Hi John,
I spent quite a while adjusting the resistors on my initial filter and it always seemed a little wobbly on the top, I did get a reasonable result eventually but I think my crystals were probably not the best. For testing purposes I bought a whole load of cheap ones so it would not matter if I made any mistakes as they were only a few pence each. You were right in that the resistance should have been around 200 ohms, I got about 260 ohms at one point and the other end was a bit higher.
I always like to try these things initially using cheap components so I do not need to worry about messing them up, once I know I am working along the right lines and I am getting roughly the results I expect I get better parts.
After doing this for a while I got distracted by Larry's videos (see previous post) and spent a while learning the very basics of SimSmith and working out a good LC matching network - this appears to have given me a reasonable looking filter which should be good for my 40m receiver I am designing.
My design is based on the one Charlie Morris is currently working on, I have just modified it to 40m:
Thanks again for the help and suggestions,
Kerr
