[NJARC] Switching supplies

[Al Klase]

Hello Edward,

I'll share some thoughts here.  First, you're off by more than a factor 
of ten. 400 mA at 100 V = 40 watts.  A typical battery portable is going 
to draw something like 15-20 mA.  So, for casual operation, a string of 
nine-volters, even cheapies from the dollar store, is not a bad 
solution.  You do need a bunch of battery clips, as soldering often 
destroys the internal connection. 

On the surface, a voltage converter and low voltage batteries seems 
appealing.  However, building such is more of a problem than you might 
think.  Appropriate magnetics (transformers) are hard to come by.  To 
maintain efficiency, a proper design should use a switching REGULATOR 
probably an IC, e.g. the "Simple Switchers" from National Semiconductor. 
  Everything has to be thoroughly shielded and filtered to keep RF hash 
out of the radio.  You'll generally need an extra switch to turn the B 
battery on and off..

I don't want to discourage you, but there are a lot of reasons more 
people don't do this.

I needed 135 volts a substantial current 30-40 mA for an Army BC-322 
transceiver.  I discovered the dollar store had carbon-zinc AA cells at 
8 for a buck.  Better yet, they were the old-fashioned design with an 
exposed zinc can that makes them easy to solder.  I built a simple jig 
to easily assemble 15 cells into a 45-volt module wrapped in duct tape.  
These are perhaps too large for many portables though.

Looking for other suggestions,
Al

edotte at optonline.net wrote:
> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Hello all,I hope everyone has enjoyed their holiday off. And to all who have served, thank you. And to the men and women who died to give me this day off and enjoy it in the greatest nation on earth, I wish I could thank them.Anyway, I have a question. Does anyone have a neat little schematic for a switching power supply replacement for a battery? I see many "portables" had 90 V or 100V batteries and I figure they may have drawn up to 400 milliamps. I figure most are around a few hundred.milliamps.  Anyway I know  you get the point.  But if anyone has or knows of a switching design that is compact, efficient,   and cost effective and would like to share it I sure would appreciate it.Edward
>
>   

-- 
Al Klase - N3FRQ
Flemington, NJ
http://www.skywaves.ar88.net/