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<DIV>A switching PS converts the AC to high voltage DC, then uses a square wave
oscillator to feed a step-down transformer. The output is rectified back to DC.
The oscillator typically runs at 100Khz or so creating lots of RF
noise. Running at high frequency allows for a much smaller transformer,
uses less metal, is lighter. The filter capacitors at the DC output can be
smaller as well. Using square waves make the PS more efficient,
converts more of the energy to power instead of heat. The on-off cycle of the
square wave is adjusted to regulate the output voltage. For a more technical
explanation, there's always Google.</DIV>
<DIV> </DIV>
<DIV>Unless you are well-versed in electronics, forget about attempting to
tame the noise. Buy a switcher that as part of its description says little
or no RF noise is generated. Astron makes a bunch. </DIV>
<DIV> </DIV>
<DIV>BTW, the Apple II computer from bygone days was the forerunner of PCs and
other gadgets using switchers. Kudos to Steve Jobs, the guy was eccentric but
brilliant. </DIV>
<DIV> </DIV>
<DIV>Chris, KL7DM</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 11/2/2015 5:47:56 P.M. Pacific Standard Time,
kd6edv@gmail.com writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" color=#000000 size=2 face=Arial>I built
an 18vdc 1.5 amp power supply using a transformer, bridge rectifier and a 7818
regulator. Works fine, but I need to go to 3 amps. I have been trying laptop
switching power supplies that put out 3 amps that produce noise on my hf rig.
If I unplug the laptop power supply, the noise goes away. The power supply is
used for charging batteries through a solar charger.<BR><BR>Questions: what is
the difference between a regular power supply and a switching power supply?
Can I filter out the noise on a switching power
supply?<BR><BR></FONT></BLOCKQUOTE></DIV></DIV></FONT></BODY></HTML>