- Jan 1, 1970
Dave said:Uh HUH. Okay. I do appreciate the help. I am currently working with a
big, clunky variable capacitor and some RF chokes, connected by wire and a
switch (to choose which inductor is in the circuit). Unless I am
my R is already quite low because of this. So I should ADD R to the
Would it be best to have a 1:1 relationship between R and X(L)? Or should
go for 2:1, 10:1, or 100:1? My old textbook doesn't seem to cover
like this. One more thing, are RF chokes okay for tank circuits, or
should I try something else?
Thanks much for the help...
If you are at frequency F, X(L)= 2 x Pi x F x L, where F is in Hertz, and L
is in Henrys. So, at 8 MHz, for example, a 10 uH inductor has a reactance of
2 * 3.14 * 8E6 * 10E-6 = 50.24 Ohms. If you want the Q to be at least 100, R
has to be 50.24 * 100 = 5024 OR GREATER,
RF chokes are NOT OK for tuned circuits. They are specifically made to be
fairly low Q. I don't remember what your load was, but the gate input of a
FET is about as good (high impedance) as you can get. What is your
frequency, what Q do you want, and what is the load impedance. What are you
driving it from? that has an effect also.