and... "JT65 transmits messages using 65-tone frequency-shift keying at 2.7 baud. The lowest tone at 1270.5 Hz is used to establish time and frequency synchronization; it is switched on for half of the time, according to a pseudo-random on-off pattern. The remaining tone intervals carry the user message, using a Reed-Solomon code for forward error correction. The three JT65 submodes all use the same code and modulation scheme, but the spacing between tones is different—approximately 2.7, 5.4, and 10.7 Hz for modes A, B, and C, respectively. A transmission in one submode must be received in the same submode. If the equipment and propagation path are stable enough that the measured width of the sync tone is consistently 4 Hz or less, JT65A will be about 1 dB more sensitive than mode B and 2 dB more sensitive than C. Shorthand JT65 transmissions consist of alternating tones, each lasting 1.486 s. The lower of the two frequencies is always at the sync-tone frequency, 1270.5 Hz, and the separation between tones is given in the following table: Message JT65A JT65B JT65C ATT 26.9 Hz 53.8 107.7 Hz RO 53.8 107.7 Hz 215.3 RRR 80.8 161.5 323.0 73 107.7 215.3 430.7 " On 4/4/07, KT2Q <[EMAIL PROTECTED]> wrote: > > > > > > > > Does anyone know the actual transmit bandwidth > > of J65A? It would appear to be > > about 2 KHz wide. > > Its roughly 200hz wide -- see attached. > > Tony KT2Q > >
-- Andy K3UK Skype Me : callto://andyobrien73 www.obriensweb.com Announce your digital presence via our DX Cluster telnet://cluster.dynalias.org Our other groups: http://groups.yahoo.com/group/dxlist/ http://groups.yahoo.com/group/themixwgroup http://groups.yahoo.com/group/contesting http://groups.yahoo.com/group/wnyar http://groups.yahoo.com/group/Omnibus97 Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
