[Elecraft] cascaded filters for the K2

[Merlarts@aol.com]

Hi,

Anybody out there remember Doug deMauw's brilliant receiver designs, with a 
crystal filter in front of the IF amplifier and another one at the output of 
the IF amplifier?

There is no doubt, for SSB at least, cascaded filters are still the best way 
to get nice steep skirts that are unaffected by close in signals.  The K2 is 
so amazingly good that it cries out for this.  It's awfully good now, with the 
sideband option in there, but with another seven poles it would be as good as 
there is.  Selectivity like the very best commercial radios, but in the tiny 
package of the K2!  I gotta do it.  

My question to all you electron heads out there is:  where should one put the 
second filter?  Let's come up with something that can even be done, maybe, 
without messing up the pristine circuitry up the K2's IF stage.  One way or the 
other, I'm gonna do this this weekend, but I'd be curious as to whether there 
there any thoughts about exactly how some of you guys would do this.  My 
thought is to build another seven pole filter outboard, that would sit, along with 
it's little FET amplifier, on the KSB2 board, tapping into the spot between 
the existing filter's output toroid and the plug that goes into the RF board.  
I'd build it into a little shielded box made out of double-sided PC board 
material.  

Another thought:  if a bunch of us got together and approached International 
Crystal or somebody like them, could we have somebody make an 
honest-to-goodness 8 pole filter to go in place of the existing seven pole job that sits on 
the KSB2 board?  Most of these filter guys need an order of at least a hundred 
for it to be worth their while, but methinks that it would be possible.  

This is not sacreligious!  It's just that the K2 is so remarkable that it 
would sooooooo coooool to have a filter that equals the impeccable design of the 
rest of the radio.  

Regards,

Merlin, W3ICT


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment.  Attachments are not allowed.  To learn how
to post in Plain-Text go to: http://www.expita.com/nomime.html  ---