[Elecraft] 250 Hz and 400 Hz Filter Measurements

[Wayne Burdick]

I agree that a narrower 8-pole filter would be very useful.

Meanwhile, those who are interested in a very narrow CW/DATA crystal  
filter might want to consider our 5-pole model. This is one of the  
filters Sherwood (an independent reviewer) used during his K3 receiver  
testing. See the second to last column in his performance comparison  
table:

     http://www.sherweng.com/table.html

While it's true that the 5-pole 200-Hz filter is a bit narrower than  
optimum for 170-Hz shift RTTY, many operators (including me) use it  
for this all the time. The response shape is gaussian at the top, and  
in practice the slight additional loss at the edges has little impact.

73,
Wayne
N6KR