light sensitive VFOs &c


Date: Sun Oct 16 1994 - 20:10:14 EDT

I just read the note about a vfo that shifts when you
put shade over the board. It's the diode between the
gate and ground what's doing it.
I think I read about this in a Bill Orr column many
years ago. My marvelous pornographic memory keeps me
from being more precise. Anyway, it turns out that
the 1N914 between the gate of the FET and ground
will pull the frequency with light.
That's why I never test for drift or pull or shift
until the circuit board's wrapped up in a box tight
as a submarine running qualification trials.
But then, think of using an LED over the diode for
FSK. Ah, the wonders of modern technology.
That's why, even though the sign in the Wendy's down
the road has a list for Kids Salad Bar, they won't
sell my six year old one because there's no button on
the computerized cash register for Kids Salad Bar.
Is working for Dave great or what?


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