eHam.net - Amateur Radio (Ham Radio) Community

Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net



[Articles Home]  [Add Article]  

RFI Noise and Inexpensive Computer Power Supplies

from Larry Kirkland, W4LK on August 6, 2007
View comments about this article!


I recently decided I was going to make good use of George Bush's $600 tax refund and upgrade my old hamshack computer to 21st century standards. It had served me well, was reasonably noise-free, and it had the essentials for an easy upgrade project. I decided to re-use everything but the motherboard, memory, and video card.

So with good intentions and George's check, I attended a regional hamfest that had several computer dealers competing against each other. After a couple of hours of fighting my way up to the counters to see what was being offered, I settled on a whiz bang deal with all the stuff I needed to make the upgrade. They also included a new case with power supply to package it all in.

The next day was spent building up the new computer using some of the stuff salvaged from my old clunker. I took advantage of the new case/power supply because it was rated at a higher wattage than the old box. The good news is that everything started up OK and functioned great. The speed was unreal (1.4 gigahertz). The audio and video were awe-inspiring. I had joined the 21st century!

It was time for our state MARS net just above the top end of 75 meters, so I turned on the rig to get ready. At first I thought we were in the middle of a solar storm! The noise on frequency was over S-9. Signals were way down under the noise. I tried different bands - 80 and 40 were wiped out, but 20 and 15 were better. Then it hit me - the new/upgraded computer was turned on and could be generating the hash! Sure nuff, when I shut the computer down, the noise went away.

I fired it back up and began unplugging cables from the back of the computers to see if I could determine what was radiating the noise. To make a long story short, even with everything unplugged except the power cord, the noise was still there. Then I tried one of those snap-on torroids on the power cable and the noise went down a few db's. AHA! That means the noise was leaking out into the power lines through the power cord and being radiated. Problem diagnosed!

I should have had a clue that all this was likely because the computer vendor was selling this case/power supply jewel for a little more than $30. I cleverly removed 4 screws holding the power supply to the case, removed the power supply and took out the 4 screws holding the little cover on. As I suspected, there was absolutely no filtering or bypassing of the 110V line. Zilch. Another good example of you get what you pay for. Fortunately there was plenty of room at the back of the power plug socket in the power supply to add a brute force line filter. These are described in the ARRL handbook and consist of four .01 f disc ceramic capacitors and a pair of RF chokes. The chokes must be capable of handling the current requirements of the computer, and the voltage rating of the capacitors should be 800V DC or greater. The parts are probably in your junk box or are available at Radio Shack. It took about 30 minutes to solder the parts in and the mod completely removed any trace of noise.

So, if you are experiencing computer noise and your computer has one of those el-cheapo cases/power supplies, you might want to consider adding the brute force line filter mod. It works for me.

Member Comments:
This article has expired. No more comments may be added.
 
RFI Noise and Inexpensive Computer Power Supplies  
by VK4TJF on August 6, 2007 Mail this to a friend!
yes i had the same problem with a state of the art computer that my brother in law built for me. i just took the power cord and used some brute force strength and wrapped the power cord as many times as i could around a big ferrite rod and tapped it in place with electrical tape. then i spent some money on snap on some ferrite rings as well. in the end the noise came down.
 
RFI Noise and Inexpensive Computer Power Supplies  
by K9MI on August 6, 2007 Mail this to a friend!
I learned my lesson on this problem also, just about the same scenario of buying an inexpensive case for a new pc I would be putting together. 40/80/160 were useless with the PC on. I tried a few things with no luck, and I asked my son what case/ps they used where he worked at, which was Antec. That took care of the problem, and if I need a new ps for a computer, that is the brand I look for.

73, Mike K9MI

 
RFI Noise and Inexpensive Computer Power Supplies  
by K4QO on August 6, 2007 Mail this to a friend!
I the same problem with my wife's new computer. What I found was the power supply had the spots for the filter parts but they we all jumpered past each one in an obvious attempt to save money. I took an old broken supply and scavenged parts from it to place in the new supply. Don't do this if you aren't techy enough to figure out what parts go where, etc...

