APRS has had problems since its inception, and it is not surprising… but the future of APRS has arrived. Continue reading The future of APRS is here…
Month: September 2014
A simple preamp for dynamic capsules to suit radios using electret microphones
A lot of radios are made today to use an electret microphone which has a higher output than common dynamic capsules and may require a preamp to comfortably obtain sufficient audio.
This article describes a microphone + preamp intended as a drop in replacement for an electret capsule.
An electret capsule contains an integral FET preamplifier, and the common two terminal version of the capsule depends on an external load resistor (commonly around 4.7kΩ and source of supply current (commonly from 6-12V via the load resistor.
Above is the preamp schematic from an LTSpice model. A common emitter amplifier operating in this circuit has re of about 20Ω, and so voltage gain from collector to base is very high at 3000/20=150 (assuming total collector load of 3kΩ). Continue reading A simple preamp for dynamic capsules to suit radios using electret microphones
Roger Beep fitted to MFJ-1263 microphone / rig switch
Some years ago I purchased a used MFJ-1263 microphone / rig switch with a view to using it as an ongoing test bed for my Roger Beep module.
The Roger Beep module was assembled with 6 way 90° single row header pins for easy connection and disconnection.
The module was built, tested and adjusted for audio output level and encapsulated in clear heat shrink. The cable was made from parts from ready made 3 way RC servo jumpers with the wires removed and inserted into more suited back shells. Continue reading Roger Beep fitted to MFJ-1263 microphone / rig switch
End fed wires – new hams love ’em
Hams impoverished for space to erect a ‘full size’ antenna for HF pursue a range of options and end fed wires figure highly.
New hams who heard the maxim that ‘any antenna is better than no antenna at all’ will try to use bed frames, window frames, balcony railings, anything metallic to get on air. This cry for mediocrity is to prevail over a quest for understanding, ham radio as it has evolved.
The ‘net abounds with conflicting advice:
- (Yates 2010) recommends a T50-2 powdered iron core;
- (VK2AVR 2014) states
do not use a powdered iron toroid.. they won’t work.
They cannot both be correct. Continue reading End fed wires – new hams love ’em
Towards a reliable APRS iGate – #2
Towards a reliable APRS iGate discussed efforts to implement a robust and reliable APRS iGate / digi. The article ended by mentioning further work on initialisation scripts. Continue reading Towards a reliable APRS iGate – #2
The sign of reactance
There is little doubt that overall, hams have dumbed down as technology has raced ahead.
An interesting result of this is the appearance of new antenna analysers aimed at the dumb ham.
What is the dumb ham in this context? Continue reading The sign of reactance
TNC-X – channel access behaviour
I have been investigating ‘lost APRS packets’, a result of many root causes.
One is a perception that when I drive in the local area, I often do not hear my own digi ‘echo’ yet I find that it did receive a packet and submit it to APRS-IS. This problem is much more apparent using a TNC-X that with any other KISS TNC in its place. Continue reading TNC-X – channel access behaviour
Does anyone assess to their digi / iGate performance?
During recent evaluation of a range of APRS servers and TNCs, I have inspected APRS-IS records and my own server logs to identify possible anomalies caused by the equipment under test.
In that time I have found defective records caused by digi / iGates: VK2JMA-5, Vk2YGV-5, VKWUWP-2, VK2UWP-1, VK2MPJ-1,VK2ZEN-5, VK2AMW-1, VK2RHR-1, VK2LKH-1, VK2MB-1, VK2BEN-1. Continue reading Does anyone assess to their digi / iGate performance?
Towards a reliable APRS iGate
An APRS iGate necessitates some form of computer in the centre of the configuration.
Over recent weeks, I have evaluated a number of configurations for VHF based on Windows and Linux (RPi) to assess their reliability, though it is doubtful that a configuration to rival UIDIGI reliability and availability is likely. Continue reading Towards a reliable APRS iGate
Ubuntu LTS upgrades get better – v14.04
On 01/09/14 I commenced upgrade of Ubuntu 12.04 LTS “precise” to Ubuntu 14.04 LTS “trusty”. (LTS is for “Long TIme Support” and it is supposed to be the reliable stream rather than experimental.) Continue reading Ubuntu LTS upgrades get better – v14.04