[R-390] Regulated filament voltage

[rbethman]

When one considers the time frame that these radios were built and 
used,  the methods of providing the the power source, and the overall 
use, the entire voltage regulation thread is pretty moot.

The AN/GRC-26D used R-390As in the communications "box" on the rear end 
of a 2 1/2 ton truck.  The power was provided by a generator - of 
limited ability to track voltages when the BC-610, T-213, and /or T-368 
was keyed up.

Any "hairball" idea to build a SS voltage regulator is ridiculous, since 
it creates internal noise to a receiver that was designed to be 
SENSITIVE.  The use of 3TF7s, 12BA6s, or the 40 to 50 Ohm @10W resistor 
is more than adequate.

This entire idea of "attempting" to regulate the filaments of the PTO 
and BFO is like suddenly deciding that you wand Solid State and Digital 
Readout precision.  (That's all flawed in itself!  Whom is it that has 
the *correct* zero beat with WWV?  The signal path pretty well throws 
that all over the charts.)

I take it that "some" would like to include a circuit with GPS ability?  
Yep!  That will really keep the "noise" out - NOT!

Why is it that some folks simply cannot leave this wonderful working 
design alone?  I certainly have YET to see or hear a single individual 
whom has the mental and design wherewithal that equals, much less 
*exceeds* the collective knowledge and wisdom of the entire Collins team.

Bob - N0DGN

On 2/20/2011 10:52 AM, Bernie Doran wrote:
> If regulated fil voltage is so important, why not just regulate the AC line
> voltage and perhaps drop it down a bit? That pretty much covers everthing.