[Elecraft] KRX3 roofing filter matching for diversity receive

[Chuck Guenther]

Stan, you asked a good question-- one I asked about some time ago.
When I worked in the aerospace industry, I designed and used analog
and digital filters for measurement applications.  Most textbook design
formulas and procedures are based on 3 dB bandwidths, although sometimes
our measurement requirements demanded 0.5 dB bandwidth.

Amateur radio IF bandwidths seem to have been standardized at the 6dB
points.  If the filter designers are reporting 3 dB points, this might 
account for the
difference you asked about.  BTW, I just checked the INRAD website and 
looked
for the filter curves for the K3 roofing filters and couldn't find 
them.  They used to
be available there. 

73,
Chuck  NI0C
K2-10 s/n 5853  K3 s/n 1061


Stan Rife, W5EWA, wrote:
"I'm not sure why a filter would be advertised as a 250hz filter but 
actually have
a (usable?) bandwidth of 370hz. Is this just a difference in how it's 
measured? "