[RFI] Noisy or Quiet Power Supplies?

[Dale Svetanoff]

Doc,

I don't know about that particular switching power supply, but I do know
that I have done a lot of business over the past 10+ years with MCM, and I
have found them very good to deal with.  Unless someone specifically tells
you that the unit is a "screamer", I'd suggest asking the person who takes
your phone order if you can return it for RFI reasons.  I will guess that
they will allow that.  It can't hurt to ask.

I have been running the Astron SS-30M for several years now with NO
problems whatever.  (See QST back in 2002 - can't recall the issue -  for a
review of the Astron, and other, switching power supplies.  The ARRL did an
excellent job of testing several popular models - most of which are still
available.  Read the reviews then buy.  That's why I bought the Astron; it
was the lowest noise unit they tested.)

A reminder:  although keeping conducted emissions to a low level on the DC
output lines is important for minimizing noise coupling from a switcher
supply into the equipment it is powering, it is also important to be
certain that you do not have any antennas located real close to the shack
that could pick up radiated emissions from the DC cables or the cabinet of
the power supply itself.  My HF antennas at the home QTH are more than 50
feet away from the shack, and all point away from the shack.  I have used
the Astron on Field Day with HF antennas strung overhead and not had
problems, so I do think it is a truly excellent unit.  (No, I have no
vested interest in Astron, but as an EMC engineer, I can tell good design
when I see it.  Astron does not spare the ferrites in their SS-series of
power supplies.)

I do own several pieces of Tenma test equipment.  It all works OK, but none
of what I have is a switcher.

73, Dale
WA9ENA  


> [Original Message]
> From: doc at kd4e.com <doc at kd4e.com>
> To: <undisclosed-recipients:>
> Date: 10/16/2010 10:47:49
> Subject: [RFI] Noisy or Quiet Power Supplies?
>
> Anyone know if these things are RFI-quiet enough to be around
> a Ham shack?
>
> Tenma Heavy Duty 40 Amp Switch Mode Power Supply
> 72-7665 (727665) | MCM-Tenma  Sale:  $99.
>
> http://www.mcmelectronics.com/product/72-7665
>
> -- 
>
> Thanks!&  73, doc, KD4E
> http://KD4E.com
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