An important element of early AX.25 networks was the Terminal Node Controller (TNC). Essentially, a TNC was a packet assembler / disassembler (PAD) pretty much equivalent to the PAD of X.25 networks but adapted to AX.25, and commonly, an embedded modem.
The TNC-2 was a hardware configuration which became a de-facto standard, and various firmware packages became available each with their own advantages and disadvantages. and a range of protocols for the host connection.
One of the inventions was the KISS protocol (KISS for keep it simple stupid) from Mike Chepponis (K3MC) & Phil Karn (KA9Q), and an implementation for TNC-2. Continue reading The KISS TNC – too simple, too stupid?
Chameleon has announced a small transmitting loop, the Chameleon CHA M-LOOP. Continue reading Chameleon CHA M-LOOP
I have posted several articles on headless APRS servers based on RPi. This article describes one based on RPi, AX25 soundmodem using a $2 USB sound card, and aprx v2.09.
Above is the server hardware. It uses the Sailer sound modem and kernel AX.25 support. This is currently configured as a RX only iGate for 30m, hence no tx audio path and no PTT (though on HF, PTT can be done simply using transceiver VOX). The small black USB module is a Belkin WLAN adapter. Continue reading RPi headless aprx server using soundmodem
I have a bit of a soft spot for the Diamond X-50N. It is a fairly rugged vertical for 2m/70cm. Though I live in a rural setting, I resist the temptation of high gain antennas of this type as they tend to suffer fatigue problems resulting in noise in quick time, whereas the rigid one piece X-50 seems to last and last (I have another that must have had 25 years outdoor service).
The X-50N is mounted on a telescopic steel mast at 11m at its base, and fed with 10m of LDF4-50A to the antenna entrance panel, and 2m of LMR-400 to the radio. The XN50N has three short radials which are visible in the pic above, but somewhat obscured by a fan of four upwards pointing wires to discourage birds perching on the gibbert for the G5RV. Continue reading Diamond X-50N #2 at VK2OMD
This article shows use of Lou Destefano’s (VK3AQZ) VK3AQZ RF power meter (RFPM1) to adjust the output power of a low power transmitter.
Above, the test setup used. Continue reading VK3AQZ RF power meter (RFPM1) – adjust Tx power example
This article shows use of Lou Destefano’s (VK3AQZ) VK3AQZ RF power meter (RFPM1) to plot the response of a 144MHz filter.
Above, the RFPM1 as used.
Above, the test setup. The filter (DUT) is connected between a standard signal generator (SSG), and the RFPM1 connected to the filter output. A DVM recorded the DC voltage on the ‘CAL’ terminals of the RFPM1. A series of measurements was made from 140 to 148MHz and the results calculated and plotted in Excel. Continue reading VK3AQZ RF power meter (RFPM1) – filter response example
In the past, I have recommended FTDI based USB-RS232 adapters strongly because of their reliability and compatibility, albeit at a price. Continue reading FTDIgate and revokation of my previous unqualified recommendation for FTDI
This article documents my build of Lou Destefano’s (VK3AQZ) RF Power Meter kit.
The power meter is based on probes using an AD8307 logarithmic detector.
Above, the RF Power meter with two probes. (The ferrite sleeves were not part of the kit.) Continue reading VK3AQZ RF power meter (RFPM1)
I had cause to document broadband Internet access performance recently, an interesting exercise.
When I moved into this house about five years ago, we enjoyed an excellent broadband service delivered on an ADSL1 link of about 800m to the RIM/DSLAM. The downstream rate was capped at 8Mb/s and most of the time, most of that speed was available to the end user.
For years I have run a test file transfer every half hour to document access performance, and when asked about recent performance that was an ideal source. I needed to go back to the previous week as last week started with an outage, the RIM batteries seem to have gone flat and Telstra had not been proactive in responding to the condition that left it running on batteries. Continue reading When governments tinker in telecommunications carriage…
A short test drive was conducted to evaluation APRS effectiveness in capturing a motor vehicle journey of about 10km.
This journey is a regular one (the run to the local shops) and due to its familiarity is a good benchmark for performance. Continue reading APRS test drive – 20141114