The following website has a 1M .mp3 file of some QRM
I'm getting on 160 meters. A little background is in order:

My station has my PC about 3' away from my FT-857D's.
I've eliminated all cables except video so I'm pretty sure it's
not coming from them. I've powered off my monitor and
adjusted the refresh rate to no avail. I grounded the PC's
metal case and tried it with/without the side covers. No
difference in the signal.

Tonight I looked at my CPU temp and it was a tad higher
(127 deg F) than normal so I decided to turn on a box
fan pointed at the left side of the tower case. To my shock,
the QRM faded away! I switched the fan on and off several
times to prove my theroy. Then I made the mp3 recording you
can download he

http://members.cox.net/kg0wx/index.html

Listen closely to the sound - at 2.2 seconds into the rec-
ording, you can hear the "tick" that is me turning on the
fan to "low". Within a few seconds, the QRM is gone!

Anybody know where I should look to find this and kill
it?

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

On Thu, 17 Mar 2005 23:04:09 -0600, "Ken Bessler"
wrote:
Tonight I looked at my CPU temp and it was a tad higher
(127 deg F) than normal so I decided to turn on a box
fan pointed at the left side of the tower case. To my shock,
the QRM faded away! I switched the fan on and off several
times to prove my theroy.

Hi Ken,

You convinced me - CPU.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Thu, 17 Mar 2005 23:04:09 -0600, "Ken Bessler"
wrote:
Tonight I looked at my CPU temp and it was a tad higher
(127 deg F) than normal so I decided to turn on a box
fan pointed at the left side of the tower case. To my shock,
the QRM faded away! I switched the fan on and off several
times to prove my theroy.

Hi Ken,

You convinced me - CPU.

73's
Richard Clark, KB7QHC

I would think that the likely suspect would be one that does
not already have a fan. I followed the signal as it went off
freq and faded. It climbed 3 kc on 40m then faded out.

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

On Fri, 18 Mar 2005 10:27:36 -0600, "Ken Bessler"
wrote:

On Thu, 17 Mar 2005 23:04:09 -0600, "Ken Bessler"
wrote:
Tonight I looked at my CPU temp and it was a tad higher
(127 deg F) than normal so I decided to turn on a box
fan pointed at the left side of the tower case. To my shock,
the QRM faded away! I switched the fan on and off several
times to prove my theroy.

I would think that the likely suspect would be one that does
not already have a fan. I followed the signal as it went off
freq and faded. It climbed 3 kc on 40m then faded out.

Hi Ken,

I don't quite follow the implication of your statement. Do you have a
dual CPU system, where one CPU has a fan and the other not?

As it appears to be temperature based (the reason why the fan appears
to be significant) and CPU based (over clocked for its operating
temperature); I would suggest trying to cool the CPU with an aerosol
(freeze mist) or one of those cans of air for keyboard cleaning.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
. . .
As it appears to be temperature based (the reason why the fan appears
to be significant) and CPU based (over clocked for its operating
temperature); I would suggest trying to cool the CPU with an aerosol
(freeze mist) or one of those cans of air for keyboard cleaning.

You can use the "canned air" as a freeze mist ("spray cold"), or
vice-versa, by inverting the can while you spray. They contain
essentially the same stuff, the difference being that the "spray cold"
contains a syphon tube to suck liquid up while the "canned air" doesn't.

Roy Lewallen, W7EL

In article djt_d.14823$Fy.7702@okepread04,
Ken Bessler wrote:

Tonight I looked at my CPU temp and it was a tad higher
(127 deg F) than normal so I decided to turn on a box
fan pointed at the left side of the tower case. To my shock,
the QRM faded away! I switched the fan on and off several
times to prove my theroy. Then I made the mp3 recording you
can download he

http://members.cox.net/kg0wx/index.html

Listen closely to the sound - at 2.2 seconds into the rec-
ording, you can hear the "tick" that is me turning on the
fan to "low". Within a few seconds, the QRM is gone!

Anybody know where I should look to find this and kill
it?

Most modern PCs use a multi-stage power regulation system. The main
power supply isolates and steps down the mains power to create several
DC voltages (+5 and +12 in particular) which are routed to the
motherboard. Then, an on-board regulator further reduces the voltage
being fed to the CPU to meet the CPU's requirements.

Modern CPUs such as the Intel P4 family and the AMD Athlon consume a
large amount of current (tens of amperes) at low voltage (1.2 - 1.8
volts, roughly speaking). Modern AGP graphics cards also operate on
low voltages (AGP 4x is 1.5 volts, AGP 8x is 0.8 volts if I remember
correctly) at high amperages.