73, Randy K4QO
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W5UDX on August 6, 2007 Mail this to a friend!
Here is a good one.

I bought a new machine in Jan, and I can't seem to figure out what the prob is.

I get a tone from this computer on the radio, but here is the fun part, its only on LSB and it will go away when I unhook the sound card cables from the speakers/radio.

Even more weird, when I run Spectra Plus 5.0 software, I can make the tone move down in freq. from 2.6k (where it normally sits) to sometimes 40Hz, where I can't hear it anymore and yes its on every band but only on LSB.

It sure is the strangest noise prob I've ever had with a computer.

Its a clone 3.4GHz Duo Core 4 gig of ram 500 watt supply Creative Audigy card.

I thought it might have been the video card or monitor but they ck out fine when doing tests switching things out with the old computer.

Has anyone experienced this fun noise project?

Thanks
Greg
w5udx
 
RFI Noise and Inexpensive Computer Power Supplies  
by KQ4KK on August 6, 2007 Mail this to a friend!
Of course,it was George's fault..
 
RFI Noise and Inexpensive Computer Power Supplies  
by N2RRA on August 6, 2007 Mail this to a friend!
Great article!

Maybe you guys can help with this problem.

Not getting any noise from the P.C. or transformer itself, but from the monitor.

Only when I turn the monitor "On" is when I get warble type sound till it spike's 5-9+. Turn the VFO will get rid of it till it catch's up again.

What is this?
How do I get rid of it?
Do I have to wrap my monitor in foil? Hi!

Tnx!
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W5GNB on August 6, 2007 Mail this to a friend!
In addition to the radiation problems associated with computer hardware, you must remember that these "signals" have to be picked up by the antenna system before it can become a problem.

It is possible that you might have a shielding problem or perhaps the antenna system is too close to the area where the computer is located thus causing the interferrence to your receivers.

Fortunately I have pleanty of room here to place my antennas far from the shack so I have not experienced any problems that have been described. If you have the ability to put the antennas some distance from the radio room, you may eliminate these problems.

73's
Gary - W5GNB


 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W4LGH on August 6, 2007 Mail this to a friend!
ALL switchmode power supplies will radiate, if not properly grounded and shielded. I have found cheap ones that were quiet as a mouse, and expensive ones that would get into everything. Price really has nothing to do with it. However there are several PS makers that say their PS is quiet, and these are the ones you need to look for!

If using a switch mode PS to run your shack, you could get noise from that as well. Had an Astron SS-30M once that the would get into all of my radios. Was getting ready to toss it, when I found ALL of the
CHASSIS BOLTS lose...tightened an dall was fine.

73 de W4LHJ - Alsn
http://www.w4lgh/com
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KE3WD on August 6, 2007 Mail this to a friend!
Would anybody who makes reference to the ages old IRS refund check as being, "George Bush's check" be likely to be the same kind of person who would not do their homework regarding the PSU for the shack puter and go with a thirty dollar case?


The lost art of critical thinking.


And then write an article about it...



.

 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W4CBL on August 6, 2007 Mail this to a friend!
*********************************************************
Would anybody who makes reference to the ages old IRS refund check as being, "George Bush's check" be likely to be the same kind of person who would not do their homework regarding the PSU for the shack puter and go with a thirty dollar case?

The lost art of critical thinking.

And then write an article about it...
*********************************************************


Exactly what I was thinking!

Chris, W4CBL
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by NA4IT on August 6, 2007 Mail this to a friend!
For the fellow with the monitor noise...

Try changing the Video Adapter Refresh Rate. You find in under Display Properties, Settings, Advanced, Adapter.

Good article on the computer PS. I am having the same problem. Going to try the filter approach.

de NA4IT
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KU4IS on August 6, 2007 Mail this to a friend!
FYI, George Bush's $600 refund was a different refund from the "ages old" tax refund...

I have had similar problems with switching power supplies and varying degrees of noise. There's not much filtering you can do to help. I've tried the ferrite snap-ons and they move most of the interference out of the band, but don't completely eliminate it. I finally bought an old Nippon America 13.8v supply that I found at a flea market. It's big, but stable and quiet.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W9PMZ on August 6, 2007 Mail this to a friend!
"George Bush's check"

No, it's your money that you over paid!

