South Coast Repeater and Beacon Group

G8BKE/P - 47GHz beacon

47GHz Beacon - Designed and Built by John - G8ACE.

During the winter of 2001/2002 some propagation tests were done between the QTH of G8ACE and G3JHM. A beacon transmitter was constructed and operated for six months until April 2001. After that date the transmitter remained unused. During the Autumn of 2003 the beacon was rebuilt with new oscillator (OCXO) and phase lock loop (PLL) modules. This employs the CT1DMK PLL design approach using a CPLD. A high degree of oscillator stability is achieved using a 5 MHz reference oscillator to lock the transmitter oscillator. The block diagram for the beacon transmitter is shown below.

October 2012, G8KQW and G8ACE Received this beacon while operating from Cheesfoot Head, Hants at a distance of 75km. This Video shows the good signals thay got

The low power available from the final gaasfet multiplier means that a high gain antenna is required to produce a reasonable ERP. A 20db horn antenna achieves this but at the expense of directional coverage. By suitable bearing and location the beacon can cover an area of higher population although reception will be limited to line or almost line of sight (LOS) paths due the nature of millimetric wave propagation.

Some pictures of the beacon and the installation

This picture shows the prototype beacon board, The 5MHz ovened oscillator can be clearly seen in the bottom right.

The mast has been tilted over to allow the 47GHz beacon to be attached to the upper part of the head unit. The beacon is positioned such that the RF is directed through local trees.

Andy G4JNT and Chris G8BKE finalise work on the beacon before the mast is wound back up.