MAc wrote:
Hi All
I'm trying to use TQF9-02 (similar to xf9b)(impedance 500ohm) filter in
receiver on MC3362.
In original project there was homebrew filter connected to pins 17,19
MC3362 via capacitors 220pf.

Have you any ideas for proper termination of Xfilter?

MAc

Andy writes:

If the specified filter termination impedance is 500 ohms, you have
to take the 3362 input impedance and transform it to 500 ohms.
I don't know the 3362 input Z, and am too lazy to look it up, but most
likely it is higher than 500 ohms and has a capacitive component...
So, use math to find out what the parallel R and C is, and things
will start to make sense...

Lots of ways to do this, but ALWAYS use a tuned circuit. Otherwise
you will have a reactive component that will mess you up...

Personally, I like to use an inductor and two capacitors, since it
provides DC blocking. Some people like transformers......

Andy in Eureka, Texas

PS Rp = Rs (1 + Qsquared )\

Xp = Xs ( 1 + Qsquared) / (Qsquared)

Q = Rp / Xp or Q = Xs / Rs

If you put these in a Basic program, and learn to use them, it
makes things a lot quicker....