This thinking traps you into the concept that a tax cut costs the government. It doesn't cost the governement anything.

They just take in less money.

73,

Carl - W9PMZ
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by N2RRA on August 6, 2007 Mail this to a friend!
NA4IT,

Thank you! I will try that later today. If that doesn't do it do you have any other suggestion's?

Eric
N2RRA
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KE3WD on August 6, 2007 Mail this to a friend!
Can't find George Bush's callsign in the QRZ database.

So how exactly does mentioning him relate to Ham Radio again?


.

 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by WB2TQC on August 6, 2007 Mail this to a friend!
Why does the mention of George Bushs' name have to be defended? It adds nothing to the context of the story and could have been left out without injury. Is it that some of you guys are a bit sensitive, politically??? Who cares that he mentioned Mr Bush? Think he was name-dropping?? I don't get it.

73,

John (WB2TQC)
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W6TH on August 6, 2007 Mail this to a friend!
.
The IRS is not a part of the United States government, but is an organization that is hired by the U.S. government.

The IRS is the hired US government agency responsible for tax collection and tax law enforcement.

We the people should dump them and away goes some of our overhead.

My power supplies are all linear and don't have any switchers in my shack any longer.

.:
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W6TH on August 6, 2007 Mail this to a friend!
.

More RF noise from the IRS.

There are over 2000 workers for the IRS and the building repairs for 2006 amounted to over 25 million dollars, WOW!

How can this racket be filtered out?

.:
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KW1R on August 6, 2007 Mail this to a friend!
Had a similar problem with a lap-top we were using in the shack. However our's was just a bit a different the culprit in this case was the power transformer that plugs in the wall.

Answer: Went to a local electronic's shop (no not Radio Shack) found another transformer same voltage did a very simple bit of re-wiring and Viola' no noise!

Hmmm I'm wondering if the 21st. century advances are all they are cracked up to be?

73
Bob KW1R
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W4VR on August 6, 2007 Mail this to a friend!
I don't believe there is a single switching power supply out there that generates noise you won't hear in your HF radio. I have an Astron switching supply and there is also one in the Icom PW1. I've noticed these weak rough-sounding whistles scattered throughout the upper HF bands...when I turn off the PW1 they go away. I'm not sure if they are radiated or conducted emissions, but I do know that the PW1 power cord has 3 ferrite toroids where it exits the amplifier. In the majority of the cases the noise is blanketed by normal band noise so it's not a big deal.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W6TH on August 6, 2007 Mail this to a friend!
.
Some of these small transformers that are in use today, are of the switching variety.

Hmmm I'm wondering if the 21st. century advances are all they are cracked up to be?

Hmmm, me too/also.

.:
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by N3JBH on August 6, 2007 Mail this to a friend!
KE3WD "Can't find George Bush's callsign in the QRZ database.
So how exactly does mentioning him relate to Ham Radio again?"

Funny i found 4 listings for Goerge Bush :)


KE6PXP
N2JJE
N4OQO
WT9Z

Sorry Mac could not resist it

Jeff
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by N3JBH on August 6, 2007 Mail this to a friend!
dang typo's
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KE3WD on August 6, 2007 Mail this to a friend!
Funny, Jeff.

>>>by N2RRA on August 6, 2007 Mail this to a friend!
Great article!

Maybe you guys can help with this problem.

Not getting any noise from the P.C. or transformer itself, but from the monitor.

Only when I turn the monitor "On" is when I get warble type sound till it spike's 5-9+. Turn the VFO will get rid of it till it catch's up again.

What is this?
How do I get rid of it? <<<

Sounds like AC Ground Loop in the audio connection to the soundcard.

Use of audio isolation transformer(s) between rig and soundcard will likely eliminate this.


.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W4LGH on August 6, 2007 Mail this to a friend!
"Only when I turn the monitor "On" is when I get warble type sound till it spike's 5-9+. Turn the VFO will get rid of it till it catch's up again."


