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[aprssig] Delayed packets (yet again)

Tim Cunningham tim_cunningham at mindspring.com
Sat Aug 26 01:18:17 UTC 2006

There was a delayed packet discussion specifically concerning IGates recently. We did a through study into the problem in my area and isolated the problem to a UI-View station operating as an IGate. Since that discussion there were a few other folks across the country who wrote off-line that they experienced the same issue with UI-View in their areas. This issue was specifically limited to a UI-View IGate that was injecting packets greater than 1 minute later than another IGate using APRS+SA. Many of the packets were time stamped to verify the delay. It was not a digipeater delay because we could see two IGates hearing the same packet from the same digipeater being injected into the APRS-IS greater than one minute apart.

IGates that are experiencing delays should consider using filtered port 14580 and limit their data to under 100 to 200km using the m/100 to m/200 qualifier. When an IGate tries to process the full feed they are going to run slower depending on their computer configuration and whether they are using a dial-up feed or a high speed link.

There are many sources of delays that also include digipeaters. The first step is to identify if the delay is the USB to serial converter which should be fairly easy by visual observation on how long it takes a decoded packet to appear on the screen. Then, it becomes only a measure of time from that point to when it appears on the APRS-IS.

Tim - N8DEU
Huntsville, Alabama

  ----- Original Message ----- 
  From: J T 
  To: TAPR APRS Mailing List 
  Sent: Friday, August 25, 2006 1:26 PM
  Subject: [aprssig] Delayed packets (yet again)

  In one of the many "delayed packet" discussions there was talk about some serial-to-USB converters causing issues.  I can't seem to find this discussion in the archives.  Does anyone recall the make(s)/model(s) of the serial-to-USB converters that are known or suspected of being problematic?  And perhaps suggest a model that is known to work well?

  I've been communicating with an I-gate owner whose station is injecting delayed packets into APRS-IS.  He's too busy to study and fix the problem (unfortunately for the rest of us) so I'm trying to help gather some information that may make it easier to debug the problem.  He swapped TNCs but that didn't fix it.  He mentioned that he uses a serial-to-USB converter so hopefully I can talk him into experimenting with a different one or coming up with another solution.

  -Jerome, W0JRT

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