On Sat, Apr 17, 2010 at 6:59 AM, Pino Zollo <[email protected]> wrote:
> Hi, > > I made two QSO's in Contestia.... > > It works fine but the water-fall was not showing anything. > > Is this because Contestia is so sensible to decode extremely weak signals > or > is a problem ? > The water fall was showing other PSK31 signal in the band. > Contestia and Olivia are virtually identical CODECs. Their performance is going to be within one or two dB of each other so what you expect from Olivia you can expect from Contestia. Contestia uses a small character set so it needs fewer bits transferred for the same message. This also means that you don't get lower case letters and many punctuation symbols you can send with Olivia. Also Contestia has a smaller block size and shorter interleave. This means less delay but less resistance to long fading (QSB). If you increase the interleave to provide QSB resistance you can expect longer delays (latency) before copy starts. In this same family of protocols you will find MFSK16, DominoEX, and Thor. Olivia, Contestia, and MFSK16 all share the same base modulation -- m-ary frequency shift keying. The differences are in the alphabet/character-set they use, the symbol (baud) rate, and the robustness of the forward error correction (FEC). If you set the #tones (always a power of 2, e.g. 2, 4, 8, 16, 32), symbol rate (determines tone spacing), and level of FEC the same on these protocols, they will provide the same speed and weak-signal performance. (Soapbox -- We would be better served by having just one of these modes and then allow selection of the tones, baud rate, convolution polynomial, block size, interleave factor, and Viterbi decoder settings and then transmit that in something equivalent to an RSID header.) DominoEX and Thor use a novel and, frankly, better modulation scheme than the pure MFSK used in MFSK16/Olivia/Contestia. All other things being equal, if you were to put DominoEX with FEC or Thor up against on the three other above but ensure that you are using like parameters for baud rate, convolutional coding, and FEC, DominoEX and Thor would be easier to tune and more resilient in the presence of doppler. In other words, they would flat-out work better. I apologize for what is a really long answer to your question. I hope it helps to understand the differences and to set reasonable expectations for performance. Hmm, it would be great if there were a table that listed the basic parameter differences between modes so we could pick the one that best met conditions at the time so as to provide maximum throughput at 100% copy. Frankly, most of the time Olivia is overkill but it also provides the most robust FEC and interleave so it will get through under the worst conditions when the other modes are failing. -- 73 de Brian, WB6RQN/J79BPL
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