[aprssig] PSAT & igating and Optimum antenna

Steve Dimse steve at dimse.com
Sun Jun 7 13:38:31 EDT 2015

On Jun 7, 2015, at 9:55 AM, Max Harper via aprssig <aprssig at tapr.org> wrote:

> Another problem (if you ask me) is that when you send a beacon, and that beacon gets digi'ed, and your own station recieves it back and igates it, the station that digi'ed it gets stripped out of the packet.
> This beacon is set to go out via 'RF only' but looks like is was sent direct to the APRS-IS. Also note the time stamp at the beginning of the payload as well as the timestamp from findu showing 5 seconds difference. There was one or more digi's in there
> 20150607070734,KG4PID-14>APRX28,TCPIP*,qAC,T2TEXAS:/070729h3417.45N/08742.32W#PHG7250 Bear Creek, Al

This is the dup check issue already discussed. Regardless of whether you intended to send it RF only, if the path says TCPIP* it was sent directly to the APRS-IS, it was not IGated from RF. The q construct confirms it was a direct to internet packet. The path was not changed, it was the direct to internet packet which reached findU first (no surprise), somewhere along the line any RF IGated packets were removed by dup check.

You are connected to a tier 2 server, so the packet travelled through a number of servers before it got to findU, each can add a few tenths of a second of latency. The order in which a program performs tasks also gets involved. findU timestamps are not a reliable way to determine RF propagation time, or in this case to try to prove RF propagation occurred. 

Steve K4HG

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