Yaesu FT DX 9000 CONTEST - 2, Руководство по эксплуатации

Страница: 78 / 168

Page 76 FT
DX
9000 C
ONTEST
O
PERATION
M
ANUAL
SSB/AM M
ODE
T
RANSMISSION (L
OW
- D
ISTORTION
CLASS-A O
PERATION
)
L
OW
- D
ISTORTION
CLASS-A O
PERATION
Class-A operation of the FT
DX
9000 Contest transmitter is provided, yielding ultra-low distortion products during SSB
operation. Power output during Class-A operation is 75 Watts.
To engage Class-A operation,
press the CLASS-A switch
(#
). The imbedded Red LED
will light up, confirming that Class-
A operation has been selected.
Engaging the “Class-A” mode
actually places the transceiver in
a condition whereby the Bias
level may be adjusted, using the
BIAS control (# ), to set the
transceiver for operation anywhere between Class A and Class
AB (which has lower heat dissipation but higher distortion
products). Clockwise rotation of the BIAS control in-
creases the Bias, and fully clockwise rotation of the BIAS
control will place the transmitter in fully Class-A opera-
tion. Counter-clockwise rotation of the BIAS control
will move the transmitter toward Class AB operation.
Advice
During Class-A operation, ten Amps of Bias current will be flowing, regardless of the modu-
lation level that leads to actual power output. Therefore, if the ambient temperature in your
operation location is high, the transceiver temperature may rise as well, due to the high bias
level (which must be dissipated as heat). Depending on the temperature, you may wish to
reduce the setting of the BIAS control, so as to reduce the amount of heat being generated.
During Class A operation, we recommend that you monitor the heat sink temperature by pressing the TEMP switch
(#
) so as to engage the temperature monitoring mode of the TEMP/SWR meter (# ). Usually, the temperature
will be well below the 80 °C “Red Zone,” because the fan speed will increase to control a rise in temperature. If you are
operating in a hot environment, though, and the increasing fan speed does not maintain the temperature below 80 °C,
try adjusting the Bias Level temporarily in the direction of Class AB operation; this will reduce the amount of heat
being dissipated in the heat sink.
The Bias Level is displayed on the VDD/BIAS meter (#
) when the BIAS switch (# ) is pushed. On the “Bias”
scale, “0%” represents Class AB operation, while “100%” represents Class A operation.
An innovative aspect of the “Class-A” mode is that the actual power output is always limited to 75 Watts. So even
though you might adjust the BIAS control in the direction of Class-AB operation, the power output will not rise; this
eliminates the need, for example, to re-tune your linear amplifier, if used.
Quick Point
BIAS knob
CLASS-A switch
Class-AB and Class-A Operating Principle
Input
Class-A Class-AB
Continuous adjustment of the
Bias Level between Class-A
and Class-AB is possible.
To exit from the CLASS-A mode, press the CLASS-A
switch once more. The Red LED imbedded in the switch
will go out, confirming that the CLASS-A mode has been
disengaged.