A drive test of the OpenLog logger collecting raw NMEA data in parallel with the TinyTrak (VHF) was conducted. To maximise the performance of APRS, a fill-in digi / iGate was run at my home. The tracker used a 65W transmitter with quarter wave vertical in the centre of the car roof.
defect ridden iGates that lose, duplicate and corrupt packets;
poorly configured mobiles;
network congestion and interference;
unpredictable equipment failures;
basic geographical coverage of the network; and
dependence on the ionosphere for HF APRS.
This article describes an enhancement to the popular TinyTrak (and its clones) to also capture the GPS stream to an inexpensive local data logger.
The logger does not interfere with normal radio APRS, it coexists with it and creates a properly timestamped fine detail log of positions over a very long time, a log that can be post processed into a range of graphic / map and tabular reports.
The datalogger used in an OpenLog. It is a simple logger that writes data to a micro SD card, costs about $A12 (inc post) for the logger and about A$10 (inc post) for a 16GB Class 10 micro SD card. (A slower card could be used, but they aren’t much cheaper.)
Adjusting KISS TNC AFSK tx level using an isochronous test packet explained a technique to drive a KISS TNC with a specially constructed packet that contains an ISOCHRONOUS test packet, a packet that will produce equal high and low tone alternation in the transmitted AFSK signal. The improved packet should be repeated by most digipeaters, allowing observation of their modulation performance.
The message “ashim at shell servo” must be an important one.
I have heard VK2UBQ-9 sending this message to VK2XSO-5 for many months, a couple of hundred times a day when VK2UBQ-9 has his radio switched on.
The intended recipient was last reported on aprs.fi in May 2014, seven months ago, yet the APRS system is still wasting bandwidth trying to deliver this message, presumably waiting for a delivery acknowledgement. Continue reading ashim at shell servo
It has been apparent to me that the two local digipeaters often collide.
One uses UIDIGI and therefore is conformant with the p-persistence channel access algorithm.
The other is a Argent Data T3-135 which does its own thing.
To discover how many packets are detected with bad CRC, I installed 6PACK on a TNC. 6PACK reports receive CRC failures which are logged by the Linux kernel. Data was collected for seven hours through the middle of the day to ensure that there was traffic, but that channel utilisation was low. Continue reading Packet loss by digi collision
I have written on incompatibility of Argent Data TNCs with other devices.
In pursuing apparent packet loss, I have run up a Paccomm Tiny-2 MK-2 TNC with 6PACK firmware, and my aprx server using Linux AX25 kernel support and 6PACK driver.
It has become apparent that although the system reliably decodes packets from a multi-packet burst from VK2AMW-1, it only ever decodes the first packet of a multi-packet burst from VK2RHR-1. Frame check errors are logged. Continue reading Another Argent Data T3 incompatibility