That's true when speaking of the heterodyne between the BFO and the carrier of the AM signal when receiving an AM signal in SSB mode. In either case, if you have a second signal close enough to the frequency of the desired one so it produces a heterodyne in the audio range, it'll produce a heterodyne in either AM or SSB mode.
For an AM Ham rig with a well-shaped audio response that is limited to about 3 KHz, there's little difference between the 2.7 or 2.8 kHz filter in SSB mode and the 6 kHz filter in AM mode. However, for receiving broadcast signals that use a full 5 kHz or more of audio bandpass, superior reception is provided by using the 6 kHz filter in SSB mode, since that allows audio frequencies up to 6 kHz to pass through. That's the way I do most SWL-ing with the K3, since using SSB mode also avoids the problems with selective QSB that shifts the phase and amplitude of the carrier relative to the sidebands, producing a lot of distortion. I find the audio quality in SSB mode with the 6 kHz filter is superb on AM broadcast stations. Since broadcast stations stay within a Hz or so of an even frequency in kHz, and it's simple to calibrate the K3 readout to be within a Hz or so of the indicated frequency, it's easy to tune them in perfectly, even if you don't have the ability to hear audio tones well. Ron AC7AC -----Original Message----- John, AM reception in SSB mode will allow you to receive with good quality (up to 2.8 kHz of audio passband). With the 6 kHz filter, you will be able to receive an audio passband up to 3kHz wide in AM mode. The audio should sound the same either way So the answer is - if you want to avoid the hetrodynes while tuning in SSB mode, yes, you will want to tune in AM mode and that will require the 6 kHz filter - if you don't mind the hetrodynes (only while tuning), then the 2.7 or 2..8 kHz filter will be fine. Once the AM station is properly tuned, there should be no hetrodynes heard. The 6 kHz filter is required for AM transmission. 73, Don W3FPR John Silva N3AM wrote: > In addition to the KBPF3 General Coverage RX module, is the 6kHz > filter required for improved quality AM reception? > > > Thanks, > John N3AM > _______________________________________________ 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
