[Milsurplus] [Boatanchors] 3A5 Filament Voltage Question

[mac]

The BC-1335 uses four 3A5s with parallel wired filaments in the  
transmitter section.  I've had excellent results using series pairs of  
forward biased 1N4007 Si rectifier diodes as shunt regulators on the  
1.5 volt filament strings in this and other radios using 1.5 volt  
tubes (BC-659 for ex).

Dennis D.  W7QHO
Glendale, CA

*********
On Aug 3, 2013, at 5:18 PM, J. Forster w

> 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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