Friday, January 4, 2008

APRS digipeater path adviser



The station info page now gives some feedback and advice on APRS digipeater path settings. It approves paths which request less than 4 digipeaters and suggests paths which have 2 digipeaters (WIDE2-2 or WIDE1-1,WIDE2-1 or TRACE2-2). It also gives advice on invalid usage of RELAY and WIDE1-1 when they're not the first component of the path, and suggests replacing RELAY with WIDE.

There are different opinions on "good" settings, and there are regional differences too. I believe the settings offered are good for most environments. It doesn't really matter so much if one uses TRACE or WIDE, as long as the total amount of digipeaters isn't very large. 2 is good in areas with good coverage digipeaters and igates, 3 is usually good elsewhere. 5, 6 or 7 is, well, not good.

3 comments:

pa3bwe said...

Excellent tool !

Anonymous said...

I'm about to fly an airborne tracker for the first time at altitudes up to 7000 ft. I was advised to use WIDE2-1 as the path. Hopefully that is acceptable.

One of my goals is to figure out how far out my tracker is being received to reduce interference. I imagine the only way to figure that out would be to have access to the raw data from the APRS-IS servers, presumably before it's filtered for dups. Do you have access to that raw data in the APRS-IS feed or do they simply not report the dups?

Thanks for an awesome site. 73 de Doug, N2WOL

oh7lzb said...

WIDE2-1 should be OK, it'll be digipeated a few times because a lot of digipeaters will hear your packets, but at least it's not propagated to further digipeaters.

All of the APRS-IS servers remove duplicate packets, so any system which connects to the APRS-IS to receive these packets, usually receive only a single copy of a packet. So no, I have no way to say for sure, which igates or digipeaters got your packets.

Because multiple igates are likely to hear your packets directly at the same time, one packet will probably go via one igate, and the next one via another, so that you'll get some idea of the coverage.

The duplicate filtering isn't perfect, though - the APRS-IS servers (javaprssrvr mostly) only filter duplicates over a rather short time (30 seconds, I think), so if there's a longer delay (due to a long or slow digipeater path, or a bad connection between igate and the APRS-IS), some duplicates will get through. aprs.fi will then try to do it's best to filter those out.