Loading ...
Sorry, an error occurred while loading the content.

Re: [Q15X25] QRM

Expand Messages
  • Mark Miller
    ... Russ, Yes increasing the interleave seems to increase the packet size. Interleaving by itself is good for a QSB channel. Interleaving is one of the
    Message 1 of 6 , Dec 19, 2002
    • 0 Attachment
      At 12:46 12/19/02 -0500, you wrote:

      >I tried an interleave of 16 but went back to 8 as I noticed that my packets
      >became noticeably longer with the same amount of text typed.


      Russ,

      Yes increasing the interleave seems to increase the packet
      size. Interleaving by itself is good for a QSB channel. Interleaving is
      one of the parameters that makes MT63 so robust. There must be some
      redundancy in bits along with the interleaving in Q15X25, because
      interleaving alone does not increase the packet size. Higher S/N ratio is
      always good.

      Mark Miller
    • Mark Miller
      I think the 20M band is dead right now. 14.115 USB might be a good choice. I will hang out there and listen for a while. 73 Mark N5RFX
      Message 2 of 6 , Dec 19, 2002
      • 0 Attachment
        I think the 20M band is dead right now. 14.115 USB might be a good
        choice. I will hang out there and listen for a while.

        73
        Mark N5RFX


        At 18:40 12/19/02 +0000, you wrote:
        >Let me know how 14113 does. I'm currently beaconing on 14103 Lower
        >every ten minnutes but I'll switch up to 113 if that works out.
        >
        >Dave
        >
        >
        >
        >To unsubscribe from this group, send an email to:
        >Q15X25-unsubscribe@yahoogroups.com
        >
        >
        >
        >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
      • tpmannin <tpm@prkele.tky.hut.fi>
        Hi all, I just joined here as well... ... True. The interleaver implementation in Q15X25 is a compromise. It is a simple self synchronizing interleaver, which
        Message 3 of 6 , Dec 20, 2002
        • 0 Attachment
          Hi all,

          I just joined here as well...

          > Yes increasing the interleave seems to increase the packet
          > size. Interleaving by itself is good for a QSB channel.
          > Interleaving is
          > one of the parameters that makes MT63 so robust. There must be some
          > redundancy in bits along with the interleaving in Q15X25, because
          > interleaving alone does not increase the packet size.

          True. The interleaver implementation in Q15X25 is a compromise.
          It is a simple self synchronizing interleaver, which makes things
          easy but has the drawback of requiring rather long flushing.
          The flushing is done with zeroes so it's completely wasted power...

          This behaviour is seen nicely in the upper picture at

          http://people.wiesbaden.netsurf.de/~signals/FFT/Q15X25.HTML

          You can see how the interleaver first needs to be filled at the
          start (after preamble) and then flushed at the end (the very last
          part is the end-of-drame postamble). Increasing interleaving
          makes the straight lines (sending zeroes) in the data part longer.

          The same thing applies to MT63 by the way. The long latency in
          MT63 is caused by exactly the same issue.

          /Tomi OH2BNS
        Your message has been successfully submitted and would be delivered to recipients shortly.