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Computer causing bad recption

cruizer101

Not really sure if this is the appropriate forum but I reckon people here would be the most likely to be able to help.

We have a sony radio downstairs in the kitchen, which most of the time has alright reception. However sometimes the reception on it is very bad. We recently discovered that what causes the reception to go bad is when I turn on my computer.

Now my computer is in upstairs room at front of house radio is downstairs back of house. The other computer which is downstairs front of house has no effect on the radio when switched on. So I'm wondering does anyone know why this is happening and have any suggestions how to stop it happening.

My only thoughts are either my computer is somehow interfering with the radio signal because it is generating one of its own, or something along the lines of disrupting the power circuit which i doubt as i'm sure the upstairs and downstairs are on different circuits.

Any ideas be greatly appreciated and if this isn't appropriate forum feel free to move or delete or that. Thanks.

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watty

Your power is all one circuit for interference. The "circuits" are just trips or fuses whic have no effect to ANYTHING other than to "open" if there is too much current.

Some computer power supplies, or LCD or CRT omit the filter inside power unit after CE approval so as to save cost.

Is it same with screen power unplugged?

Is it REALLY bad if you wrap 2 to 4 turns of PC mains flex around a portable Radio? (Increasing with each loop of cable).

Is it home built or pre-built brand name?

noelo

cruizer101 wrote: »

Not really sure if this is the appropriate forum but I reckon people here would be the most likely to be able to help.

We have a sony radio downstairs in the kitchen, which most of the time has alright reception. However sometimes the reception on it is very bad. We recently discovered that what causes the reception to go bad is when I turn on my computer.

Now my computer is in upstairs room at front of house radio is downstairs back of house. The other computer which is downstairs front of house has no effect on the radio when switched on. So I'm wondering does anyone know why this is happening and have any suggestions how to stop it happening.

My only thoughts are either my computer is somehow interfering with the radio signal because it is generating one of its own, or something along the lines of disrupting the power circuit which i doubt as i'm sure the upstairs and downstairs are on different circuits.

Any ideas be greatly appreciated and if this isn't appropriate forum feel free to move or delete or that. Thanks.

the simple solution to your problem is relocate the pc. The computer processor is causing your interferance due to it's location and the direction of the incoming radio signal,very much in the same way the microwave oven will with your mobile phone. This witty chap is building up to the concept of the interferance being tranmit via your home electrical installation as EMI and in the suggest a power conditioner. But just repositioning your pc using trial and error should fix your issue,hope this this help buddy.:cool:

Fuzzy Clam

noelo wrote: »

the simple solution to your problem is relocate the pc. The computer processor is causing your interferance due to it's location and the direction of the incoming radio signal,very much in the same way the microwave oven will with your mobile phone. This witty chap is building up to the concept of the interferance being tranmit via your home electrical installation as EMI and in the suggest a power conditioner. But just repositioning your pc using trial and error should fix your issue,hope this this help buddy.:cool:

The suggestion that the problem may be the result of a poor PSU is valid. Some manufactors do omit the filters (Codegen for example). These will kick out much more crap on the radio bands than the processor.
I have had to condition the incoming line to one of my PCs to reduce interference to the radio.
Relocating the PC is not always practical so identifying and isolating the cause is the best option.

noelo

Fuzzy Clam wrote: »

The suggestion that the problem may be the result of a poor PSU is valid. Some manufactors do omit the filters (Codegen for example). These will kick out much more crap on the radio bands than the processor.
I have had to condition the incoming line to one of my PCs to reduce interference to the radio.
Relocating the PC is not always practical so identifying and isolating the cause is the best option.

Indeed its not practical to move your pc around the house and in indeed Emi can and does travel over great distances a simple test for an unexperianced young man should see if your concept is true. plug the radio into the next houses wall socket and see if the emi is being induced into the electrical system. PSU's generally dont do that even under fault conditions,large equipment such as the switching of distribution transformers and veriable speed drives etc etc. but i am say'ing the conditioner didint fix your problem.

