[Elecraft] K3S QST Article

[K9MA]

The reason DC power systems in vehicles and aircraft used 28 V or less 
historically is that that was the highest DC voltage that could be 
switched mechanically without excessive arcing.  (Has to do with the 
energy required to pull electrons out of metals, I believe.)  With the 
solid state switching devices now available, of course, higher voltages 
could now be used.

OT, I know, but I always thought that was interesting.

73,

Scott  K9MA

On 10/15/2016 19:46, ab2tc wrote:
> Hi,
>
> Well, as I remember it there was once a push to move to 48V for automotives
> but that never happened (so far).
>
> I was always skeptical on the wisdom on moving to FET finals at the 12V
> level. Generally bipolars work better at this low voltage. FETs come come
> into their own at higher voltages (24-75V).
>
> In general I still think it is silly to make modern radios compatible with
> the old 12V car power system. For portable use there are plenty of ways to
> provide higher voltages. (Eventually power supplies manufacturers will make
> notice.)
>
> AB2TC - Knut
>
>
> David Gilbert wrote
>> There was a major initiative at least 15 years ago in the automotive
>> industry to go to 28 volt systems in order to reduce the cost and weight
>> of the heavier wires that were needed to cope with the expanding current
>> drain as more things in the car went electronic. Not sure what happened
>> to that since I've been retired, but I assume ways were found to make
>> the new electronics more energy efficient in the first place.  As I
>> remember, one of the issues holding back 28 volt systems was the higher
>> breakdown voltages that would be needed for the various semiconductors
>> involved ... not everything gets more efficient or cost effective as
>> voltages go up.
>>
>> 73,
>> Dave  AB7E
>>
>>
>> On 10/15/2016 12:49 PM, Ron D'Eau Claire wrote:
>>> And therein lies the reason for using 12V. It would have been easier had
>>> we
>>> gone from 6V automotive power to 28V as is used on many aircraft so
>>> manufacturers were encouraged to build generators and equipment for that
>>> voltage, but that didn't happen.
>>>
>>> 73, Ron AC7AC
>> ______________________________________________________________
>>


-- 
Scott  K9MA

k9ma at sdellington.us