[ARC5] Adventures in Battery Ops

[Bill Cromwell]

Hi Les,

I didn't intend to discourage anybody from trying filters on the AC 
lines (or any other lines) into and out of their gear. It certainly can 
be done. I have really power supply here that was sold without any line 
filters at all! I built the filter that should have been there by 
installing the parts in the silk screened locations on the board - after 
removing the jumpers. Since then I have been able to use that computer 
in my radio shack. It sits inches from the station receiver.

One quick way to see if your overwhelming noise is being conducted into 
your radio through the power line is to unplug the power while listening 
to the radio. I know that sounds stooopid but the radio can play some 
some seconds
after you pull the plug. If the noise level drops (mine can vanish) 
revealing weak signals that you couldn't even hear before - well you 
what to do. I am a 200 or 200 feet from the nearest of several nearby 
"industrial" noise source. Those shops are really like "garage" 
businesses on steroids.

The same filters that are supposed to be in those power supplies can be 
added to the power input side of your olde tyme 'linear' power supply. I 
regard those filters as a 'brute force' approach. There are a lot of 
noise sources and some of them are *brute force*, too. Sources like the 
switcher in your mp3 player. Why do you still have that, Les? Some 
people here use naughty items like that for target practice with their 
hunting rifles. If you don't keep and bear arms you might have a sledge 
hammer <evil grin>. I have both and my preferred deconstruction is the 
hammer.

You might also see what you can do to tame that mp3 player. Contact the 
manufacturer and see if they will help. Some of them will. Some of them 
will merely giggle. I have filed complaints with manufacturers and sales 
companies. None of them ever helped me. But I'm more independent (a Yank 
ya know) and I routinely remove the screws under the sticker that says 
"No user serviceable parts inside". That's exactly right. The parts 
aren't there.

The link that Scott sent is a good starting point. I picked up one of 
the units that resembles a long version of the power supply input 
connector and install it in a really nasty florescent light fixture that 
I wanted to use above my work bench. It didn't completely tame the noise 
from the light but it did dramatically reduce the noise. More is 
sometimes better. Maybe one of the models shown there can tame your mp3 
player (I still like the hammer).

My browsers now refuse to display the actual url so I can't paste in a 
working link but search for "power line filter image" and you will get a 
number of schematic diagrams. If you interested in rolling your own that 
will be a good starting place. That is what I did and then discovered 
silk-screened layout for the missing parts the above mentioned power 
supply.I am going to build that into the power supply for my command 
receivers but I need a bigger metal box. The extra parts require extra 
space inside. I don't guess I will need to find an old refrigerator 
<evil grin>.

Meanwhile the batteries are working well for me. Maybe you can use them 
for your naughty mp3 player. And by all means try your 
battery/float-charge system. Depending on how much noise it might be 
enough. One and done :) You will also have backup power at the ready for 
when the power company drops the load.

73,

Bill  KU8H