Re: LED Power Output Indicator #ubitx

Jerry Gaffke
 

Simple as it is, could be I don't fully understand the circuit.
But I don't think you get a voltage doubler unless you add the extra cap in series with the 5.6k resistor
as suggested in the last paragraph of my previous post  (ignore the garbage after my signature).

In my calculations, I'm assuming an LED forward voltage of 3.0 volts.
That's typical of the very bright white light LED's, 2 volts is more typical of a little red LED.
But the extra volt is probably needed to see anything at all anyway, given the 5.6k resistor
and that diode conduction occurs only on RF tips.   Even in a very dark room.
But should be reasonably bright with 5 or 10 watts.

Jerry


On Tue, Jul 3, 2018 at 08:25 pm, R. E. Klaus wrote:
Doesn't the 2 diodes and the cap form a rudimentary voltage doubler similar to those used in old AC/DC radios?

 

 

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