Hi all
thinking of place a 9mhz roofing filter after the first mixer (SBL-1)in the rcvr.
but it will have to have a BW of about 16khz!, to allow for FM BW
i was thinking of designing a 9 MHZ roofing filter with a BW of 16khz, with 9mhz crystals.
can anyone help with such a design ?
Thanks
Hamopp

 

Hello,

You should be able to design a filter with the free ADEE Filter design software:
http://www.aade.com/filter.htm

Bertus

 

Hi
wow that is some learning!
any hints
is it best to get the crystals first, do they have to all be 9.0000Mhz ?
which is the best type of filter to use ?
the sbl-1 mixer output is 50Ω, so is that the filter input ?

as you can see i have not done anything like this before, i just buy filters
but i could not find a 9Mhz @16Khz BW filter.

Thanks
hamopp

 

Hello,

Have a look at the following PDF:
http://pages.suddenlink.net/wa5bdu/crystal_slide_show.pdf

Bertus