On Fri, 06 Feb 2009 00:43:09 -0600, Don Foreman
wrote:

On Thu, 5 Feb 2009 21:37:02 -0800, "Bill Noble"
wrote:


"
*ALL* tube-type car radios used vibrators to produce the B+ (plate)
suppply voltage. This was when car radios were AM only -- AM being
much more susceptable to interference than FM is. The radios were
typically quite good because they didn't have much signal to work with
-- a whip is electrically very short at AM band frequencies. They
were typically superheterodynes with a tuned RF stage, though not
typically dual-conversion.

the above is not correct. There were special low plate voltage tubes used
in the late 50s in car radios that did not require vibrators to produce HV -
my 59 cadillac's radio uses such tubes. However, before about 1955 or so,
back to the dawn of car radios, that statement would be true for all radios
powered from the 12V or 6V vehicle power system. Some very early radios
were battery sets with their own B and C batteries

Once again proving that all generalities are false. G
And as far as I know, there was never a purpose built automotive
radio with a "B" and "c" battery.. Lots of home and "portable" battery
radios though.. And "farm" radios that ran on something like 36 or 42
volts - which DID have vibrator power supplies.