Take a look at lowband filters and duplexers from CellWave, Telewave,
etc.
Your filter is going to be a coaxial cavity about 2mx20cm with piston
for tuning.
I am sure there are some better approaches to your task
Vladimir Vassilevsky, Ph.D.
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
Paul Burridge wrote:
Hi chaps,
I've decided to bite the bullet and try to build an RF filter for
40Mhz. This filter will ideally have a very, very sharp characteristic
at one single spot frequency +-20Khz and attenuate the crap out of
anything either side of this. It'll need to be tunable over a range of
say 200Khz. Can anyone give me a steer on what type of arrangement
would be best suited to fit this purpose?
Thanks,
p.
--
"I believe history will be kind to me, since I intend
to write it." - Winston Churchill