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Re: [RFI] EMI & EMC Conducted Noise Meaning?

To: kd4e@verizon.net
Subject: Re: [RFI] EMI & EMC Conducted Noise Meaning?
From: <dgsvetan@rockwellcollins.com>
Date: Mon, 9 Jan 2006 13:49:45 -0600
List-post: <mailto:rfi@contesting.com>

There are some very significant differences between CL A and CL B devices
in the EMC world.  If you really do intend to use radios while this thing
is running, and also if the antennas for those radios are fairly close to
(or on) your house, then the alternative you present below is not a bad
idea.  Another approach would be to find a linear power supply (they do
show up at the surplus dealers) with appropriate output power.  If it hurts
your back to lift it, it's a linear supply!

I have seen similar postings from other list users on using industrial or
computer power supplies for various applications in and around the shack.
I refer you to the excellent product reviews of radio-application power
supplies in the January, 2000, issue of QST.  Basically, if the power
supply you intend to use doesn't have performance similar to those tested,
I would not recommend use in or around the shack.  This is especially true
if your antennas are close to the shack.  (Think about it; your rigs are
usually encased in metal, with shielded coax for connection to the
antennas, and it is powered by a power supply that provides some isolation
from AC power line conducted noise.  However, a piece of industrial
equipment, sitting in the open or having only a partial enclosure, can
radiate right through the non-shielded roof and walls of your house and
couple into the antennas if they are nearby.  The electrical noise from the
industrial equipment can also get onto the AC power wires of your house and
then you have nice large area radiators to couple into your antennas.)

One thing about your battery plan - it won't conduct on the AC power
wiring.  Best luck.

73, Dale

             >                                                          To 
             Sent by:                  rfi@contesting.com                  
             rfi-bounces@conte                                          cc 
                                       Re: [RFI] EMI & EMC Conducted Noise 
             01/06/2006 09:38          Meaning?                            
             Please respond to                                             

I think I will go back to the original plan.

Start with a pair of 12v batteries in series and drop the
voltage to 19 and 16 v using a couple of zeners, some
resistors, and regulators.

I am guessing that is the most bulletproof and least
noisy methodology.

The key will be to keep the voltage level up in the batteries
so the linear relationship between the source and the output
will be maintained.

That will require batteries with significantly more capacity
than I anticipate needing and redundant recharging sources:
solar, ac, and perhaps a pedal-driven generator!

I wonder if a big fat cap, perhaps one of the auto sound
1 farad jobs, on each output will absorb the load surges
and keep everything happier?

> I doubt the power supply you are talking about can be as quiet as you
> it to be.  For one thing it really is an "industrial" supply. No one is
> ever likely to be listening to a Braves game on the AM radio next to one,

> you know? So they don't have to design it so anyone can.  And it's a high
> powered supply, too, which implies minimal impedance (RF filtering) on
> supply and output sides.
> Per your separate E-mail I see you want to run laptop computers off quiet
> PS's.   I am looking myself at modifying an analog 13.8V PS to 16V for a
> laptop computer, to get rid of the noise a switcher makes.  It's no big
> deal (assuming the caps can handle 16 volts) to move a 13.8V PS up to 16
> volts. or to add a separate 16 volt regulator (if there's enough voltage
> for it).   19 volts is a bit different story and you might may have to
> build an analog PS or start with a 24V (analog!) one just for that.
> Switchers *can* be quiet,, but in general, for Amateur Radio use,  if you
> do get a switching PS -- they're light, small and efficient -- you'll
> one that has been >tested< as quiet. And not just Class B quiet, either,
> but quiet in actual use.

A blessed New Year to all!
Thanks! & 73, doc kd4e

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