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 "Kits made by KL7UW"
Dubus Mag business:
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