In WSJT's FSK441 screen, there is a useful little window that plots the amplitude of the noise floor and the decoded signal burst, if any, against audio frequency. Since FSK441 uses four tones ranging in frequency from 882 Hz to 2205 Hz, the net passband (after all stages) should ideally be flat from about 850 to 2250 Hz, given good signal frequency accuracy. However, the WSJT FSK441 software is designed to find and decode signals as much as +/- 400 Hz from the nominal receive frequency, which extends the requisite passband from around 450 to 2650 Hz.
With my TS-B2000, I cannot achieve this. Using the widest possible filter selections and the best possible RX equalization and DSP settings, the best that can be achieved is a "sort of flat-ish" hump-backed curve, with both ends rolled off from the center by a dB or two, the high end being rolled off more than the low end. It still "works" (on signals of adequate strength), but it is far from ideal. Is the K3's passband flat over this range of audio frequencies using the 2.7/2.8 kHz filter, or if not, can it be made effectively flat by the use of custom equalization settings? I should think the answer would be yes, but I'd like to hear from somebody who has perhaps done it and seen the resultant flat noise profile in the FSK441 display. Bill W5WVO _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
