![]() ![]() In this case it was the detection of the subaudible tone transmitted by another station. Several years ago, I was one of the main people behind the code on the mcHF SDR transceiver and I ran across a "problem" with the Goertzel that I'd encountered when I'd used it before: Trying to make sense out of the detection value it produced. CW skimmer or MRP 40 will probably be even better for weak signals. These numbers are with daytime band noise present at 14 Mhz. I used a virtual audio cable and compared the results with Multipsk in CW QRP mode, this program copies to about -115 dBm. In any case as others already mentioned it is hard to beat morse code processing by our brains, especially when it comes to hand keyed signals with imperfect timing in the presence of noise and other signals. Still not a bad result although it would certainly be nice to decode even weaker signals that are still readable on the waterfall. "Training" can be forced by clicking the threshold correction button but in my tests seldom recovers the situation. Reducing the signal below that decoding starts to fail. ![]() It seems the decoder has a reasonable tone tracking range for stronger signals down to about -108 dBm. My initial suspicion that the CWN filter pass-band and the decoder center frequency did not match was incorrect and caused by a frequency error in the RF signal I used previously. Tried combinations of the above parameters and this time used a GPS disciplined cw rf test signal.
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