> Also note that our 6-kHz 8-pole filter is targeted specifically > at AM operation, and will provide better adjacent-channel QRM > rejection than the FM filter, if needed.
"Targeted specifically at AM operation" is correct only in the context of amateur "communications." The 6 KHz filter bandwidth limits the audio bandwidth to 3 KHz before the skirt selectivity starts to create significant rolloff. If one is looking for SW or MW broadcast reception the 13 KHz FM filter would provide significantly better fidelity - particularly if the 4 KHz DSP audio frequency limit was increased to 5.5 or 6.0 KHz (at least for AM). > A 6-kHz filter is also required for AM transmit (enforced in > firmware). This ensures excellent 2nd-I.F. image rejection. This could certainly be relaxed to allow use of the 13 KHz filter for AM transmit. Even if the 13 KHz filter had only a 2:1 shape factor, with the carrier centered in the filter response at the image frequency (30 KHz away) should be very close to the filter's ultimate rejection ... shifting the filter 2 or 2.5 KHz away from the image in transmit would provide even more insurance against unwanted image response. 73, ... Joe, W4TV > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of wayne burdick > Sent: Wednesday, December 31, 2008 4:17 AM > To: KM5Q > Cc: [email protected] > Subject: [Elecraft] Re: K3 as a SW receiver > > > KM5Q wrote: > > > For AM SW listening be sure to get the "FM" filter (13 > kHz). It gives > > you the width you need for the audio bandwidth you expect. > The normal > > SSB filter (I have the 2.8) is too restricting for AM. > > > > However, I find that switching mode from AM to SSB reduces severe > > fading and distortion, much like AM synchronous detection > does (fills > > in the missing carrier). It's a good technique, at least > until synch > > detection is implemented in the firmware. > > Windy, > > Also note that our 6-kHz 8-pole filter is targeted specifically at AM > operation, and will provide better adjacent-channel QRM > rejection than > the FM filter, if needed. A 6-kHz filter is also required for AM > transmit (enforced in firmware). This ensures excellent > 2nd-I.F. image > rejection. > > 73, > Wayne > N6KR > > --- > > http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