Fuzzy Clam

noelo wrote: »

Indeed its not practical to move your pc around the house and in indeed Emi can and does travel over great distances a simple test for an unexperianced young man should see if your concept is true. plug the radio into the next houses wall socket and see if the emi is being induced into the electrical system. PSU's generally dont do that even under fault conditions,large equipment such as the switching of distribution transformers and veriable speed drives etc etc. but i am say'ing the conditioner didint fix your problem.

You're getting stupid now.

Your knowledge of such matters clearly only equals that of the English language!!

watty

It's a well documented scam some manufacturers ommitting the filter parts they had at approval time. The SMPSU is like a wideband jammer. Even next door (or more likely 2 houses up as there are 3 phases and usually each house uses one phase in turn).

PauloMN

I'd try approach the problem from the radio end first tbh, might be less hassle than trying to figure out what's going on at the computer end. Assuming you are listening to local stations on FM, the signal must be quite poor if the computer is causing such bad intereference.

Maybe moving the radio would help - nearer a window and/or higher up (on a shelf or something). Has the radio got an external antenna of any sort? Is it a wire or metal antenna? Try positioning the antenna to maximize reception of the station you are listening to.

Some of the cheaper clock radio types are absolutely appalling in terms of quality. I've an el cheapo clock radio in the kitchen (that's about to head for the recycle centre) and I lose my Newstalk when I stick the toaster on!

Piece of crap. Although, I'd expect better from Sony so probably not the same issue. My yolk is a Bench pos I got in Lidl.

Let us know if it can take an external aerial - might have some ideas then.

PauloMN

watty wrote: »

The SMPSU is like a wideband jammer.

These are a pain for interference. I've a battery charger that I need to plug in on the other side of the house if I want to use my little Sony portable on HF.

With a computer setup, you could have a number of these for printers, external drives etc., and God knows how many more around the house for other purposes.

Every HF user hates them!!!

watty

Get a different charger!

SMPSU can be OK. I have a 24V 5A "brick" model meant for a Laptop universal replacement that works fine on an HF radio.

I have a 12V 3A "plugtop" model that works fine for another HF radio.

We have Server, 3 x switches, 2 x routers, laser printer, MF inkjet Network printer, 5 desktop PCs, 2 netbooks, 7 laptops and none affect HF Radio or the Sony ICF2001D on R4LW.

We have CFL lamps. One Philips and one no-name CFL had to be got rid of. The others are slightly noisey on LW.

But you can get really terrible PCs and stuff.

My laptop SCREEN affects VHF radio (BandII or 2m) nearby, even one handheld on TX! I don't know if it's the multiplex or the CFL backlight's PSU. More than "Arm's length" away, though it's OK.

telecinesk

maby a bit o/t but anyone remember struggling with a zxspectrum to decode rtty or cw and the lethal inteference induced making the radio useless. Funny same inteference comes from my crt monitor 20yrs later so need use lcd screen for radio/pc combination. nothing changes so.

cruizer101

Ok so moving the PC isn't much of an option tbh so i tried moving radio around and no difference really.

So I am guessing it is something to do with my power supply.
The PC is a home build, and the power supply in it is a 'x-power', similar to the one here.

I've tried plugging out the monitor which is a samsung syncmaster 206, so decent brand, and you can hear something on radio alright just as disconnects but no real improvement in reception, this is with radio in same room as pc about 2 metres away.

Also just to say I'm in north county dublin, if that helps at all in terms of how strong and where i am getting reception from.

Edit: forgot to add, my dad uses small radio which he carries around and it runs on batteries, this seems to be unaffected by it

watty

Put two loops of PC mains cable around your dad's radio and see...

TBH the PSU is a cheap one. If there are no warrenty stickers on screws:
1) Disconnect from mains and PC
2) Open cover. Do not touch any wires or PCB as some parts are charged to 300V even when it's off and disconnected.
3) look at where mains wire goes from plug on case where mains plugs in. See does PCB have missing parts (at least two capacitors and one choke), The choke would have had 4 pins and been replaced by two wire links.

