Low- Distortion Class-A Operation - Yaesu FTDX9000D - DATA MANAGEMENT Operation Manual

SSB/AM M T
ODE
L
Class-A operation of the FT
tion. 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 trans-
ceiver in a condition whereby the Bias level may be ad-
justed, 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 increases the
Bias, and fully clockwise rotation of the [ BIAS ] control
will place the transmitter in fully Class-A operation.
Counter-clockwise rotation of the [ BIAS ] control will
move the transmitter toward Class AB operation.
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.
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RANSMISSION OW
- D CLASS-A O
OW ISTORTION
9000D transmitter is provided, yielding ultra-low distortion products during SSB opera-
DX
[ BIAS ] knob
- D CLASS-A O
ISTORTION
PERATION
[ CLASS-A ] switch
A A A A A
During Class-A operation, ten Amps of Bias
current will be flowing, regardless of the
modulation level that leads to actual power
output. Therefore, if the ambient temperature
in your operation location is high, the trans-
ceiver 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.
Because you can monitor the heat sink tem-
perature on the TFT, you can always be aware
of a rise in temperature during Class-A opera-
tion. Normally, the temperature is below 80°C;
if it rises to near or above this value, however,
we recommend you adjust the [ BIAS ] control
toward Class AB (more to the left) so as to re-
duce the heat being dissipated.
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.
FT 9000D O
DX
PERATION
D D D D D VICE VICE VICE VICE VICE
M
PERATION ANUAL
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