Try switching video resolutions, also check the Vertical frequencies, most can select 60/75 & 85hz.
Try all 3 and see what happens. If none of that works, go with a flat panel screen...

73 de W4LGH - ALan
http://www.w4lgh.com

 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by K9MI on August 6, 2007 Mail this to a friend!
Exactly. The guys who have their antennas away from the shack by a great deal won't get this, or the birdies from CRT monitors, that we poor folk on small lots (50x130) get. I guess I could always ask the neighbors about using their yards for installing a tower. ;-)

K9MI
 
RFI Noise and Inexpensive Computer Power Supplies  
by K9MI on August 6, 2007 Mail this to a friend!
LCD monitors, at least the one I have, does well in eliminating birdies I'd get from my 17" crt's.

k9mi
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W4LGH on August 7, 2007 Mail this to a friend!
LCD monitors still use the same HORIZ and VERT osc. but they do not have to generate the high voltage associated with a CRT. This helps a great deal with reducing the amount of radiation, thus the noise you pick up in your radio. Also the LCD displays are much better shielded, since there is no Hi-Voltage.

My last CRT would tear 18.130 up, but the flat screen cured that. There are many other benefits gained by going to LCD panels too. My biggest one was getting it off my radio table and mounted it on the wall with a swivel mount. The prices have become more than affordable now, and you can catch them on sale for less than a $100! Once you switch over, you'll wonder why it took you so long!

73 de W4LGH - Alan
http://www.w4lgh.com
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by N2RRA on August 7, 2007 Mail this to a friend!
Thanks Alan and guy's

I'll try what you suggested with the Resolution and stuff. Thing is I have a LCD flat screen 19", but probably date's back about 6yrs. old now.

Maybe better shielding in production happened not to long ago.


Thanks!
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KE3WD on August 7, 2007 Mail this to a friend!
>>I'll try what you suggested with the Resolution and stuff. Thing is I have a LCD flat screen 19", but probably date's back about 6yrs. old now<<

You might try adding clampon ferrite suppressors to the video and power cables. The video cable likely has one on it, another couldn't hurt. Might help a lot, might not, only way to find out is to try.


.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by AC7ZL on August 7, 2007 Mail this to a friend!
KE3WD said on August 6, 2007

>Would anybody who makes reference to the ages old
>IRS refund check as being, "George Bush's check"
>be likely to be the same kind of person who would not
>do their homework regarding the PSU for the shack
>puter and go with a thirty dollar case?
>
>The lost art of critical thinking.
>
>And then write an article about

It is obvious to me that the author used the phrase "George Bush's check" tongue-in-cheek.

I would agree that there is ample evidence of the general public's loss of the ability to think critically.

On the other hand, it is equally apparent to me that an awful lot of people seem to have lost their sense of humor.

I guess that once a president has "stolen" two elections, caused the 9/11 attacks and global warming, started a war we didn't need, flooded New Orleans on purpose, triggered the collapse of the bridge in Minnesota and the mine disaster in Utah, (not to mention causing the fuzzy picture on my television and the rod-knock in my neighbor's car) you can't mention his name any more---even in jest.

Pete
AC7ZL

 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W6TH on August 7, 2007 Mail this to a friend!
.

{I guess that once a president has "stolen" two elections}.
..................................................

Well to be sure there wasn't much of a choice to elect between John Kerry and George Bush.

Both are aristocrats, and war mongers, both would do the same and commit our boys to an Unconditional war in Iraq.

Bush lied as to weapons of mass destruction as there was never a threat from Iraq towards the United States of America.

Also Bush took the oath of office under the conditions he would follow the Constitution of These United States of America and its Bill of Rights.

Did Bush follow our law of the land? Certainly did not and put our country into one hell of a mess, all those poor Iraqi men, women and children and yes and our American boys in service being killed.

I won't mention how our cost of living has gone up, sure Bush had nothing to do with that.

Bush isn't the loser, we Americans are.

.:

 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by W5GA on August 7, 2007 Mail this to a friend!
Can we get off the political soapboxes now, and get back to radio? I'm more political than most, but guys, this ain't the place for it!!!
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KF4KQI on August 7, 2007 Mail this to a friend!
I've always used Forton power supplies. They are built like tanks, and are about as heavy, and they are a good price.

