[ARC5] [Boatanchors] 3A5 Filament Voltage Question

[J. Forster]

Ah! I like that because I can simply tack it across a current limited supply.

Thanks,

-John

================



> 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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>