[Elecraft] 120V vs 240V

[Lew Phelps K6LMP]

I own a 1929 Hudson Town Sedan. Its  OEM electrical system was 6 volt positive ground. Later Hudsons were 12 volt negative ground.  From my contact with the old car restoration community, my sense is that in the early years (up to about 1950) the industry was about evenly split between positive and negative ground. They finally standardized on 12 volt negative, more or less in the 60s.

Someone raised the question why the auto industry didn't just go to 24 volts.  The answer is battery size.  Trucks, boats, and planes are mostly 24 volts, but they mostly have more room "under the hood" than most autos.  There were only a couple of standard cell sizes available in lead acid batteries, and scaling up to 24VDC even with the smallest of them required dedicating a lot of space to batteries. Those older vehicle engines were not very compact or efficient, by today's standards. There's room under the hood of my Hudson for a 12 volt battery, but not for twice that volume. Most vehicles that have 24VDC systems get there by strapping a pair of 12 volt batteries in series, rather than by employing a single (and more compact) 24 volt battery. That's the situation with a military surplus vehicle I also own, a 1975 Pinzgauer, which serves as a great platform for my VHF/UHF rover contesting station (which is based on my K3, and thus qualifies this post not OT...;-)  )

Lew K6LMP


On Feb 16, 2011, at 4:33 PM, Don Wilhelm wrote:

>  Phil,
> 
> I am stretching my memory a bit, but I "think" I remember my 1951 Ford 
> (my first car) had a 6 volt positive ground system as well - even if my 
> memory is "fuzzy", I do know there was one domestic car manufacturer 
> that used a 6 volt positive ground.
> 
> My 1973 MG Midget was 12 volts negative ground.
> 
> 73,
> Don W3FPR