VK6RBU Bunbury, Western Australia

The Indian Ocean Propagation Project

From 18th April, 1996 a new 50 and 144 MHz beacon service commenced continuous operation from a location near Bunbury, Western Australia. (Locator OF76). The transmitters have been established on 50.306 and 144.560 MHz with the particular long term aim of providing a useful signal level for the investigation of both ionospheric and tropospheric propagation to the West towards Africa across the Indian Ocean. Contacts to Africa from Australia have already been made on 50 Mhz during the last Solar Cycle, but the Indian Ocean has yet to be bridged via tropospheric media.  The prospect of sustaining a signal by tropospheric media from Western Australia towards Africa has been predicted by meteorologists and others as long ago as the 1960's. Already amateur operators on Reunion Island in the Indian Ocean are cooperating with this project, with signals reported on two occasions from the 144.560 Mhz transmission. The effective radiated power on a bearing of 260 degrees is approximately 100W, horizontally polarized.   About 10W erp is radiated on the reciprocal bearing of 080 degrees True. The antennas are 3 and 4 element yagis respectively, mounted at about 25m above ground. The site is about 300m above sea level, with the Indian Ocean as horizon at about 20Km distant. The "rear" lobe should provide a useful signal towards the Eastern States of Australia. The keying mode is on-off on 50.306 and FSK on 144.560. The latter is key down on 144.560 MHz, with key up 800 Hz lower. The keying cycle is somewhat different to normal.  It is VK6RBU -long dash-, followed by 10 seconds of 5mS pulses spaced 100mS.  The purpose is to provide the basis for individuals to experiment with looking for backscatter echoes from reflecting media, by displaying the signal on a CRO. The same keyer is used on 50 and 144, so the 144 signal might be used to trigger the display  of 50 MHz echoes, and so determine the distance away that these are occurring.

An Additional Beacon

A second 144 Mhz beacon transmitter is near completion,
which will be made available to operators
on Reunion Island for installation.

Full details of this will be made available as this part of the project proceeds.

Any reports of these transmitters to VK6HK:

* QTHR

* Via e-mail - [email protected]

* Via phone/fax +61 08 9446 2864

Installation of VK6RBU

Cec Andrews VK6AO

Wally Howse VK6KZ