Why 6.3 volts?

I said they were not talking to each other. They weren't. Period. It doesn't have a goddamned thing to do with something snipped, idiot.

They were receive only at first, and that reception was from the dispatcher only, and even when they went to transceivers, they communicated with the dispatcher, not each other.

It is.

He is.

I replaced enough of the damned things with open filaments caused by burnt out pilot lamps. Most manufacturers were too cheap to add the fixed resistor across the lamp to protect the tube, since the radio would be long past the warranty when the lamp failed. It was such a comon failure that some shops put up a small sign over the radio bench to remind the new techs to always check the pilot lamp before doing any other work on either type of AA5. The octal version was the 35Z5.

You're welcome. :)

And you claim this was true throughout the 1930s?

John

Maybe this contributes to their popularity:

"The most significant difference arises because the voltage along the filament is not constant, but varies from one end to the other by the applied filament potential. Although this potential is small, it must be remembered that the effective plate voltage as seen at the cathode (filament) is also small. For example, a 300B operating under quiescent conditions of 350V and 90mA, with ?60V on the grid, has a potential as seen at the cathode of around 15V, against a filament voltage of 5V. At the negative extreme of grid voltage, modulated by the signal, this effective voltage will drop close to or even below 5V."

I bet I could sell this fact to audiofools as being the reason 300Bs are good in audio amplifiers!

I built an amp with 300Bs about fifty years ago. It did sound pretty good! I have a couple of the tubes still and at the price they get on eBay I should sell them.

The most intelligent thing you have said.

Diodes intended for use as noise sources used plain tungsten filaments, so that noise current could be controlled by filament current, which won't work with thoriated tungsten.

The tubes used in the finals of early British CH radar (around 45MHz) were demountable for filament replacement. A guy who once worked on them told me that the filaments looked like bent six-inch nails. Obviously the tubes were continuously pumped.

Same guy showed me some photos of a BBC MF transmitter of the '50s. I was intrigued by a row of what looked like plating motor-generator sets. Those were the filament supplies. Hundreds of amps at a volt or two.

There were some European transmitting tubes for mobile use (QQZ06-40, a quick-heat variant of the 6.3V indirectly-heated QQV06-40) that used directly- heated filaments. The filament supply only came on when the transmit switch was pressed. Those tubes ( push-pull dual tetrodes) also had built in neutralizing capacitors. Good up to 450MHz, and real easy to get going.

European cars mainly used 12V systems as far back as the 1930s.

I dont remember specifically any European cars from then except Volkswagen ( 1950's ), which was 6 volt, but the English Fords, Morris and Austin certainly still had 6 volt systems in the 1950's. They were all renowned for having extremely poor lights.

A google search would probably give you a whole lot more info.

My Austin-Healey Sprite, ca 1969, was 6 volts, positive ground. Of course, it was an antique when I bought it, brand new.

John

All the Spridgets I've seen (including the frog-eye) were 12 Volt, positive ground.

those

Why

was

=20

=20

There is also the advertising baloney part to be able to say "Under = twenty dollars". Hmm, yes, it is; just not significantly so.

?-)

That's the reason the Brits drink their beer warm ... Lucas refrigerators.

Jim

Critical price thresholds are very real at auctions.

Particularly the "don't go there's" of $20, $100,, and $1000.

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