Why Contestia 250/8?

The Contestia format 250/8 is a good compromise between speed, bandwidth and signal to noise ratio and it is recommended that it should be the default format, like bpsk31, mfsk16 and rtty45.
  • Contestia 250/8 is not too wide, less than rtty45 and the same as psk125. 
  • Contestia 250/8 does not need channels like psk31 and rtty. 
  • Contestia 250/8 has a speed of ~30wpm, 58% of psk31 and 48% of rtty. 
  • Contestia 250/8 has a poor conditions snr of -12dB, so it is 11dB better than psk31 and 16dB better than rtty. 
  • Contestia 250/8 has a good conditions snr of -15dB, so it is 3dB better than psk31 and 7dB better than rtty.
Contestia 250/8 is well suited for HF DX, multihop and difficult path propagation.
QRG +1.5kHz or more up from bpsk31 starting frequency.

    BPSK31 and Contestia 250/8 comparison
    Since BPSK31 is an excellent mode in good and moderate propagation conditions, 3dB in itself is not enough of an improvement to make Contestia 250/8 the automatic choice where there is only white noise present.
    However, Contestia 250/8 passes the flutter fading, polar path, high-latitude and disturbed path propagation tests.  RTTY only passes with high power. Contestia 250/8 and 30W can achieve the same as RTTY with 1kW.
    
    
    MFSK16 and Contestia 250/8 comparison
    MFSK16 2x faster and with a full character set, but has a snr that is 3dB worse and it is ~60Hz wider. Tuning to an MFSK16 signal, when it is near the snr limit, is also difficult.
    Therefore it seems rational to use Contestia 250/8 except when we wish to send a small picture to a ham-friend.
    
    
    
    Olivia and Contestia 250/8 comparison
    
    Contestia is Olivia Lite. Same format Contestia is 2x faster, but Olivia has a full character set and a very slightly better snr.
    Olivia seems to be over-dimensioned or over-designed and too slow.
    However, for a slow QSO from Antarctica to the North Pole, Olivia 125/8 is superb.
    
    
    
    Note: Some fellows prefer small characters, they can use Fldigi http://www.w1hkj.com/ with feature print in lowercase.

    2 comments:

    1. Quote: "Contestia 250/8 does not need channels like psk31 and rtty."

      I don't understand, please explain further. I am not particularly familiar with RTTY, but I've never noticed anyone attempt to "channelize" any of the PSK modes, at least here in North America. Olivia can/does benefit from channels in that "ghost mode" QSO's can happen given how far below the noise Olivia can decode. Since Contestia is only slightly less robust, why wouldn't channelizing still be a good option, particularly during poor condx? Might even be a good practice all the time, although I wouldn't get upset and refuse a CQ I noticed because someone is "off channel". Even in good condx it should be a great way to maximize DX, particularly when QRP. So we may not NEED to channelize Contestia (as I understand the the channel concept), can't it still be beneficial? With these modes what you cannot see or hear CAN still make for a very nice QSO! Only by using a pre-determined channel can we find a call to answer or will someone find our CQ in those conditions. Or is this where we just default to Olivia anyway?

      Good article, by the way. I like seeing Contestia being discussed almost as much as I enjoy seeing it used!

      de Stu AF6IT af6it@sbcglobalnet

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    2. Dave - G3ZXXNovember 14, 2010

      Hi All,

      Contestia, could well benefit from channalisation as 'Anonymous said...'

      It is also useful to see that Lauries' superb 'HamSpots' has a listing at: http://hamspots.net/contestia/, and that Philip has added the mode to his superb "PSK Reporter" at: http://pskreporter.info/pskmap.html

      However, I feel that it could well be of use to have an on-line meeting point. Where users can leave messages, have real-time text exchanges, and see reception reports, etc., as per JT65 HF users.

      Take a look at the excellent site: http://jt65.w6cqz.org/

      I am sure that such a site for Contestia, would be of considerable benefit.

      Sorry, I don't have the skills to do it, other wise I would offer.

      73's
      Dave, G3ZXX.

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