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Disrupting AM Radio Signals

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posted on Jul, 14 2005 @ 05:20 PM
Ive wanted to ask this for quite some time, and I know this may not be the best place to put it, but I would like some good answers.

Now this may sound silly, but please read on.

Ive owned 3 computers in the past, only the 2nd one has gave me this issue.

The problem is the computer disrupts AM radio signals. Only AM radio signals. At first I thought it may be a power issue (wiring in the house) or such but the computer has been in different rooms and even different homes and has done the same thing. Im no wireless expert, but the computer has no wireless components that would cause anything.

Currently the computer will absolutely obliderate AM radio a few feet from it. What used to be a crystal clear station becomes utter static and noise. Some 40 feet away the same radio station becomes audible, but still has static and constant noise. It almost sounds like a bandpass noise.

The weird thing is it disrupts the signal outside in our shop as well. This is already quite a considerable distance from the pc. It also disrupts a handheld unit.

It effects all AM radio stations, but not FM. Using the newly bought computer, nothing occurs.

The question is, why? Ive looked it up but never found any related info.

Anyways, thanks.

posted on Jul, 14 2005 @ 05:24 PM
I have this as well, its bloody annoying, I have idea what causes it, but if you plug some earphones in, it does stop. Havent the fooggiest why it does it. Probably like when you put a mobile next to a speaker and it beeps.

posted on Jul, 14 2005 @ 05:41 PM
I have various two-way radios at work and at home, both on UHF and VHF frequencies.

They will "receive" static if put too close to a computer. The same thing happens near gas stations and certain video arcade systems as well.

Additionally, as we all know, when a cell phone rings if it's next to a computer the speakers make noise.

All very interesting stuff added on to what you both talk about.

If someone could post explaining the nature of some of these computer/electronic devices, and their effects on radio frequencies and vice versa that would be very helpful

posted on Jul, 14 2005 @ 07:46 PM
But why does running this one particular pc cause it to happen while the other 2 do not? The components are nearly identical.

posted on Jul, 14 2005 @ 10:47 PM
Not sure about the AM signals (I do know CB's on trucks easily disrupt AM signals).......but I have noticed something weird lately.

I have a cell phone and it stays on. This happens when the phone is not ringing....but every so often, I get interference through my computer and my sounds like morse code almost. I could understand it if my phone was ringing...but it doesn' is just laying there....damn these electronics

posted on Jul, 14 2005 @ 11:09 PM
most computers are not shielded very well and emit all types of frequencies...Monitors and video cards emit a wide range of frequencies as well...

[edit on 14-7-2005 by XPhiles]

[edit on 14-7-2005 by XPhiles]


posted on Jul, 14 2005 @ 11:55 PM
As above, electronics, particulary computers filled with oscillating crystals and massive amounts of copper create tons and tons of sideband radio interference. This is the speaker noise cellular phones create when you have them too close to a speaker or some other sort of audible pickup device.
Solution? ... well... besides a bunch of shielding... live with it.
Just a consequence of these high frequency electronics we know and love today.

But why does running this one particular pc cause it to happen while the other 2 do not? The components are nearly identical.

Nearly identical is the key word there... the motherboard itself could be generating the interference you are picking up. Any other differing parts could be generating it. Even a combination of these parts could be the cause. In any case, it's perfectly normal, although annoying.

posted on Jul, 15 2005 @ 12:12 AM
I could see shielding being one of the causes. Ive done the same thing with my Fender Strat guitar to get rid of the noise it produces, much the same really.

posted on Jul, 15 2005 @ 01:12 AM
I would suspect the source would be a combination of SMPS and shielding.
I find Antec computer cases to be pretty fair at shielding. Enlight was also but
I do not like the newer cases. The most likely source of RF of any power would
be the power supply. Other sources tend to be much lower power and ranged.
If the power supply is using SMPS, it is a significant RF generator. And naturally,
it would impact Amplitude Modulated (AM) signals far more than Frequency Modulated
(FM) signals. Try placing the computer in a marked, central position. Take a portable
AM radio and walk around the computer. Note where the signal is weakest and where strongest.
assuming you are not running the cpu with the case half dis-assembled, you will find that this experiment
will probably indicate the rear of the case. If you had a spectrum analyizer handy, you can tell the
strength of the signal and the spread spectrum frequencies. But I would suspect the source is
probably the open (grid) area around the exhaust fan of the Power Supply. If so, take a small
disposable pie pan (Metal, aluminum will work) Turn this into a little duct that redirects the
fan output upward but otherwise encloses the opening. Use metal tape to attach, as it does nothing
unless it acts as an extension to the conductivity of the computer case.
If you are an experimenter and have many knock-outs missing at the rear, or the front assessory
area then YOU are the source. Your cpu box is a Faraday cage for a reason.

SMPS - Switching mode power supplies in depth coverage :

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