Hello Rick, >I think the main thing I am asking is ... how long a window do you need? >Pactor uses a 170 ms. idle time. Since the timing from a computer (20 >ms maximum error) is not able to switch a transceiver fast enough for >Pactor, would 20 times longer than the maximum error be enough? Ergo, >20 x 20 ms = 400 ms window or idle time? The problem is the time at which you sample the bits (which lasts only 10 ms). The only solution for a Windows PC would be an "almost synchronous ARQ mode" as suggested before, taking example into the Scamp. It means that you don't know exactly when the signal will come. You will have to try to "symbol synchronize" and watch for the the expected signal you are waiting for, through a given prefix you must decode first. Of course, perhaps 6 symbols or more (synchronization + prefix) will be lost compared to a true ARQ mode, but the difference of timing could be very small.
73 Patrick 73 Patrick ----- Original Message ----- From: KV9U To: digitalradio@yahoogroups.com Sent: Friday, September 15, 2006 3:39 AM Subject: Re: [digitalradio] Re: ARQ sound card modes It is kind of ironic that MS-OS and Linux-OS are further from Real Time OS's than the older software. But even with a +/- 10 ms time (worst case 20 ms from one extreme to the other), wouldn't you just have to have a little bit longer "window" than existing ARQ modes in order to succeed? I think the main thing I am asking is ... how long a window do you need? Pactor uses a 170 ms. idle time. Since the timing from a computer (20 ms maximum error) is not able to switch a transceiver fast enough for Pactor, would 20 times longer than the maximum error be enough? Ergo, 20 x 20 ms = 400 ms window or idle time? 73, Rick, KV9U Patrick Lindecker wrote: >Hello, > >When we were on MS-DOS PC (good old time HI), the clock (and all the hardware in fact) was accessible by program (through registers) and it was easy to determine the error of the PC cristal. I measured in several MS-DOS PC an error of more or less 1/3000, which was not very good, but I suppose it was not really indipensable to be precise for a PC. >I suppose that the modern PC have the same relative uncertainty. > >I have seen, thanks to Sholto G7TMG, that under Windows the time can be very precise (down to 100 nanoseconds) but only 64 times by second, and there is no interpolation between each sample. So the uncertainty in a Windows PC is +/- 7.81ms which rules out ARQ Pactor and Amtor in a Windows PC. > > 73 >Patrick > > > [Non-text portions of this message have been removed] 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/ <*> 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/
