Sam Buchanan
been here awhile
Poking through the aprs.fi blog revealed a new filter feature that has been added to the server software:
"In addition to the old filtering methods, out-of-order and duplicate packets are now filtered using APRS timestamps embedded in the packets. If a packet comes in that has an older timestamp than the previous packet, it is promptly discarded. This should be a very effective duplicate filter when timestamps are transmitted by the tracker."
This may very well take care of most of the "red error" packets we sometimes see due to digis and iGates buffering packets. It will, however, require a small programming change on our tracker.
In order to activate time stamps in the tracker, MIC-E encoding must be turned off. This isn't a problem, I've been tracking successfully without MIC-E for a couple of years. This means your packet will be a few micro-seconds longer in duration since the position reports will not be compressed via the MIC-E protocol. The upside, besides supporting time stamps, is that you can see the actual position report in each packet in plain language.
Here is an example of an uncompressed packet from my tracker:
2011-08-06 11:19:27 CDT: N399SB>APT311,WIDE2-1,qAR,KI4GVH-1:!3420.36N/08652.48W'168/147/A=002706/KJ4CKK
Notice the text which I bolded that shows lat/long, speed, altitude and callsign in plain language instead of the usual MIC-E generated weird symbols. Cool!
When you uncheck MIC-E, check the "Timestamp HMS" box in the configuration window:
Might as well go ahead and check "Only Send Valid" while you are at it. This will prevent the tracker from sending GPS data that is corrupted or incomplete.
By the way, I have my tracker set to transmit the Status Text (which is my FCC callsign) every packet so the aprs police can't accuse me of not ID'ing my tracker properly.
Timestamp HMS stands for hour, minute, second. MIC-E must be disabled because time stamps can't be transmitted via MIC-E compression.
I haven't had a chance to add timestamping to my tracker yet but will do so as soon as possible. This should eliminate the packet errors from buffered packets. Let's give it a try and see how it works. This could be a huge upgrade in the reliability of our tracks.
"In addition to the old filtering methods, out-of-order and duplicate packets are now filtered using APRS timestamps embedded in the packets. If a packet comes in that has an older timestamp than the previous packet, it is promptly discarded. This should be a very effective duplicate filter when timestamps are transmitted by the tracker."
This may very well take care of most of the "red error" packets we sometimes see due to digis and iGates buffering packets. It will, however, require a small programming change on our tracker.
In order to activate time stamps in the tracker, MIC-E encoding must be turned off. This isn't a problem, I've been tracking successfully without MIC-E for a couple of years. This means your packet will be a few micro-seconds longer in duration since the position reports will not be compressed via the MIC-E protocol. The upside, besides supporting time stamps, is that you can see the actual position report in each packet in plain language.
Here is an example of an uncompressed packet from my tracker:
2011-08-06 11:19:27 CDT: N399SB>APT311,WIDE2-1,qAR,KI4GVH-1:!3420.36N/08652.48W'168/147/A=002706/KJ4CKK
Notice the text which I bolded that shows lat/long, speed, altitude and callsign in plain language instead of the usual MIC-E generated weird symbols. Cool!
When you uncheck MIC-E, check the "Timestamp HMS" box in the configuration window:
Might as well go ahead and check "Only Send Valid" while you are at it. This will prevent the tracker from sending GPS data that is corrupted or incomplete.
By the way, I have my tracker set to transmit the Status Text (which is my FCC callsign) every packet so the aprs police can't accuse me of not ID'ing my tracker properly.
Timestamp HMS stands for hour, minute, second. MIC-E must be disabled because time stamps can't be transmitted via MIC-E compression.
I haven't had a chance to add timestamping to my tracker yet but will do so as soon as possible. This should eliminate the packet errors from buffered packets. Let's give it a try and see how it works. This could be a huge upgrade in the reliability of our tracks.
Last edited:
