K7S5A radio noise

I put together a $90 Fry's special K7S5A/Athlon 2400+ last week. I used
a $28 case with a 450 watt PS I bought at at the TRW ham radio swap
meet. I put in 256MB of PC2100 for $26.

The system booted right up and runs great, but I get a lot of noise on
the radio. My other systems
are based on FIC 503+ and Abit BX6 motherboards with K6-III+ and PIII
cpus and they
don't generate much radio noise.

Is it the cpu, the motherboard or the power supply that generates all
the noise?
What can be done to reduce the noise?

My radio is an ICOM 735 ham radio connected to a 5 band trapped vertical
antenna
mounted outside on the roof. I listen to a lot of AM commercial radio on
this system
and some ot fhe lower powered local stations get wiped out when I turn
on the K7S5A
system.

On Tue, 08 Jul 2003 21:47:45 GMT, Jam <> wrote:

>I put together a $90 Fry's special K7S5A/Athlon 2400+ last week. I used
>a $28 case with a 450 watt PS I bought at at the TRW ham radio swap
>meet. I put in 256MB of PC2100 for $26.
>
>The system booted right up and runs great, but I get a lot of noise on
>the radio. My other systems
>are based on FIC 503+ and Abit BX6 motherboards with K6-III+ and PIII
>cpus and they
>don't generate much radio noise.
>
>Is it the cpu, the motherboard or the power supply that generates all
>the noise?
>What can be done to reduce the noise?
>
>My radio is an ICOM 735 ham radio connected to a 5 band trapped vertical
>antenna
>mounted outside on the roof. I listen to a lot of AM commercial radio on
>this system
>and some ot fhe lower powered local stations get wiped out when I turn
>on the K7S5A
>system.
>


I would guess that your power supply is radiating rf. I had to change
out 3 supplies here to eliminate am interference. 2, K7S5A and an old
pentium at box. I also have a 503+ that generates vhf spurs that stop
the scanners around 155MHZ. That is a mb problem.

Steve N2PTJ

Television Service Center
Steve Tomaszewski N2PTJ
6 North Hill Dr
Ballston Lake, NY 12019
518-877-6665

On Tue, 08 Jul 2003 21:47:45 +0000, Jam wrote:


> Is it the cpu, the motherboard or the power supply that generates all
> the noise?
> What can be done to reduce the noise?

I have a K7S5A/Athlon XP2100+ running in my radio shack.
I'm happy to report that it makes no RF noises on any
band from 160M up to 2M.

If you have a well screened metal case, most of the
interference is probably radiated by one or more of
the various wires coming from the back of the case.
Try disconnecting all peripheral devices one at a time.
The monitor is a likely source of RF interference. Remove
the mouse, ethernet cables, telephone line, even the
keyboard if the machine will boot without it. If all
of this fails to improve the situation, the noise is
probably from the PSU. Try some large clamp-on ferrite
cores on the mains supply lead. Put them as close to
the case as possible. It is relatively easy to filter
out noise on the higher frequency bands, but it can be
quite tricky to get rid of interference on MW or LW.

Your trapped vertical may share a common ground connection
with your PC. Try using different mains sockets for the
radio and PC. Try using a mains lead with a built-in
RFI filter.

Good Luck.

73, Ed. EI9GQ.


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On Tue, 08 Jul 2003 21:47:45 GMT, Jam <> wrote:

>I put together a $90 Fry's special K7S5A/Athlon 2400+ last week. I used
>a $28 case with a 450 watt PS I bought at at the TRW ham radio swap
>meet. I put in 256MB of PC2100 for $26.
>
>The system booted right up and runs great, but I get a lot of noise on
>the radio. My other systems
>are based on FIC 503+ and Abit BX6 motherboards with K6-III+ and PIII
>cpus and they
>don't generate much radio noise.
>
>Is it the cpu, the motherboard or the power supply that generates all
>the noise?
>What can be done to reduce the noise?
>
>My radio is an ICOM 735 ham radio connected to a 5 band trapped vertical
>antenna
>mounted outside on the roof. I listen to a lot of AM commercial radio on
>this system
>and some ot fhe lower powered local stations get wiped out when I turn
>on the K7S5A
>system.
>

Time to swap out stuff or use a portable radio and stick it next to
everything. Then start filtering.