Australian Ham Radio Discussion Forum ( AHRDF )

The HF beacon on 28.21150 MHz that was originally destined for installation at Mt Cotton in SE Q'ld is now permanently off-air.

It has been running under the callsign VK4ADC/B from my QTH and on-air for the last 10 months with only a few brief exceptions, with those being for updates to the hardware and software. It was a purpose-built beacon using mainly SMD devices with a single PICAXE controller to set the frequency synthesiser, set the RF power stepping and also the CW ID generation.

The lack of support from SARS (The Southside Amateur Radio Society in Logan) in ensuring a permanent installation on Mt Cotton is the reason behind the shutdown.

Doug VK4ADC

This beacon has been reprogrammed to 28.265 with callsign VK4RRC and will be installed at Wamuran, SEQ, with the other Redcliffe & Districts Radio Club repeaters. The "box" was donated to RDRC and handed over to Kevin VK4UH on the 26th Feb 2017 and is only awaiting the installation of a suitable 28MHz base antenna on-site before it is likely to be operational.

It is set to do the basic CW ID (VK4RRC) at about 7 watts RF out, then RF power step down from 5 watts to 10mW at 1 second intervals. This timing cycle repeats every 20 seconds and a full length ID (VK4RRC Brisbane QG62JX81) every sixth ID. Good luck hearing the 10mW power level unless you are very close to it !!

The beacon will do an RF power re-calibration at least every hour and that revalidates any account antenna impedance changes, power supply voltage changes or component ageing to maintain correct RF output values. This part of the program cycle is obvious as it has "bursts" of increasing RF signal level as it re-sets to meet the targets (instead of decreasing as the power levels step down in the normal beacon cycle - as above in para 2).

It will also add either a HV or LV to the CW ID to indicate either high or low power supply voltages beyond normal tolerance. The unit will cease to produce normal RF output if the supply voltage drops below 11V or exceeds 15V to ensure that RF emissions & transmitter stability is maintained - a LED on the front panel flashes to indicate this state but only about 10mW(/nothing !) is transmitted.

Hopefully it will provide a useful beacon facility to many - for many years.

73 Doug VK4ADC