Don, > While we are on the subject, I might say something about very low > pitches (since it has been mentioned) - there is a limit to how > low you can go and still retain the single signal reception because > a significant amount of the filter passband crosses over from zero > Hz pitch to the other sideband. In the extreme, you end up with the > response like a Direct Conversion receiver where the same pitch can > be heard (at equal amplitudes) on both sides of zero. One must > consider the IF filter skirt slope when deciding how low the filter > can be set while still retaining single signal reception.
How does (if it does) this change when the second filter is a DSP filter/demodulator working at IF instead of at audio? For example, in the K3 with the 500 Hz (565 Hz SF=3.1) roofing filter set for a 250 Hz pitch the IF will have significant bandwidth "below zero beat." If the DSP is set for 200 Hz bandwidth, will it include response at the "audio image" or does the K3 DSP "filter before demodulate?" 73, ... Joe, W4TV _______________________________________________ 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
