[Elecraft] What crystal filter do you use the most?

[Edward R Cole]

Bob,

Good comments.  I think those of us who have been in ham radio for 
many years still think of physical filters as doing the job of 
specifying the radio bandwidth and forget that today's radio often is 
digital or partially digital where DSP does the job and filters are 
only used supplementary to help reject off frequency interference.

I have the 13-KHz filter for FM and can be used for AM which I only 
would use for sw bc where the KBPF3 operates.  the 2.8-KHz filter 
serves 95% of my use even for CW.  The exception is working CW-eme 
where I typically operate the DSP at 100-Hz.  There the 400-Hz 
roofing filter helps improve overall noise rejection and maybe helps 
sensitivity by deepening  the off freq skirts (a guess).  I have no 
local QRM on eme.

I typically tune eme in wide bw until a signal is detected by digital 
waterfall display which I then tune in and reduce bw to hear the 
signal.  My sub-Rx only has the 2.8-KHz filter because I only use it 
for diversity using digital modes or SSB.

But it took me awhile to get my mind to accept that Rx bw is done by 
the DSP and not the filters.

PS:  my new SYN3A and KBPF3 mod kit arrived in the mail today.  Going 
to be interested to see if I see any improvement in Rx sensitivity on 
eme.  Moving below 490-KHz is the other plus as most activity is now 
472-479 KHz.

73, Ed - KL7UW
http://www.kl7uw.com
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