[ARC5] Loctal Tubes

[Richard Knoppow]

----- Original Message ----- 
From: "Bill Fuqua" <wlfuqu00 at uky.edu>
To: "Mike Morrow" <kk5f at arrl.net>; "ARC-5 List" 
<Arc5 at mailman.qth.net>
Sent: Tuesday, May 01, 2012 9:09 AM
Subject: Re: [ARC5] Loctal Tubes


>   Using 7 and 14 as first digits and also sometimes an odd 
> last digit, not
> always the element count.
> They were able to create a new series of tubes. Most of 
> the times the last
> digit was accurate but to
> prevent confusion they did not internally connect the 
> suppressor grid thus
> increasing the count.
>   Also, by stating 7 and 14 as nominal voltages suggested 
> that the tubes
> were more compatible with
> mobile use since the drain on the electrical system would 
> cause the
> generator to kick in and increase
> the voltage across the battery terminals.
>    This is not from any historical information. It seem 
> like a plausible
> explanation for the odd numbers.
> The fact is locatal tubes were easier to manufacture than 
> octals and was
> the predecessor to the
> miniature tubes.
>
     This has been about beaten to death but I got curious 
after stating that I thought filament voltages may have been 
dictated by batteries.  I have before me a QST for September 
of 1926.  There are not much specific data on tubes (a 
couple of transmitting types) but a lot of ads for 
receivers, batteries, and AC adaptors for battery receivers. 
For instance RCA advertises its Type 104 loudspeaker with 
power supply which "eliminates the need for B batteries in 
most receivers", made to operate from 110V 50 or 60 cycle 
current.  There are many other battery eliminators 
advertised.  Batteries are advertised by Eveready and 
Ray-O-Vac.  A distributor advertises the RCA UV-216 
rectifier with filament voltage of 7.5 volts, advertised to 
withstand AC input up to 750V. There is also an article on 
the Radiotron UX-210  (AKA type 10 tube). Specs are:

Filament Volts 6.0 to 7.5 as an amplifier and 7.5V as an 
oscillator, 1.25 max amps for either.
     My RCA RC-14 (1940) tube manual has a few tubes that 
must date from very early in cluding the 00-A and 01-A, both 
5V tubes.  Other 2 digit numbered tubes are of variabl3 age 
but have heater voltages of anywhere from 2.5 to about 10 
volts.
     None of this proves anything other than filament 
voltages for receiving tubes appear to have been 
standardized around the 1930s and AC was beginning to 
replace batteries by the mid to late 1920s.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com