70 MHz transverter

Status per 10-July-2006

Status per 02-Oct-2005

Station description

Antenna

My 70 MHz antenna is a horizontal dipole. The antenna is made of two aluminium rods each 104 cm long. The rods are strapped to a wood dowel which provides the mechanical strength of the assembly. I have painted the dowel grey to protect it against the weather. Additionally, the grey colour makes is appear "aluminimum look". The antenna cost me 100 DKK (15 EUR) and some hours of labour. It is connected to the transverter using 20 m Aircell 7 coax cable.


Upper antenna: 70 MHz dipole;
Lower antenna: Vargarda 3EL2 yagi for the 2 meter band.


Center of the 70 MHz dipole.


The 70 MHz dipole is slightly taller than me (OZ1BXM).

OZ-Transverter

I have assembled a 70 MHz transverter kit. The unofficial name of this kit is OZ-Transverter. The kit is designed by OZ2M Bo Hansen and OZ7IS Ivan Stauning, and described by OZ2M on his homepage. A 25 W multi-mode PA has also been developed by OZ2M.


The finished OZ-transverter.

The upper row of components form the RX chain, the center row the LO, while the lower row components compile the TX chain. The PCB is built into a sheet-metal box. Three BNC sockets are fitted for RF-signals: 28 MHz input/output at the left; 70 MHz input at the upper right; and 70 MHz output at the lower right. Feed-through capacitors are fitted (left box wall) and they decouple the supply voltage input, the PTT voltage input, and the antenna relay voltage output.


Adjusting the Local Oscillator.

The snapshot above shows my working table on a Monday evening while adjusting the local oscillator. The Thandar counter displays the frequency of the 42 MHz LO.

PA

25 W PA for 70 MHz
The picture shows the almost finished PA. The Mitsubishi power module is mounted on a large heat sink. Two pieces of copper foil connect the ground plane of the power module to the PCB ground plane. The PCB contains a bias circuit, a low pass filter and a power meter circuit. A sheet-metal box covering all components was fitted after the photo was taken.