To create such high currents at such low voltages in an efficient
manner, single- or multi-phase "bucking" voltage regulators are used.
These are switching regulators, which step down the main voltage (most
commonly from the +12 supply) and step up the amperage. They
typically operate at switching frequencies ranging from the high tens
of kHz up to the low MHz range.

I suspect that the QRM you are hearing is from the fundamental or
harmonic of one of these switching-regulator oscillator rates.
Heating and cooling of the CPU and motherboard are probably causing
the switching oscillator to drift a bit.

As to how to get rid of it... you're already on the right track, I
think... shielding and filtering. Make sure that your monitor and
power (and other) cables have ferrites on them, as close as possible
to the PC case. Make sure you've got a "tight" PC chassis, with metal
shielding in every possible location (including screw-secured plates
over any unused PCI slots, snap-in metal shields for any unused
hard-drive bays, etc.). I recommend a chassis which is actually all
metal, rather than one of the new lighter-weight plastic chassis with
an anti-EMI coating on the inside. Don't run your PC with the side
panels off - put 'em on and fasten the screws.

As for the gamer-style transparent acrylic PC chassis, forget 'em - I
have serious doubts as to whether a PC build in one of these can pass
the FCC Part 15 tests, let alone be RF-clean enough to use in a ham
shack.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Dave Platt" wrote in message
...
In article djt_d.14823$Fy.7702@okepread04,

snip

I suspect that the QRM you are hearing is from the fundamental or
harmonic of one of these switching-regulator oscillator rates.
Heating and cooling of the CPU and motherboard are probably causing
the switching oscillator to drift a bit.

As to how to get rid of it... you're already on the right track, I
think... shielding and filtering. Make sure that your monitor and
power (and other) cables have ferrites on them, as close as possible
to the PC case. Make sure you've got a "tight" PC chassis, with metal
shielding in every possible location (including screw-secured plates
over any unused PCI slots, snap-in metal shields for any unused
hard-drive bays, etc.). I recommend a chassis which is actually all
metal, rather than one of the new lighter-weight plastic chassis with
an anti-EMI coating on the inside. Don't run your PC with the side
panels off - put 'em on and fasten the screws.

As for the gamer-style transparent acrylic PC chassis, forget 'em - I
have serious doubts as to whether a PC build in one of these can pass
the FCC Part 15 tests, let alone be RF-clean enough to use in a ham
shack.

--
Dave Platt

I've already buttoned up the all metal case with grounded side covers.
I even made sure (with a DVM) they were grounded. (The ends of the
mini tower are metal with the front having a plastic facia on top of the
metal case front).

No help. The only thing that helped was taking both covers off and
blowing air through the chassis. I monitor 3 temps - CPU, Motherboard
and power supply exhaust air. Before the box fan, I was running CPU
at 129-140, Motherboard at 100-118 and power supply exhaust at
room temp +16 degrees (F).

Now I've got CPU at 113, MB at 93 and exhaust at room + 8 deg.

I was planning on buying a can of air and further investigating this but
I feel I've solved it with the box fan. The interference is gone and my
PC is cooler.

Thanks for the ideas!
--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

My new plastic sided (gamer?) 2.8 GHz PC causes not a single problem here in
the shack. My older 400 MHz Celeron however totally trashes 80 meters and is
only tolerable on 40 meters, everything else is fine. Go figure.

Sam

Ken Bessler wrote:
The following website has a 1M .mp3 file of some QRM
I'm getting on 160 meters. A little background is in order:

My station has my PC about 3' away from my FT-857D's.
I've eliminated all cables except video so I'm pretty sure it's
not coming from them. I've powered off my monitor and
adjusted the refresh rate to no avail. I grounded the PC's
metal case and tried it with/without the side covers. No
difference in the signal.

Tonight I looked at my CPU temp and it was a tad higher
(127 deg F) than normal so I decided to turn on a box
fan pointed at the left side of the tower case. To my shock,
the QRM faded away! I switched the fan on and off several
times to prove my theroy. Then I made the mp3 recording you
can download he

http://members.cox.net/kg0wx/index.html

Listen closely to the sound - at 2.2 seconds into the rec-
ording, you can hear the "tick" that is me turning on the
fan to "low". Within a few seconds, the QRM is gone!

Anybody know where I should look to find this and kill
it?

I had a similar problem with a new computer system I recently built up.
Problem was a noisy 350W Power Supply.

I replaced it and the machine now is perfectly quiet. A good solution
for a few bucks. It is very hard to shield a computer from this sort of
noise as it radiates from the leads in addition to directly from the case

Dick K7RNZ