Hello Votjech, >spectrogram it seems to be some kind of MFSK modulation, always the Yes it is.
>list. I suppose that the RS ID is very similar to Olivia, there are It is very similar to JT65A in fact. >- Olivia uses Hadamard/Welsh transformation, RS uses Reed Solomon block code Yes it does >- Olivia is decoded parallel on a constraned band, RS is decoded parallel on the whole sound card spectrum. The channel separation is half tone. No, when searching for an Olivia or RS ID transmission, the goal is to find the best correlation with a possible code. Half tone after half tone, you calculate the functions and see if the result fits with a possible transmission of code. The big advantage of these functions (Hadamard or RS) is that the correlation function is extremely sharp. - RS code sends just one block with the mode ID. Yes it does. 73 Patrick ----- Original Message ----- From: Vojtech Bubnik To: digitalradio@yahoogroups.com Sent: Thursday, April 05, 2007 8:24 AM Subject: [digitalradio] Re: Reed Solomon Identifier Hi Patrick. > >you send a heavily FEC protected keyword in the desired mode. > >you do a parallel decode of all modes, de-FEC all and look which one > >matches the the codeword ? > Yes it is. But it is not only done for one frequency, it is done for all frequencies in the band. I played with MultiPSK and listened to the generated RS sequence. In my opinion it is always the same modulation. According to my ears and spectrogram it seems to be some kind of MFSK modulation, always the same number of tones and symbol speed. Please correct me, but I think there is a misunderstanding on the list. I suppose that the RS ID is very similar to Olivia, there are three differences though and I thing we have discussed it by personal e-mails. - Olivia uses Hadamard/Welsh transformation, RS uses Reed Solomon block code - Olivia is decoded parallel on a constraned band, RS is decoded parallel on the whole sound card spectrum. The channel separation is half tone. - RS code sends just one block with the mode ID. Olivia and RS decode both a lot of channels in parallel (at least the original Olivia code from Pawel Jalocha does that) and it selects the one, which gives highest correlation. This automatically gives the answer for other party frequency. I received the RS code from Patrick, but I did not add it to PocketDigi yet. I am busy now with firmware programming of ATS-3A, I hope to teach it to modulate the single tone modes by programming its DDS. It will be the ultimate portable digital set, hi. 73, Vojtech OK1IAK
