22 Sep 2012

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.

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