[digitalradio] S/N Multipsk figures -- JT65A vs Olivia and others
Hello to all, Comparizon with S/N Multipsk figures. According to JT65 specifications, this mode decodes with few errors down to -23 dB, with a normalized band of 2.5 KHz. All Multipsk figures are normalized with a band of 3 KHz. -23 dB in 2.5 KHz is about -24 dB in 3 KHz band (-23.792 dB exactly). This figure of -24 dB can be compared to Olivia 250-8 which has a minimum S/N of -14 dB. So JT65 is 10 dB better or 10 times better. But of course JT65 is much slower that Olivia 250-8. The only modes which are close to JT65 are: * THROBX: Lowest S/N: -18,5 dB for the 1 baud, -17.5 dB for the 2 bauds * PSKAM10: Lowest S/N : -19.5 dB In conclusion JT65 is better (under S/N criteria) that any modes in Multipsk. 73 Patrick - Original Message - From: Tony To: digitalradio@yahoogroups.com Sent: Saturday, April 21, 2007 9:25 AM Subject: [digitalradio] Path Simulator tests -- JT65A vs Olivia and others All: I used Pathsim to compare the sensitivity of JT65A vs MFSK, PSK31 and OLIVIA using AWGN to alter the SNR. I ran direct-path with no ionospheric disturbance. The chat modes decoded with error-free print down to -12 to -14db SNR. The JT65A mode decoded at -27db SNR (signal inaudible). Assuming the Pathsim white noise measurments were accurate, I think it's safte to say that JT65 is capable of decoding much weaker signals than the others. Would be interesting to see how it does with simulated ionospheric disturbances. 73 Tony - KT2Q
Re: [digitalradio] S/N Multipsk figures -- JT65A vs Olivia and others
Hi Patrick, Are you thinking about incorporate J65A in Multipsk? It would be great LA5VNA Steinar Patrick Lindecker wrote: Hello to all, _Comparizon with S/N Multipsk figures._ According to JT65 specifications, this mode decodes with few errors down to -23 dB, with a normalized band of 2.5 KHz. All Multipsk figures are normalized with a band of 3 KHz. -23 dB in 2.5 KHz is about -24 dB in 3 KHz band (-23.792 dB exactly). This figure of -24 dB can be compared to Olivia 250-8 which has a minimum S/N of -14 dB. So JT65 is 10 dB better or 10 times better. But of course JT65 is much slower that Olivia 250-8. The only modes which are close to JT65 are: * THROBX: Lowest S/N: -18,5 dB for the 1 baud, -17.5 dB for the 2 bauds * PSKAM10: Lowest S/N : -19.5 dB In conclusion JT65 is better (under S/N criteria) that any modes in Multipsk. 73 Patrick - Original Message - *From:* Tony mailto:[EMAIL PROTECTED] *To:* digitalradio@yahoogroups.com mailto:digitalradio@yahoogroups.com *Sent:* Saturday, April 21, 2007 9:25 AM *Subject:* [digitalradio] Path Simulator tests -- JT65A vs Olivia and others All: I used Pathsim to compare the sensitivity of JT65A vs MFSK, PSK31 and OLIVIA using AWGN to alter the SNR. I ran direct-path with no ionospheric disturbance. The chat modes decoded with error-free print down to -12 to -14db SNR. The JT65A mode decoded at -27db SNR (signal inaudible). Assuming the Pathsim white noise measurments were accurate, I think it's safte to say that JT65 is capable of decoding much weaker signals than the others. Would be interesting to see how it does with simulated ionospheric disturbances. 73 Tony - KT2Q
Re: [digitalradio] S/N Multipsk figures -- JT65A vs Olivia and others
Hello Steinar, The problem in JT65 is that the important part of the Reed Solomon coding/decoding (RS tables...) is not described. Moreover, it is writen in the JT65 specifications (about RS decoding): it is based on a research paper by Ralf Koetter and Alexander Vardy and uses computer code licenced from this company, CodeVector Technologies It can be understood as the soft-decison decoding of Reed-Solomon algorithms are at present in the research domain. I think to (perhaps) do in the (far) future a -30 dB S/N mode, based on as something similar to RS ID but slower, with an exchange limited to a call (6 characters) and some other additive bits. 73 Patrick - Original Message - From: Steinar Aanesland To: digitalradio@yahoogroups.com Sent: Saturday, April 21, 2007 11:17 AM Subject: Re: [digitalradio] S/N Multipsk figures -- JT65A vs Olivia and others Hi Patrick, Are you thinking about incorporate J65A in Multipsk? It would be great LA5VNA Steinar Patrick Lindecker wrote: Hello to all, _Comparizon with S/N Multipsk figures._ According to JT65 specifications, this mode decodes with few errors down to -23 dB, with a normalized band of 2.5 KHz. All Multipsk figures are normalized with a band of 3 KHz. -23 dB in 2.5 KHz is about -24 dB in 3 KHz band (-23.792 dB exactly). This figure of -24 dB can be compared to Olivia 250-8 which has a minimum S/N of -14 dB. So JT65 is 10 dB better or 10 times better. But of course JT65 is much slower that Olivia 250-8. The only modes which are close to JT65 are: * THROBX: Lowest S/N: -18,5 dB for the 1 baud, -17.5 dB for the 2 bauds * PSKAM10: Lowest S/N : -19.5 dB In conclusion JT65 is better (under S/N criteria) that any modes in Multipsk. 73 Patrick - Original Message - *From:* Tony mailto:[EMAIL PROTECTED] *To:* digitalradio@yahoogroups.com mailto:digitalradio@yahoogroups.com *Sent:* Saturday, April 21, 2007 9:25 AM *Subject:* [digitalradio] Path Simulator tests -- JT65A vs Olivia and others All: I used Pathsim to compare the sensitivity of JT65A vs MFSK, PSK31 and OLIVIA using AWGN to alter the SNR. I ran direct-path with no ionospheric disturbance. The chat modes decoded with error-free print down to -12 to -14db SNR. The JT65A mode decoded at -27db SNR (signal inaudible). Assuming the Pathsim white noise measurments were accurate, I think it's safte to say that JT65 is capable of decoding much weaker signals than the others. Would be interesting to see how it does with simulated ionospheric disturbances. 73 Tony - KT2Q
