Notes on meteor scatter. FSK441 versus MSK144


(2017-01-13) PE1ITR

MSK144 is a new digital meteor scatter mode. I am using FSK441 for many years now on 4m, 2m and 70cm and wanted to see if MSK144 is bringing something new to me. I decided to do a laboratory test and compare these two modes with artificially generated audio files.

Added at the end of this page an 20ms short hashed message test in MSK441. Soon I will add some doppler shift tests.

Test Setup
I generated 10 wav files. 5 files with FSK441 and 5 files with MSK144 messages. The FSK441 message is "K1JT PE1ITR R26 R26". The MSK144 message is "K1JT PE1ITR R+10". The FSK441 and MSK144 messages are random chopped in the same way to a pulse like a meteor scatter ping. This way I get comparable situations. After that white noise is added so the signals are "in the noise". The pulse length chosen is 40ms, 60ms and 140ms. In one case I have made a train of four 40ms pings. I generated and decoded the files with MSHV software. The files are also decoded in WSJT10 an WSJT-X software with similar results. It looks like the FSK441 decoder in WSJT10 has some better performance.

Test cases
  • FSK441 one 40ms ping 30sec sample rate 11025Hz
  • FSK441 one 60ms ping 30sec sample rate 11025Hz
  • FSK441 one 140ms weak ping 30sec sample rate 11025Hz
  • FSK441 four 40ms pings.wav 30sec sample rate 11025Hz
  • FSK441 three 20ms and one 30ms pings.wav 30sec sample rate 11025Hz
  • MSK144 one 40ms ping 30sec sample rate 12000Hz
  • MSK144 one 60ms ping 30sec sample rate 12000Hz
  • MSK144 one 140ms weak ping 30sec sample rate 12000Hz
  • MSK144 four 40ms pings 30sec sample rate 12000Hz
  • MSK144 three 20ms and one 30ms pings.wav 30sec sample rate 12000Hz

    Result
    FSK441 is decoding always something with a lot of garbage characters. With some imagination the orginal messages can be discovered.
    MSK144 is decoding al the cases correctly except the case of the 40ms ping.
    In my opinion the result is not bad in favour of MSK144.

    FSK441:


    FSK441 one 40ms ping



    FSK441 one 60ms ping



    FSK441 one 140ms weak ping



    FSK441 four 40ms pings



    FSK441 three 20ms and one 30ms pings


    MSK144:


    MSK144 one 40ms ping



    MSK144 one 60ms ping



    MSK144 one 140ms weak ping



    MSK144 four 40ms pings



    MSK144 3 20ms and one 30ms pings






    20ms short message test

    2 files with in each wav file 2 pings of 20ms. The message is "K1JT PE1ITR R+06". One file the short hashed message option is enabled.



    MSK144 20ms



    MSK144 Short Message Option 20ms


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