70 MHz page
Call: OZ1BXM QTH: Holstebro JO46GI
Status per 10-July-2006
The OZ-transverter and the PA have been sold to another ham operator. The
reason for this is lack of activity in my area.
Status per 02-Oct-2005
The OZ-transverter and the PA are fully assembled. The RX part is working,
but the TX part needs alignment. A dipole antenna has been mounted on the
roof and I've started listening for 4-meter beacons.
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 OZ1BXM.
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.
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.
25 W PA for 70 MHz
Modified 10-July-2006 by Lars Petersen, OZ1BXM.