I've found an excellent bandpass filter. It's 4 pole and is supposed to be a
CW filter. When I tune it up, it works really nicely to pass about 250hz 3dB
bandwidth, then has incredibly sharp edges so at 500hz BW, it's about 20dB
down, and then just rolls off more. This is almost perfect for what I want.

Now the only thing is finding a tight notch filter that does similar, but
the opposite, the tighter the better. Really I want to try to kill off my
1khz carrier, when it's no more than 50hz away, so it needs 100hz BW then be
rolled off at about 200hz.


After I've got these circuits sorted, I might be ready to "trial" earlier
than I originally thought.


Sam

"Samuel Hunt" wrote in message
...
I'm looking for a circuit design to a CW filter centred around 1khz that's
about 200hz wide and then rolls off very rapidly.

I'm planning to build a AFC system for SSB, which has a 1khz pilot tone
that will be used to lock the frequency correct.

I then need a circuit with quite a tight notch around 1khz to kill off the
pilot tone once it's been locked on, so you don't have an annoying whistle
on the reciever.


Can anyone possibly help with any circuit designs or where I can find
some????

I've had a look at a twin tee filter, but I'm not familiar with this
design. Would this be suitable, is it worth me reading more about it and
learning, then using this?


Thanks all,

Sam