Can you explain how it is that you can run a symbol rate of 2400 (baud) with 188-110A and it works very well running at this extremely high speed for HF? And yet other modes, such as Packet, don't work very well at 300 baud, and Walt has pointed out that government studies had show that under 50 baud was about the optimum for the types of conditions we often find on HF?
Why would we not just increase the baud rate of MT-63 or MFSK16 to get a similar speed boost if it can work that well? How tight do you need the frequency tolerance to be to enhance weak signal modes? The ICOM Pro rigs run at around 0.5 ppm, which seems several orders of magnitude better than what some of the digital mode programs require. I wonder how much better a weak signal/difficult condition mode we could come up with if there was a tighter frequency tolerance. You might recall the early developement of Clover I, by Ray, W7GHM. If I remember right, the signal was phaselocked to WWV or other time standard frequency. Later this was abandoned with DSP developed as a bus card and the computer mostly being used as a dumb terminal, but it will never be as tight a frequency tolerance as 10 e -6 or so:) 73, Rick, KV9U Steve Hajducek wrote: >Hi Rick, > >ALE itself is 8FSK, 125 baud, all protocols on that modem. > >After an ALE link, any protocol, be it an ALE 8FSK or other can be >utilized via other modems. Built into PC-ALE/MARS-ALE is a >MIL-STD-188-110 modem, MARS-ALE also actively supports external >TNC/Modems. PC-ALE passive provides this support as well using any >third party program. > >The MIL-STD-188-110A serial tone modem is just that, a single PSK >carrier frequency that by the standard is locked at 1800hz using a >constant 2400bps Symbol Rate. Then coded data rates from 75-2400bps >and 4800bps un-coded, this is what is supported by PC-ALE. MARS-ALE >supports 1200hz, 1500hz and 1800hz selections for the PSK carrier and >a symbol rate as low as 1600bps (the only one that can be used with >the 1200hz PSK carrier) to achieved lesser IF BW requirements from >the standard 300-3300hz (3Khz). I could not make less than a 1600bps >symbol rate work when I last was focused on that modem. Later >standards and newer versions of '188-110 and DLP's and waveforms that >have developed that are implemented in new hardware are much faster >and some modems will auto adjust to different PSK carriers and symbol >rates I have learned. At present in MARS we have all the speed we >need with the 2400bps coded until faster CPU's come along and more >consistent external PCSDM's are used by all stations and radios with >better frequency accuracy and stability are being used. > >/s/ Steve, N2CKH/AAR2EY > > > > 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/
