On Sep 12, 9:34*am, John Smith wrote:
On 9/12/2010 9:32 AM, RHF wrote:

...
Ah OK - I have always figured the required
Voltage Drop needed for the Radio at normal
Audio Listening Level and used a Resistor
-example- 12 VDC down-to 9 VDC -or 6 VDC.

Here you are using a Silicon Diode because it has
the specific ~0.6/0.8 Volt Drop for this application.
http://en.wikipedia.org/wiki/Diode

~ RHF
* .

Yes, if you want to drop the voltage further, just drop more silicon
diodes in series ...

Regards,
JS

HUMmmm the Cost of one Resistor
or the Cost of many Diodes . . .

Somewhere 'somewhen' long ago : I was told
taught to Divide my Dropping Resistor Value by
Two and use Two Resistors in the DC Supply line;
one in each Wire; so that the Battery would be
'isolated' and 'floating' ?

+12VDC [b]__/////__+Radio-__/////__[b] -12VDC