Computer Generated Noise

[rijo101]

Hi Group , I have a problem with my home computer and or monitor
generating noise that is picked up on my HF ham radio rig . In order to
cancel the generated noise , how might be the best way to ground or
choke out the noise directly from my home PC ? I presume I first need to
determine the frequency of the unwanted noise signal and then build a
balun or a choke to ground or cancel the noise, maybe !!!
One thing is for sure , the problem exists when the computer is on
and it generates harmonics that interfere with HF radio on Amateur Radio
Frequencies .
Thanks for any good help in advance , rijo

 

[James Sweet]

Hi Group , I have a problem with my home computer and or monitor
generating noise that is picked up on my HF ham radio rig . In order to
cancel the generated noise , how might be the best way to ground or
choke out the noise directly from my home PC ? I presume I first need to
determine the frequency of the unwanted noise signal and then build a
balun or a choke to ground or cancel the noise, maybe !!!
One thing is for sure , the problem exists when the computer is on
and it generates harmonics that interfere with HF radio on Amateur Radio
Frequencies .
Thanks for any good help in advance , rijo

Is your computer plugged into a properly grounded outlet? Got all the
metal slot covers in place? Computers produce a lot of RFI, it can be
tricky to keep it contained.

 

[Adrian C]

This has to be an FAQ on amateur radio groups, or answered in full on a
ham related website.

The answer is basically clip-on ferrite chokes for external leads,
ensuring that the motherboard is grounded at all mounting points (no
plastic standoffs), ensuring the back plates of add-on cards and sockets
firmly and electrically contact the backplane slots, ensuring the edges
of the metal case cover firmly and electrically meet the rest of the
case, covering up holes larger than 1cm diameter etc. Get plenty of
adhesive copper tape/foam.

If all else fails, turn on "Spread Spectrum" in the BIOS setup ;-)

 

[Charles Schuler]

Hi Group , I have a problem with my home computer and or monitor
generating noise that is picked up on my HF ham radio rig . In order to
cancel the generated noise , how might be the best way to ground or
choke out the noise directly from my home PC ? I presume I first need to
determine the frequency of the unwanted noise signal and then build a
balun or a choke to ground or cancel the noise, maybe !!!
One thing is for sure , the problem exists when the computer is on
and it generates harmonics that interfere with HF radio on Amateur Radio
Frequencies .

This is a tough problem because, generally, the noise is radiated from the
computer circuit boards. The waveforms in computers are rich in harmonics,
thus there is no easy way to filter the noise out. However, you can try:

1/ Physical separation between the computer and the antenna. (Sometimes a
simple reorientation of the equipment can help.)
2/ Is your antenna feedline coaxial? If so, a balun at the antenna can help
(this is because balanced currents in the coax helps to prevent the shield
from acting as an antenna).
3/ Use separate ac supplies and line filters.
4/ Use ferrite decoupling cores on all of the computer leads.
5/ Replace long leads with short leads.

 

[rijo101]

Thanks to everyone who replied . I will take all the replies into
consideration . Thanks again.

 

[Mark D. Zacharias]

Thanks to everyone who replied . I will take all the replies into
consideration . Thanks again.

Charles Schuler wrote:

I had this problem largely resolved by replacing the power supply in the
cheapo computer box with a higher quality power supply. Before replacing the
PS, I couldn't listen to AM radio anywhere in the building, now I can.

Mark Z.

 

[PhattyMo]

I had this problem largely resolved by replacing the power supply in the
cheapo computer box with a higher quality power supply. Before replacing the
PS, I couldn't listen to AM radio anywhere in the building, now I can.

Mark Z.

This is a biggie,I've seen a large variance in PSU filtering...
Some cheaper PSU's don't even fit the filtering components to the
PCB's,they jumper over the common-mode chokes,and leave the caps off the
board!

Some PSU's have 2 common mode chokes in series,and alot of filtering...
It depends.

Another tip,If you can fit one,use one of the IEC sockets with the
built-in filtering can on the back on everything in your house that uses
an IEC socket,all the SMPS's in everything now days are nasty.

Ferrite every cable on your PC,at both ends of the cables.
(okay,maybe just one ferrite on the mouse and keyboard,or else it might
get annoying.)

Basically filter the hell out of everything-go overboard with it.
PC's are *horribly* noisy beasts to tame..