[aprssig] Why do we not use APRS 9600?

Andrew Pavlin spam8mybrain at yahoo.com
Wed Feb 16 16:56:48 EST 2022

 Mostly because of the huge existing user base of non-APRS-enabled radios using mike&speaker connections to a TNC, which means they are not capable of the audio quality needed for 9600. Plus all of those existing digis and I-gates would have to be overhauled (even if their existing hardware is capable of 9600) just to reconfigure them, which means that all of those 1200-only stations quit working. To allow both 1200 and 9600 to co-exist, we would need to establish another frequency for the 9600-baud usage, and set up new digipeaters and I-gates on that frequency and baud rate (it would be difficult for them to co-exist with the 1200-baud stations because of desense and intermod issues at the sites, unless we put the 9600-baud channel on a totally different band, such as 70cm). Remember, we hams don't believe in planned obsolescence; we keep equipment running _far_ past the end-of-warranty or scheduled end-of-life. :-)

Also, WB2OSZ has written a useful whitepaper explaining why 9600 baud is not significantly faster than 1200 baud, so we might get a doubling of throughput at best with the baud rate change, mostly due to preamble/postamble time and lousy TXDELAY capabilities of the radios in use.
direwolf/Why-is-9600-only-twice-as-fast-as-1200.pdf at master · wb2osz/direwolf

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direwolf/Why-is-9600-only-twice-as-fast-as-1200.pdf at master · wb2osz/d...

Dire Wolf is a software "soundcard" AX.25 packet modem/TNC and APRS encoder/decoder. It can be used stand-alone ...



So are you prepared to tell every APRS-using ham to junk their-1200-baud-only gear and buy replacements and reconfigure their existing gear to 9600-baud amid the screams of outrage from the portion of the digipeater/I-gate user bases who don't listen to your mandate? :-)
It's a nice dream, but it will have to happen by gradual transition and fading away of the old 1200-baud gear. Which probably isn't going to happen since there are other means (like AREDN and LoRA) to get significantly faster than 9600 baud. Just not enough return on investment.
Just be thankful those Canadian hams back in the 1980's who effectively set the baud rate standard didn't end up with a pile of Bell 103 modems instead of 202's. :-)

Andrew, KA2DDO

    On Wednesday, February 16, 2022, 04:38:01 PM EST, Jonathan Delaney <kb3osp at gmail.com> wrote:  
  The  discussion  this  past  week  has  made  me  wonder  on  why  APRS  9600  is  not  used.  To  my  knowledge  most  if  not  all  APRS  mobile/ handheld enabled  radios  have  a  TNC  capable  of  9600  bps  however  we  still  set  them  to  1200.  Is  this  because  most  of  the  digis  and  igates  still  use  1200?  What  would  it  take  to  get  everyone  to  change  to  9600?
 Jon  KB3OSP
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