Michael, Thank you for the elucidation. I am certainly no expert in all this! Not uneducated, but not expert and easy to get confused between baud and bit rate when trying to explain it.
Your consise explanation is appreciated. Jim WA0LYK --- In digitalradio@yahoogroups.com, Michael Keane K1MK <[EMAIL PROTECTED]> wrote: > > At 09:33 AM 2/4/06, jgorman01 wrote: > >1. I don't know why you say US hams cannot experiment on HF unless our > >regs are changed. We currently have minimal bandwidth regulations. > >Someone is certainly welcome to correct me, but I don't know of any HF > >modem that tries to use 2 tones at 300 baud or higher. They all use > >multiple tone modems and modulate individual pairs at a substantially > >lower baud rate. Like 12 tone pairs, each at a rate of 60 baud which > >give an equivalent rate of 720 baud, substantially over the 300 baud > >regulation. > > To help avoid the confusion that seems to creep in when talking about > "bauds," for the example given, the state of each of the twelve > binary sub-carriers represents one bit of the symbol being > transmitted. That's one 12-bit symbol that changes state 60 times a > second; the symbol rate is 60 symbols per second while the data rate > is 720 bits per seconds. The rules put a limit on symbol rate that > can be used not the bit rate that can be achieved. > > Inter-symbol interference due to delay spread from fading/multipath > makes the restriction to a maximum symbol rate 300 baud a phantom limit at HF. > > Using DV as an example, the AOR modem sends a bit stream at a rate of > 3200 bits per second using a symbol rate of 50 symbols per second; > the various DRM modes send a comparable speeds with a maximum symbol > rate is 37.5 symbols per seconds. > > Olivia (which is m-ary FSK and not multiple sub-carriers) includes a > two tone configuration with symbol rates of 500 or 1000 symbols per > second; the utility of that at HF is quite dubious. > > 73, > Mike K1MK > > Michael Keane K1MK > [EMAIL PROTECTED] > Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> 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/
