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16788Re: [tracker2] 1-persistence

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  • owenvk
    Aug 17 5:38 PM
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      If more than one digi can hear a transmitter, then you have the scenario for a packet from that transmitter causing collision as all of the digis decoding it and using 1-persistence transmit simulaneously.The p-persistence IS a mechanism for reducing the risk of collision by reducing the probability that all n digis transmit simultaneously... but somebody got the idea that collision was a network virtue.A long time ago in AX.25 networking, 1-persistence was regarded as aggressive and unsocialbe.Contrary to James comment, no I am not new to APRS, AX.25, or X.25... and Jason, I don't share your view that the future of APRS is rosy... in this part of the world it is crippled with traffic that is relevant to few and compromises its capacity to do position reporting.Hams crippled packet networks by loading them up with zip files of shareware that few people wanted, preventing the network having reasonable interactive response, preventing the network handling even email in a timely way.More than ten years ago, I conducted extensive experiments with APRS, but the national infrastructure in my part of the world was totally bogged by iGated traffic driving channel utilisation above 50%... just so people could see the world on UIVIEW via radio.In my current environment, I hear two very strong digis (<20km distance to each), and often another at 190km, all on prominent hills. One has pre-emphasis and 1.5kHz deviation, the others no pre-emphasis (probably by virtue of gross overdrive) and 6 and 10kHz deviation. These are used as examples by hams to configure their own systems.After more than 30 years we cannot agree on whether pre-emphasis should be mandatory on VHK AFSK FS Ham202. Sure the mixed environment works with some performance degradation, and we cannot now lay down 'standards' because it will alienate either most existing users or Kenwood.APRS is very loosely organised choas and anarchy... like most of ham radio.In search of a digis that are complete implementations, proven to be reliable, consistently don't suffer latency of more than seconds,and decode everthing including the very popular TinyTrak1/Foxtrak, I don't see any modern 8 bit microcontroller solutions, or even 32 bit ones... UIDIGI on a Z80 still sets a standard to be achieved.Owen
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