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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The company I work for (Eaton –
Cutler-Hammer) uses PWM in AC VF drives to control the speed of AC motors.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>73,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Marsh, KA5M<o:p></o:p></span></font></p>
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10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
lcc-bounces@louisianacontestclub.org
[mailto:lcc-bounces@louisianacontestclub.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Dan Edward Dba East edwards<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, August 02, 2010 2:57
PM<br>
<b><span style='font-weight:bold'>To:</span></b> Randy Prewitt<br>
<b><span style='font-weight:bold'>Cc:</span></b> lcc@louisianacontestclub.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [LCC] RFI problem
from our <st1:State w:st="on"><st1:place w:st="on">Texas</st1:place></st1:State>
connection</span></font><o:p></o:p></p>
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12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>hey randy<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>thats interesting. i thought PWM's (pulse width
modulation) were just used for <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> <st1:State w:st="on">d.c.</st1:State>
motors....they're putting <st1:State w:st="on"><st1:place w:st="on">d.c.</st1:place></st1:State>
motors in washing machines now ??<o:p></o:p></span></font></p>
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style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>they ( pwm's ) DO make a nasty looking square wave,
which contain many<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>many many frequencies...<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>curious......or maybe i'm just stupid and dont know
about PWM's & ac motors...<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>73, w5xz, dan<o:p></o:p></span></font></p>
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style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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style='font-size:12.0pt'><br>
<br>
--- On <b><span style='font-weight:bold'>Mon, 8/2/10, Randy Prewitt <i><span
style='font-style:italic'><ranprew@foxsale.com></span></i></span></b>
wrote:<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
From: Randy Prewitt <ranprew@foxsale.com><br>
Subject: [LCC] RFI problem from our <st1:State w:st="on"><st1:place w:st="on">Texas</st1:place></st1:State>
connection<br>
To: lcc@louisianacontestclub.org<br>
Date: Monday, August 2, 2010, 7:14 AM<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Forwarded from our <st1:State
w:st="on"><st1:place w:st="on">Texas</st1:place></st1:State> friends. Two
separate exchanges.<br>
<br>
randy K4LJA in <st1:place w:st="on"><st1:City w:st="on">Monroe</st1:City>,
<st1:State w:st="on">LA</st1:State></st1:place><br>
<br>
----- Original Message ----- Sent: Sunday, August 01, 2010 9:16 PM<br>
Subject: Re: FW: RFI problem<br>
<br>
<br>
> I also monitor the RFI reflector and that sounds correct to me. If
your rfi is low level or can be worked around count yourself lucky. I
would think your machine would have a low usage. It will be interesting
to hear what Whirlpool has to say. I've worked with Mike Gruber
at ARRL when I was involved with Vectren Energy. Good man.....<br>
> <br>
> Skip<br>
> <br>
> On 8/1/2010 20:45, Randy Farmer wrote:<br>
>> <br>
>>> I contacted ARRL about my washing machine RFI problem and
received the following response. My RFI isn't all that bad, so I'm not
sure I'm going to do all of this stuff, but I thought it might be of interest
to some of you.<br>
>> <br>
>> I'm subscribed to the RFI reflector, and there have been numerous
messages regarding washing machine RFI complaints. Most the newer "high
efficiency" models use DC motors with variable speed controls. The designers
know how to make PWM motor controls cheap, but they don't know squat about
EMI. The haphazard wiring, with no common ground point (if there's one at
all) make them dandy radiators. Seems that one of the Korean brands, maybe
Samsung or LG, has a reputation of being pretty clean. Whirlpool is reputed
to be the worst.<br>
>> <br>
>> As I recall, the consensus of the experts on the RFI reflector is
that the FCC doesn't regulate "appliances" at all. If they don't
now, they're not likely to start any time soon. Welcome to the 21st century.<br>
>> <br>
>> 73...<br>
>> Randy, W8FN<br>
<br>
<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><br>
No virus found in this outgoing message.<br>
Checked by AVG - www.avg.com<br>
Version: 8.5.441 / Virus Database: 271.1.1/3043 - Release Date: 08/01/10
06:34:00<o:p></o:p></span></font></p>
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