[Elecraft] K3 Roofing Filters - Zerobeat

[waltk8cv4612amos at att.net]

Use the shape factor to predict the 60 db down response or band width. 
example = the 200 Hz filter has 4 to 1 so ................... multiply with 
a calculator the 6 db response by 4 and that would equal 224 X 4 = 896 Hz 
and the 8 pole 250 Hz has a 2 X 1 so it is 270 X 2 = 740  !

so the 8 pole is really 156 Hz narrower than the 200 in getting rid of LOUD 
ADJACENT QRM !

You can do the math for yourself ...............

http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters#Roofing_Filter_Response