December 2014 – Page 2 – owenduffy.net

An example of Eb/N0 design with the Field strength / receive power converter

I have been asked whether the Field strength / receive power converter can be used to solve a Eb/N0 (E_b/N₀) design problem.

Eb/N0 is a method often used for specifying the relationship of signal and noise that will give adequate bit error rate in a data demodulator.

Whilst the calculator was not specifically designed for that purpose, and you cannot directly enter the desired Eb/N0, with the help of a hand calculator for simple calculations, a solution can be found. Continue reading An example of Eb/N0 design with the Field strength / receive power converter

Last update: 9th December, 2014, 8:50 AM

Exploitation of NEC’s GM card

NEC-2 and NEC-4 support a GM card to translate and rotate a structure in three dimensions.

This article gives a simple but practical example of exploitation of this often overlooked facility. Continue reading Exploitation of NEC’s GM card

Last update: 5th December, 2014, 2:44 PM

Packet loss by digi collision

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

Last update: 1st December, 2014, 4:16 PM

Another Argent Data T3 incompatibility

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

Last update: 1st December, 2014, 4:17 PM