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Small bandwidth digital

Discussion in 'Working Different Modes' started by VK2FAK, Nov 9, 2010.

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  1. VK2FAK

    VK2FAK Ham Member QRZ Page

    Hi all..

    I wonder if anyone has done any testing on the smaller bandwidth option of some modes..

    eg MFSK4 DominoEX4 ....you get the idea..

    I have seen a few propagation testing using some modes..but they seem to have been done some time ago....and for some reason they start out showing details of modes...but then they never show up again in actual testing data...

    I have been looking but just find the same document taken to other sites.

    Anything new..and covering as I say...the more band friendly option of modes.

    John
     
  2. AD7N

    AD7N Ham Member QRZ Page

    Check out www.WSPRnet.org for a real, live narrow bandwidth beacon network.

    In terms of narrow-bandwidth of particular modes like DominoEX etc I am not sure where to look. The only active narrow bandwidth modes I regularly see are PSK31 and JT65.
     
    Last edited: Nov 9, 2010
  3. VK2FAK

    VK2FAK Ham Member QRZ Page

    Hi all....

    Yes I have played with JT65 and is enjoyable to make those long distant contacts with very little power.....but to be able to chat (slowly)...most don't ever consider the smaller bandwidth mode options....and as I say...I can"t find any testing done to see if over the long haul there better or not....the tests just seem to test the popular modes and the popular variations of those modes.

    John
     
  4. M0WAN

    M0WAN Ham Member QRZ Page

    I have conducted many tests with various digital modes, all performed off-air.

    How can that be, I hear you ask.

    Well, wire up the output of one computer to a speaker, and have another with a microphone installed. (Obviously install the necessary software on both.) Seperate the speaker and mic by a good distance, maybe opposite sides of a room or even different rooms, and test away!

    You can reduce the volume of the 'transmitter' to test readability in noise, and the reflections around the room very well replicate multipath. Maybe more people should test this way.

    Although I have not documented my results, BPSK31 fares the worst by far due to multiple reflections causing phase distortion, being unreadable even with a good strong trace, and Olivia 1000/32 and 500/16 doing well in all respects, including dealing with the multipath and low level signals. Slower Olivia modes were even better, but are very slow to use.

    I did try other modes with forward error correction, but Olivia was still significantly better than DominoX 4, MFSK flavours and JT65.
     
  5. VK2FAK

    VK2FAK Ham Member QRZ Page

    Hi all...


    It does seem that some of the small BW options in the modes have the best sensitivity....but not always good under all condition...

    I know DomEX 4 is bad under certain conditions....the Olivias seem to hold up ok...

    I would like to see how the THOR range goes ..have only ever seen tested the THOR 11 and higher...not THOR 8 ,,,as THOR uses a better FEC value, around 10 while normal DomEX can use only a 4 as standard.

    Also...MFSK16 is almost as good under testing as Olivia....but have not seen a test on MFSK8 which is a little slower but is suppose to be 2 db S/N better than MFSK16......I guess tuning still remains an issue with this mode but when you can zoom in on the waterfall I would think it should help this quite a bit.
    JT65 not as good as Olivia....I would question that statement...lol

    But you are right..one of the worst modes PSK31 is the most popular...the argument to using it in days gone by, was that it could easily be spotted...but now with RSID...all that should have changed..


    John
     
  6. AD7N

    AD7N Ham Member QRZ Page

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