[LCC] RFI problem from our Texas connection

Fri Aug 6 10:10:11 EDT 2010

good to know...i learn something new almost every day, when i'm paying attention....even though i KNOW i'm getting dumber by the minute..
must be cheaper, or more efficient, or both, than just varying voltage ? 
73, w5xz, dan

--- On Thu, 8/5/10, Marshall Stewart <marsh at ka5m.net> wrote:

From: Marshall Stewart <marsh at ka5m.net>
Subject: RE: [LCC] RFI problem from our Texas connection
To: "'Dan Edward Dba East edwards'" <dan.n.edwards at sbcglobal.net>, "'Randy Prewitt'" <ranprew at foxsale.com>
Cc: lcc at louisianacontestclub.org
Date: Thursday, August 5, 2010, 3:54 PM

The company I work for (Eaton –
Cutler-Hammer) uses PWM in AC VF drives to control the speed of AC motors. 

73, 

Marsh, KA5M 

From:
lcc-bounces at louisianacontestclub.org
[mailto:lcc-bounces at louisianacontestclub.org] On
Behalf Of Dan Edward Dba East edwards

Sent: Monday, August 02, 2010 2:57
PM

To: Randy Prewitt

Cc: lcc at louisianacontestclub.org

Subject: Re: [LCC] RFI problem
from our Texas 
connection 

  hey randy 

  thats interesting. i thought PWM's (pulse width
  modulation) were just used for  

    d.c. 
  motors....they're putting d.c. 
  motors in washing machines now ?? 

  they ( pwm's ) DO make a nasty looking square wave,
  which contain many 

  many many frequencies... 

  curious......or maybe i'm just stupid and dont know
  about PWM's & ac motors... 

  73, w5xz, dan 

  --- On Mon, 8/2/10, Randy Prewitt <ranprew at foxsale.com>
  wrote: 

  From: Randy Prewitt <ranprew at foxsale.com>

  Subject: [LCC] RFI problem from our Texas 
  connection

  To: lcc at louisianacontestclub.org

  Date: Monday, August 2, 2010, 7:14 AM 

  Forwarded from our
 Texas friends. Two
  separate exchanges.

  randy  K4LJA in Monroe ,
   LA

  ----- Original Message ----- Sent: Sunday, August 01, 2010 9:16 PM

  Subject: Re: FW: RFI problem

  > 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.....

  > 

  > Skip

  > 

  > On 8/1/2010 20:45, Randy Farmer wrote:

  >> 

  >>> 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.

  >> 

  >> 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.

  >> 

  >> 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.

  >> 

  >> 73...

  >> Randy, W8FN

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