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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>After trying out several ATX power supplies that generated way
more noise into the SDR/J/O system than I could tolerate, I decided to go the
linear route. I bought an old Radio Shack 13.8-volt 2.5 amp power supply
on Ebay for 10 bucks. I also bought an LM7805 regulator (Mouser
512-LM7805ECT) to give me +5 volts, and an L7912 (Mouser 511-L7912CV) for the
+12 volts. For the -12 volts, I bought an 18 volt 130 ma
transformer (Mouser #838-3FD-336), an L78S12 regulator (Mouser 511-L78S12CV),
and a bridge rectifier (Mouser 821-DB102G), and found a handful of junkbox
capacitors. Total cost outlay for everything including shipping is less
than $35 bucks, and it all fits into the original Radio Shack chassis with its integral
power cord, fuse, and circuit breaker. I have ample power to power the
Janus/Ozy as well as the 1W SDR, and probably enough power left over for the
future projects. I’m considering buying two 15-volt regulators to
add to the soup in order to get rid of the +/- 15 volt switcher on the SDR.
And it’s QUIET! No need to go to all the trouble to filter out switcher
spikes (or adjust switcher frequency to get it off the passband). Most
shacks already have a big linear 13.8 supply; the rest is pretty trivial.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>So I vote linear. IMHO, it’s cheap, dirt simple,
and quiet. A little heavier, maybe, and perhaps a tiny bit bulkier, but
it’s much cheaper and cleaner. Remember that we are in an
environment where quiet is paramount.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Someone earlier asked about design of all this. Just
look up the spec sheet on any of the regulators for the circuit.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>My two cents. Thanks.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Ken WR5H <o:p></o:p></span></font></p>
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