New weak signal modes for LF/MF

On the LF-reflector this evening comes news that Joe Taylor K1JT is thinking about the development of some new software for weak signal work on the lower bands. Although Joe has not yet had much chance to start coding development of the new modes, they should lead to even lower useable signal levels. JT8-2 is a couple of dB more sensitive than WSPR but JT8-30 (will take 30 mins to send a message) is likely to be around 12-14dB better. Modulation is a form of 8-FSK.

Mode   T/R   TxT    df    tsym   BW    S/N*
       (m)   (s)   (Hz)    (s)  (Hz)   (dB)
-----------------------------------------------
JT8-1    1    52  1.577   0.63  12.6  -26.9
JT8-2    2   112  0.732   1.37   5.9  -30.2
JT8-5    5   292  0.281   3.56   2.2  -34.4
JT8-10  10   592  0.139   7.22   1.1  -37.5
JT8-30  30  1792  0.046  21.85   0.4  -42.3
-----------------------------------------------
* Noise power measured in a 2500 Hz bandwidth.

How quickly K1JT can do the necessary coding will depend on his work load - he is a Nobel Prize winning physicist - but we are looking forward to the first release of this software in the coming months.

Just to put a measure on this, 12 dB weaker signals (using JT8-30) would mean considerably greater range could be achieved for a given ERP, or the power level of the TX could be 16 times lower for a given range (with WSPR), all things being equal.

Weak signal modes compared

There has been quite a bit of debate recently about just how good certain weak signal modes are when compared against similar modes. So, ON7YD has done some research and straw polling to compare them and published the results on his wonderfully informative website. He asked people to try to decode some weak QRSS signals by eye - these were at defined S/N ratios and compared the results against OPERA at various speeds and WSPR.

Amongst his conclusions is that "Opera8, QRSS10 (or DFCW10) and WSPR should have a more or less equal performance."  This is very much as I have found from practical experience on 136kHz where QRSS3 does not perform as well as QRSS30 which is somewhat better than WSPR. So, WSPR being much the same as QRSS10 seems spot on. The advantage of WSPR is of course the internet database reporting which allows you to see where you have been received. QRSS reports depend on someone decoding the signals by eye and then manually sending you a report, which rarely happens. So, WSPR remains my favourite weak signal beaconing mode.

ON7YD's graph showing the effectiveness of various weak signal modes