I have zero noise from three computers in my house with them.
 
RFI Noise and Inexpensive Computer Power Supplies  
by K1CJS on August 7, 2007 Mail this to a friend!
You get what you pay for. Pay less get cheap crap.

I've built a half dozen computers for use in my shack--and in others shacks too--and not one of them put out any noticeable noise. Not one. I used Astron supplies in all of them. You pay more but it certainly is worth it.

Now, if you want a knock around computer for the kids college dorm, cheap is probably the way to go....
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by K1CJS on August 7, 2007 Mail this to a friend!
"Did Bush follow our law of the land? Certainly did not and put our country into one hell of a mess, all those poor Iraqi men, women and children and yes and our American boys in service being killed."

So, is that why the idiots in Congress won't impeach him, because Kerry would have done the same? Well, he didn't have the chance, did he?

"I won't mention how our cost of living has gone up, sure Bush had nothing to do with that."

Yep--you're right--that started to skyrocket because of Reagan and GW's father.

"Bush isn't the loser, we Americans are."

No, I think Bush IS the loser, and we're the suckers that made sure he stayed where he could do the most harm--which MADE us losers.

Thank you---now back to the ham site for more half truths and utter nonsense.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by STRAIGHTKEY on August 8, 2007 Mail this to a friend!
Those weren't George Bush's checks, he just "liberated" the money and it's a personal "freedom fund".

We should be getting another check this year with all the money we're saving by not going through court orders for wiretaps....ooooops, wait, I forgot about Iraq. Nevermind.

But back on topic, I had the same problem with a power supply. I took care of it by yanking it out and throwing in a different power supply. These things are so cheap, it's not worth the time and effort fixing them. The old supply became junk box parts.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by KE7IPY on August 9, 2007 Mail this to a friend!
A couple months ago I noticed a lot of interference and assumed it was from the new window box air conditioner I put in. I was packing up for my annual trip to Maui, and had the air con off, but the interference was still there. As I was unplugging my accessories, as soon as I unplugged this chintzy USB power adapter (it's a 5v, 500mAmp power supply with a USB plug in it) the interference disappeared. I fired up the AC, and sure enough, it was clean. All this RFI was caused by a $5 discount power adapter I used for my Ipod. Caveat Emptor.
 
RE: RFI Noise and Inexpensive Computer Power Suppl  
by N4MJG on August 14, 2007 Mail this to a friend!
no problem here and no i can't tell you how i did mine when i built it lol.



73
Jackie
KG4ORX
WEBSITE http://webpages.charter.net/kg4orx/
 
RFI Noise and Inexpensive Computer Power Supplies  
by KF6ZZ on August 22, 2007 Mail this to a friend!
Since the PS manufacturer omitted the RF filtering components to cut costs, it is likely that they also
undersized critical components just to save pennies.

IOW, you probably have a power supply with:
overstressed rectifiers,
overstressed resistors,
overstressed switching transistors
undersized heatsinks....etc.

After a coupla hundred hours operation,
take the cover off
the PS and look for burned spots
on the circuit board.

A real eye opener !!

A few years ago, I had an ATX PS failure wherein
all the output voltages doubled !
... and toasted the motherboard, C drive, D drive
CD burner, and so on.

It was caused by a 1/8 watt resistor
dissipating 1 watt of heat !

The power supply was still functional
( albiet out of spec !)
after it had destroyed my computer.

Further investigation revealed that
most of the critical PS
components were way too small.

Missing RFI filters are indicitive of
low-quality build throughout the PS.

You will have to spend about a "C-note"
to get a quality ATX PS.

- KF6ZZ
 
RFI Noise and Inexpensive Computer Power Supplies  
by NF4P on August 23, 2007 Mail this to a friend!
Radio works sells an inexpensive RFI filter called a TG4 works very well if instructions are followed
 
Email Subscription
You are not subscribed to discussions on this article.

Subscribe!
My Subscriptions
Subscriptions Help

Other How To Articles
Nice Looking Mic for Shack