Reply to post: Re: DAB is shit

Halfords invents radio signals that don't travel at the speed of light

martinusher Silver badge

Re: DAB is shit

>sell in their electrical shop very big, low voltage dry cells...

Early valves ran with 2 volt filaments so they used a single cell accumulator to power them. The first valves were little more than light bulbs with electrodes in them, they were known as 'bright emitters' and used quite a lot of filament power so an accumulator was the logical choice for power. By the mid-1920s manufacturers had learned to coat their filaments with an oxide coating to promote emission, allowing the filaments to run with a lot less power. Once the valves became miniature (after WW2) the standard filament voltage for a battery radio was 1.5v supplied by a large dry cell. Irrespective of the filament voltage this low voltage supply is known as the "B' in the USA. The higher voltage anode (plate - US) supply is typically 45 or 90volts for a battery radio (a lot higher for mains kit -- I have an audio amplifier that runs 415v on the output stage). This supply is known as the 'A'.

(You may see in very old kit a need for a third battery, the 'C' battery; its typically 9v and provides a bias supply for the valves.)

OK -- a lot of non-computing information but its fun to know this stuff. I'm not that interested in modern radio like DAB because its not a very good solution to a problem that really doesn't exist. I swapped out my table radios years ago for Internet models and even these are now redundant thanks to voice assistants.

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