"author" wrote in message news:01c3d31c$aa2c97a0$53c44a43@gwg1...
The power supply in my radio has audible hum in the background
and bypassing the diode rectifiers with capacitors does not eliminate the
hum. There is no hum when using battery power. The solution is to
build my own power supply. Does anyone have a design for a compact 6V
supply that I could build for this purpose?

First, don;t bother repsonding to the r2000swler@hotmail account, I
have
abandoned it because of all the porno spam I was receiving.

I am assuming you are talking about a modern, low power receiver, and
not some sort of ancient tube boat anchor. While high current, low
ripple
supplies can be built, they are very complex and expensive.
I would suggest a metal case, aluminium is easy to work.
For a 6V output I would start with 120V to 12V transformer. Radio
Shack
transformers will work, but if you could find a 30+ year old one made
by
Stancor or Triad, it will run much cooler (more iron in the core).
Buy or build a full wave brigge rectifier, and bypass each diode
with a 0.01uF cap. Use as large a filter cap, at least 1000uF(@20V),
but
as large as 20,000uF(@20V) will not hurt. Also use a
10uF(@20V)tantalum in parallel with the main capacitor. Then use a
7806 (or a LM317 or LM338 for higher current with the correct
programing resistors to set the output at 6.0V)
Add a 100uF(@10V or 12V) across the output of the 7806. I have found
the LM317, with the voltage set point bypassed by a 10uF(@12V) to be a
little quiter
then a 7806. Either will be much quiter then almost any "store bought"
power supply. If you want to get fancy, put a corecom RFI filter on
the AC
mains input and do not use a neon pilot light, they often add a lot of
hash.
I have had good luck not connecting the ground of the DC out to the
power mains ground, it seams to always add a lot of noise. I prefer to
only ground my radio to a "real" ground.
You may have to mount the 7806 regulator on a heatsink, but for most
modern
SWs the metal case will work fine. Oh and be sure to add a 1amp fast
blow fuse on the input. You could also just get a 12V DC wallwart and
build a 7806 add on
regulator. The main issue with that approach will be the difficulty of
gaining
access to bypass the internal diodes. A better approach would be to
find a 12V AC (lots of modems use these) wall wart and then you will
use a bridge internal to your regulator.
Go to your local library and look for the ARRL handbook, or for any
"electronic
project" book, they all should have similar diagrams.
Good listening.