I think you will find these parts missing to save money. In which case return it to Maplin as the maker has committed Fraud.

See http://www.compliance-club.com/PLT/PLT%20book.pdf
page 27

4) A practical demonstration
A number of “Grey Import” computer power supplies are being
marketed in the UK which, although CE marked, have key EMC
related components omitted. Trading Standards have been
informed – but that is another story. These PSUs are very useful
as sources to explore the capability of indoor PLT to tolerate
interference, because they can be fitted with external filters
crafted to produce any desired level of conducted emissions.
By this means we can model the performance that would be
achieved by a CISPR22-conforming PLT system by raising the
interference environment to restore parity with the PLT modems.
External filters were used to establish the dotted red curve in
Figure 2. For this test the sending and receiving modems and
the interferer PSU were all plugged in to the same socket strip,
which was powered via a CISPR16 LISN to provide a defined
circuit impedance and isolation from any remote interferers.
The QP emission spectrum of the “Xpower” ATX-400TD PSU
with external filter “C” is 20dB above that expected from a
product compliant with the CISPR22 Class B limit within the
PLT band of 3 to 30MHz, as may be seen in Figure 3 below.

Looks like this PSU is a known culprit!

cruizer101

Looks like I'm missing some bits :eek:

It has some warranty stickers, although i did my best to keep them in tact, but it is also over two years old and i very much doubt i have box or receipt anymore.

So I opened it up and I think you are right there are a couple of marked slots for capacitors which are empty, and also some components which appear to have been replaced by some wires.

I've attached image, you can see a suspicious lack of components at the top of pic.

So now its established what the problem is have to figure out what to do.
As I said PSU is over two years old so going back to Maplin not much of an option I'm guessing, although I might give it a go anyway.

Can the problem be fixed or is it just a case of getting a new PSU.

watty

Even up to 5 years they could be obliged by Sale of Good act.

A new PSU might also be fraudulent in its CE mark

In theory if you are competent at soldering, the missing parts can be fitted.

FIVE filter capacitors and TWO RF chokes (dual winding toroid inductors).

Criminal. Literally.
Probably wiping out LW radio reception for several houses. And the not as evil Homeplug network adaptors won't work!

pixbyjohn

I had an interference problem on my HF transceiver when I bought a new computer which I used for Digimodes. I changed the PSU and all was well.
Now the background to this: I was lucky enough to work in IT and how I cured the problem was by using one of 300 computers in my care until I got one that didn't cause interference. So I took the PSU from that and replaced the PSU from my new machine, all interference gone. Now the PSU that I removed from my machine is still working away in my place of work without any problems at all.
Hope this helps you.

Mike 1972

Quickest way to determine whether interference is mainsborne of radiated is to try running the affected radio (where possible) on batteries to see if it makes much difference

watty wrote: »

It's a well documented scam some manufacturers ommitting the filter parts they had at approval time. The SMPSU is like a wideband jammer.

How come noone is ever prosecuted for this given the amount of effort that is put into locating and closing down pirate radio stations (which frequently arent causing interference at all whatever COMREG/OFCOM say).

I mean for every one instance of interference caused by a pirate there must be hundreds (probably thousands) of cases of badly designed electrical equipment messing up someones radio/TV reception. :mad:

PauloMN wrote: »

Although, I'd expect better from Sony .

In my experience Sony radios while generally better than average can very widely in RF performance/quality of design between models.
Regardless of manufacturer consumer clock radios very from indifferent to awful. Bar an ancient (and huge) Ferguson (IIRC) model which retailed for 50 quid in the early eighties.

watty

Some new points on PLT/comtrend/homeplug interference here.
http://www.techtir.ie/node/1001843

Money Mike 1972.

Regulators more interested in Protecting Big Business than protecting Consumers.