R: [amsat-bb] 2.4GHz Interdigital Filter design wanted

["i8cvs" <domenico.i8cvs@xxxxxx>]

----- Original Message -----
From: Phil <phil.g4iio@ntlworld.com>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, April 05, 2002 9:52 PM
Subject: [amsat-bb] 2.4GHz Interdigital Filter design wanted


> Hi and thanks for reading this..
>
> I am looking for an interdigital filter design suitable for use with
> AO-40.
> A friend of mine has offered to mill out the cavity from a solid block
> of aluminium.
>
> Can anyone recommend a design for such a project?
>
> Thanks in anticipation,
>
> Phil
> G4IIO
>
> www.g4iio.com
> phil@amsat.org

Hi Phil, G4IIO

I built and i use succesfully a very efficient interdigital filter for 2400
MHz described by Richard L. Campbell, KK7B  originally described
in "Proceedings of the 1296 and 2304 MHz Conference, Estes Park,
CO September, 1985 ,"A Clean Microwave Local Oscillator "article

Dimension and drawing are tabulated from 758 to 3456 MHz including
2304 and 2420 MHz and so i interpolated sizes to 2400 MHz without
any problem

The size for 2400 MHz is very small 32 x 31 x 11 mm outside dimensions
and this filter works great attenuating and rejecting more than 60 dB the
 image frequency at 2112 MHz wich is the case using 144 MHz IF and
thearby greatly improving the S/N ratio at 2400 MHz

I have this filter between the output of my 2400 MHz low noise preamplifier
antenna mounted and the input of my 2400 MHz transverter with 144 MHz IF


As a separate post i have included  a picture of  my duplicated filter when
open and two possband curve of the filter response as taken on my spectrum
analyser

Also i recommend to read the article " Computer-aided Interdigital Bandpass
Filter Designe" by Jerry Hinshaw , N6JH and Shahrok Monemzadeh described
in Ham Radio Magazine January 1985


73" de i8CVS Domenico



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