aprx is APRS iGate / digipeater server software for the *nix environment by Matti Aarnio. In my case, I am developing and running on RPi / Rasbpian Wheezy.
This article comprises notes on the digipeater module as modified over recent weeks to address shortcomings in its operation. Continue reading Notes on my fork of aprx
A short test drive was conducted to evaluation APRS effectiveness in capturing a motor vehicle journey of about 30km.
The test area is between two digipeaters spaced almost 40m apart, so within the overlapping coverage area of VK2RHR-1 about 17km NW of the test area, and VK2AMW-1 about 17km SW of the test area.
Three position capture devices were used:
Fibre rope has applications in antenna rigging, typically for halyards and tails to support the ends of wire antennas such as dipoles. The use of fibre rope for guying applications has issues due to shrinkage when wet.
Much is made of the ‘best’ fibre rope for these applications, and the almost universal answer is black Dacron (Polyester) in small sizes from 2.5mmm to 6mm diameter. The smaller sizes are usually a braided construction, commonly known as venetian cord. Claims are that the Polyester rope is strong, UV proof and rot proof. Whilst Polyester rope is resistant to mild acids and alkalis, it is damaged by strong alkalis (such as might develop when an alkaline solution dries on the rope). Continue reading Synthetic fibre rope for antenna rigging
In earlier articles I documented a trial of aprx v2.08r593:
Encouraged by Kenneth Finnegan who merged some fixes by WB4XO (which still didn’t work properly), I set about resolving some problems.
Further fixes and some enhancements have been pushed to the source fork at . This was forked from PhirePhly/aprx which in time may pull the changes.
You can browse for brief descriptions of the changes.
Recent Debian packages for RPi based on my fork have been uploaded to https://owenduffy.net/files/aprx/ .
A reader of my article End fed wires – new hams love ‘em asked about the performance of the matching transformer described at (Osborne 2014).
(Osborne 2014) gives the transformer design above using a FT82-43 ferrite toroid with three turns on the primary. The concept is to adjust the antenna length and C1 for a ‘perfect match’. Continue reading End fed wires – another matching case study
Garmin GPS35 is a GPS pod with serial connection carrying NMEA data.
They are supplied with a range of connectors, and for use with APRS systems, one may want to replace the connector with the common DE-9 wiring for trackers. Continue reading Garmin GPS35 DE-9 (F) wiring
In earlier articles I documented a trial of aprx v2.08r593:
Encouraged by Kenneth Finnegan who merged some fixes by WB4XO (which still didn’t work properly), I set about resolving some problems.
Above is the RPi sitting on a TNC-X KISS TNC connected to the TNC’s USB port. In this case, aprx uses the supplied KISS interface, it does not use Linux kernel support for AX.25. Continue reading Headless aprx APRS server
New hams are often advised quite poorly, justified by the mantra that “any antenna is better than no antenna at all”. The more confident the advisor, the more jargon, the more unsupported, the more the advice is soaked up by eager newbies. Not just soaked up, but learned so the newbie can talk like the pro… even if they also do not understand the subject matter. Spruiking BS has always been a feature of ham radio.
Recent online discussion illustrated and recommended a 40m dipole strung on a timer fence at a height of about 1.5m to a new ham with a 10W power limit in search of good solutions from ‘experts’. Continue reading Effect of ground on HF horizontal dipole efficiency
This article documents a line-up procedure for the MFJ-1270B TNC. This is an advanced procedure, you should not tackle it without appropriate knowledge and experience. Continue reading MFJ-1270B TNC alignment
Many years ago I bought a Tigertronics Signalink USB, principally for measurements using FSM and NFM.
A nuisance with the device is the lack of a simple means of disabling PTT. This is particularly important if the system is being used for noise figure measurement with an expensive calibrated noise source which will not withstand transmitter output.
This note describes the fitting of a front panel PTT disable switch. Continue reading Signalink USB PTT disable