[Milsurplus] 3A5 Filament Voltage Question

[Al Klase]

Hi John,

I fail to see that 1.4 is defined as the maximum filament voltage, 
rather 1.4 is the voltage at which the typical characteristics are measured.
See: RCA HB3 page here: 
http://www.mif.pg.gda.pl/homepages/frank/sheets/049/3/3A5.pdf

I've always assumed that 1.4 is the nominal filament voltage, and that 
1.5 or maybe even 1.6 is not a reliability problem.  I also assume that 
you should get reasonable performance down to about 1 volts, the so 
called "end point" where the battery has delivered 80+ percent of it's 
available energy.

Here's another situation where I'd really like to see the original RCA 
applications notes that must have existed in one form or another. when 
these tubes were introduced to the market.

Regards,
Al


On 8/3/2013 8:18 PM, J. Forster wrote:
> I'm playing with an ART-4 Transmitter. This unit is for reporting the
> blast intensity near an airplaned towed target tube (sock), hence the
> closeness of the shell to target can be estimated.
>
> Anyway, after tracing the circuit, it has an oscillator and an amplifier
> stage.
>
> The filament on the 3A5 is parallel wired.
>
> The spec sheet says 1.4 VDC, Max. A current alkaline battery will put out
> significantly more than that.
>
> I want to run the thing off an adjustable DC supply, and allow some margin.
>
> Does anyone know roughly what the minimum DC filament voltage to apply for
> enough emission to work reasonably well? I just want to test the operating
> frequency and get a rough idea of the modulation deviation.
>
> Thanks,
>
> -John
>
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>
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/