are also 1000 finger tines surrounding every port on the rear I/O shield for the motherboard where it mates with the case, plus about a dozen grounding points where motherboards mount to the case, plus at least one, typically several grounds in every power and data cable, plus every expansion card, the PSU and most other add-ons have multiple grounding points to, among other reasons, either block incoming EMI/RFI from other nearby electronics or to suppress outgoing EMI/RFI from interfering with other nearby electronics.

Then as eidairaman1 notes beads, chokes and other solutions are added to help too.

Yeah i know about the tangs on the io shield, all for bonding

 

[Shrek]

I have a cheap PC power supply that seems to lack X/Y capacitors at the input.

 

[eidairaman1]

I have a cheap PC power supply that seems to lack X/Y capacitors at the input.

Ok any provisions to add them?

 

[Shrek]

Looks like that is possible.

 

[Bill_Bright]

Yeah i know about the tangs on the io shield, all for bonding

Not sure what you mean by "bonding". Definitely they are for grounding and shielding. That's why that little rectangular piece of metal that inserts into the case is called a shield.

I have a cheap PC power supply

Got a model number? I note even the cheapest of the cheap MUST comply with the various regulations dictated by the FCC, UL and other agencies if the product is to be sold (even imported) into the US. I assume the EU and other jurisdictions that care about interference into their local emergency services, military and commercial services have similar laws and regulations.

 

[Shrek]

Apevia ATX-PR600W Prestige 600W

 

[Wirko]

I have a cheap PC power supply that seems to lack X/Y capacitors at the input.

If that's true then it lacks filter coils too.

 

[Shrek]

What are we talking here?

Are you afraid to ruin grandpas radio signal?

Are you afraid that your pc can be tracked at the front line?

HAM radio interference

 

[Bill_Bright]

It has the FCC and CE logos. That's good enough for me. Now again, that assumes the PSU has not been physically damaged, has a factory defect, or is counterfeit.

As far as HAM radio, as a radio technician for the USAF, I used to be in charge of the maintenance at 2 different MARS stations. So I know a little about RFI and HF radio. This is pretty easy to check out here. If you hear a buzz in your headsets, unplug the computer PSU from the wall. If the buzz goes away, the PSU is a problem. If the buzz remains, something else is.

 

[eidairaman1]

It has the FCC and CE logos. That's good enough for me. Now again, that assumes the PSU has not been physically damaged, has a factory defect, or is counterfeit.

As far as HAM radio, as a radio technician for the USAF, I used to be in charge of the maintenance at 2 different MARS stations. So I know a little about RFI and HF radio. This is pretty easy to check out here. If you hear a buzz in your headsets, unplug the computer PSU from the wall. If the buzz goes away, the PSU is a problem. If the buzz remains, something else is.

A definition of bonding

Grounding and Bonding: Essential Practices for EMC Control - FasterCapital

In the world of Electromagnetic Compatibility (EMC) control, grounding and bonding are two essential practices that are often overlooked. These practices are crucial in ensuring that electrical systems have a low impedance path for fault currents, as well as providing a path for static...

fastercapital.com

The io shield makes contact with the chassis, like the mobo does with the standoffs and the pci cards do with the mounting bracket, the psu makes contact with the chassis and that is the only component directly attached to ground.

 

[Bill_Bright]

That is what I thought you meant by bonding - but not sure. Some refer to bonding as a chemical or thermal "bond" of two or more materials - similar to welding two metals.

 

[eidairaman1]

That is what I thought you meant by bonding - but not sure. Some refer to bonding as a chemical or thermal "bond" of two or more materials - similar to welding two metals.

Landing gear is bonded on an aircraft so that way it doesn't become an antenna itself or build up static charge which can be lethal to a person if they are hit with it right, in a way think of electrical engineers requiring an arc flash suit. Avionics computers are bonded as well.

Heck my truck has 4 bonds for the engine itself due to the efi and ignition system, that doesn't include the sensors using the block as a bond. 1 for the hood, and not sure how many for the cab or fuel pump or transmission. Spark plug wires are spiraled internally so they don't become antennas like a solid core wire does.

 

[Shrek]

Spark plug wires are spiraled internally so they don't become antennas like a solid core wire does.

Didn't know that.

 

[eidairaman1]

Didn't know that.

This lesson was learned in aviation during the use of the otto cycle engine, before the advent of the brayton cycle engine, you don't want stuff interfering with radios and other navaids for use in ifr.

In Bayton Cycle engines you have a he igniter which can kill you like a microwave or a crt, or a pc psu, or radar equipment/high energy radio transmitters.

Ottocycle engines are primarily in the General Aviation category.

 

[Shrek]

500 Ω per foot, no wonder this is only used for spark plug wires.

How recent is this innovation? I don't recall it in cars 40 years ago.

 

[Bill_Bright]

Spark plug wires are spiraled internally so they don't become antennas like a solid core wire does.

Not just to prevent them from becoming antennas. It is just like twisted pair Ethernet. The twists prevent "internal" interference (and crosstalk) too that would degrade the signal big time. It is why you should never run analog audio (speaker or microphone) wires along side AC power - unless you want a bunch of 60Hz hum in your tunes.

 

[Wirko]

500 Ω per foot, no wonder this is only used for spark plug wires.

How recent is this innovation? I don't recall it in cars 40 years ago.

I remember, and it must have been some 40 years ago... I cut apart a spark plug wire and there wasn't even metal inside, it was something that looked like graphite powder.
Why the resistance? My best guess is current limiting. High voltage is needed to ignite a spark, but high current isn't. So if the ignition coil can generate 100 A pulses, and the resistive wire limits that to 20 A, you have 5x less radio interference emitted just by adding resistance. Also, less self-heating in the coil (if that was ever an issue, but I don't know).

 

[eidairaman1]

Not just to prevent them from becoming antennas. It is just like twisted pair Ethernet. The twists prevent "internal" interference (and crosstalk) too that would degrade the signal big time. It is why you should never run analog audio (speaker or microphone) wires along side AC power - unless you want a bunch of 60Hz hum in your tunes.

Yeah I used to do ethernet runs, supposedly the green pair had more tpi than the others.

Jumper wires in cross boxes were twisted, we used black and yello for data and blue and purple for POTs. Copper cable is being phased out at Ma Bell...

I remember, and it must have been some 40 years ago... I cut apart a spark plug wire and there wasn't even metal inside, it was something that looked like graphite powder.
Why the resistance? My best guess is current limiting. High voltage is needed to ignite a spark, but high current isn't. So if the ignition coil can generate 100 A pulses, and the resistive wire limits that to 20 A, you have 5x less radio interference emitted just by adding resistance. Also, less self-heating in the coil (if that was ever an issue, but I don't know).

Yeah that is carbon core also known as spiral core.

It was the advent of HEI that resulted in EMI/RFI becoming a problem for radio equipped transport and even computer equipped transport.