14
8
DX-1d
DESCRIPTION
8.1
RF Section
The RF section occupies the right hand side of the DX-1d (looking from the top - front). See picture in 1.1.
RF Switch and tuned circuits
At the front of the amplifier are two variable capacitors, for plate and load tuning. A 9-position ceramic
switch is employed for the 9 operating bands. Next to the switch is the 40 to 160 metre tank coil. The silver
plated, large diameter copper tube is the 10 to 30 metre tank coil.
RF Sub-chassis
The 4CX800A tube is positioned on a separate RF sub-chassis. All the connections to the tube, except for the
plate, are under this sub-chassis. A 9-way heavy duty connector is used for the outside connections. The fan
blows air into this sub-chassis, which is forced out through the ventilation fins of the tube. The air
temperature is sensed by a sensor placed above the tube. The sensor must stay in a position close to
horizontal. Make sure you are not pushing it down, too close to the tube, as high voltage exists between them.
The plate is connected to the RF network and to the choke supplying the 2100VDC voltage to the plate of the
4CX800A tube.
8.2 Mains transformer
The transformer is the heart of the amplifier, a high performance type, designed to reduce the size and weight.
It is built with a generous reserve of power, handling easily the DX-1d requirements in continuous operation.
The primary can be wired for 120V, 200VAC, 220VAC, 230VAC or 240VAC operation.
See Figure
2. There
are several secondary windings, as follows:
•
Filament supply
•
Low voltage supply to the controller board
•
QSK module supply
•
Bias supply
•
Screen grid supply
•
High voltage supply
8.3
H. V. Power Supply
A full wave bridge rectifier and filter converts the high voltage AC into high voltage DC with a huge reserve
capacity of 58 microfarads.
8.4
Soft start module
At power up, the mains power is gradually applied to the transformer by the soft start module. The power is
gradually applied over a time of about 5 seconds, avoiding the high inrush current typical for such big loads.
8.5
Sensor module
A small metal box positioned at the output of the DX-1d. It detects the forward and reverse power, for
measurement and display.
8.6
Antenna relay / QSK module
In the standard DX-1d, the antenna relay is controlled by the transceiver, via the control board. It switches the
antenna between the transceiver, during reception, and amplifier, during transmission. It is also used to bypass
