Wednesday, November 21, 2012

DC power grid still runs in San Francisco

DC Elevator Motor
Fascinating bit of techno-history persisting in the modern day. .
In the early days (ca 1920) some hams could run their radios with the "B+" (plate voltage) coming straight from the DC power mains, saving money on expensive power supplies.  But if you needed high voltage for your transmitter's final, you might have needed a motor-generator (dynamotor). That would have been a big expense compared with an AC transformer/rectifier.

1 comment:

Bill WA6OHP said...

That could be a real pain. If the voltage was high enough to run the tube plates in the receiver or lower stages of the transmitter then the filaments would have to be series like the All American 5 AC/DC radios or one very big resistor to drop the voltage. AC has made things a lot easier for us.