Re: [linrad] Buying the Linux PC for Linrad use.

[David Garnier <dgarnier@xxxxxxxxx>]

Jim & All,

I work for a major medical electronics company in the midwest,
I do EMC test & certification and I have some experiance on
certifing PC based products.  My last product met Group 1
Class A - IEC61000-1-2 Revison 2.

We ended up selecting an Intel P4 CPU and Intel P4 mother
board for a couple of reasons.  1) The P4 processor has a better
overtemp solution (if the heatsink pops off) than comparable
AMD cpu's do.  Our product can be rolled around anywhere
in or outside a hospital. It has to be reliable and survive bumps
and elevator thresholds and the like. Boxed Processors come
with a fan and as a package are garanteed for 3 years, (think
about this.) 2) Intel claims their motherboards are tested to
comply with FCC Home & Office use Class B radiated
emissions specs.  3)  FCC Home & Offices specifies that
radiated emissions testing to be done WITH the PC cabinet's
cover OFF.  I did such "cover off testing" to our 845GBV Intel
board & 2 Ghz P4 processor, from 30 Mhz to 6.5 Ghz their
were under the Group 1 Class B limit!  4) I did comparaible
radiated emission testing to a P4 based MSI motherboard and
they did not fare as well as the 845GBV. 5) Intel assembly
notes (for PC assemblers) states "to meet radiated emission
compliance must use their supplied I/O shield cutout to pass.
6) My take away (for this testing) is that Intel manufactured
motherboards are a excellent choice for being radiated emission
quiet.  7) Since my testing I have upgraded 3 of my home PC's
to Intel motherboards, that's what I use.

Trying to purchase a FCC compliant PC cabinet & supply
for home use has not been so easy.  I purchased 3 PC boxes
at Dayton, clearly marked as being "FCC Class B compliant,"
they are not.  I would go as far as stating this practice as
fraudulant.  From past experiance I have found that the power
supply vendor cut corners by de-populating the power supply's
the AC line filtering componets (pi-network caps & chokes)
and adding wire jumpers in their place.  I discovered this
problem when 20 meters suddenly had a S15 noise floor. The
solution was to replace these wire jumpers with simular filter
componets from dead donor supplies.

If all else fails add ferrite beads to every cable and copper tape
ever seam or orfice.  Remove items one at a time until the RFI
appears again. (Copper Tape is the EMC version of duck tape.)

If you are going to purchase a PC, make sure the compliance
label on the box says it's "tested to comply with FCC home or
office use" run away from PC clones that are labled "assembled
from FCC tested componets."  As we say in the EMC business,
CE+CE does not equal CE.

I have some application notes and RFI gasketing suggestings I
can send to you or others on this subject.  73's & GL.

Dave Garnier - wb9own

wb9uwa@xxxxxxxxxxx wrote:

> Hi All,
> >... I am looking at
> >the most basic AMD option. Before I order this PC, is there anything I should
> >be careful of or perhaps specify a different option? I am concerned that
> >I can not test the PC for RF emissions before I buy it. Perhaps there is a
> >better case that I should select?
>
> http://www.pcusa.com/
>
> Home Series: AMD Duron / Athlon / XP DDR System
>
> Home Series: AMD Duron / Athlon / XP DDR System Configurator : Standard with all ports : 1
> serial, 1 printer, 2 USB Ports.
>   Current Price: $275
> AMD XP 1800+  1.53 ghz 266 fsb
> 266mhz fsb pc chips 810d sis730d w/video, audio, lan
> 256mb ddr / 266 MHZ ram
> Maxtor 20gb 7200 rpm
> 52x cd rom internal, IDE
> video 32mb max 3d svga share
> Specs are available on site.
>
> 73, Jim Shaffer, WB9UWA.


LINRADDARNIL