15
For prolonged transmissions the amplifier gain can drop between 5% and 10% during the first minute
which is normal while temperature balance of the tube is achieved. You can easily compensate this by
increasing the drive power slightly. Once the drive power has been set, the output power remains
stable with the time for hours.
C A U T I O N
For transmissions longer than 15 minutes the external auxiliary fan must be
installed (see S.2-5).
4-6. ON LINE Information Screens and Control Functions
a) Besides the Warming Up and TRI (described above in S.4-1 and S.4-4), you have 12 more
Information screens available. They are as follows: Forward Power, Reflected Power, Output Power
(difference between forward and reflected), Antenna VSWR, Drive RF Power, RF Power Gain, Plate
Current, High Voltage, Plate RF Peak, Screen Current, DC Power Input (product of plate current and
high voltage), and Exhaust Air Temperature (Celsius and Fahrenheit scales). You can use them to
monitor the technical state of the amplifier and associated parameters, in a digital form.
Selection is made by the PREV and NEXT buttons. You may change them while the amplifier is used
and controlled in operate and standby modes, changes transmit and receive, without any influence by
the measurement process.
b) You can control the display brightness, Auto-Operate feature, and antenna output assignments
while ON LINE. In order to enter the control menu, press the PREV+NEXT buttons simultaneously
and hold them for two seconds. Further proceed as described for OFF LINE mode below - see S.5-1,
S.5-2, and S.5-3 for details.
4-7. Auto-Protection System
When any abnormal condition is detected, the amplifier will evaluate the risk and may use three
different degrees of protection, depending on the nature of the problem. Each event is accompanied
by descriptive text. The VFD brightness is flashed to attract the operator's attention.
a) The first degree of protection consists of a warning message only and does not interrupt
transmission. Examples include "Reduce Drive", "Plate Current", etc. You may continue to transmit
under such conditions but you are close to a trip threshold.
b) The second degree of protection is a trip to standby mode (Soft Fault). An example is ** GRID
CURRENT **. All Soft-Fault messages are marked with two asterisks on both screen edges. The
message remains on the display until any button is pressed or until the auto-operate function returns to
“operate mode” automatically. The Soft Faults permit correction by the user, such as by using less
drive, improving antenna VSWR, etc.
c) The third degree of protection is a trip to OFF LINE mode (Auto-Protection). See S.6-5 -
Troubleshooting. If it is not evident why the trip has occurred, you may try to turn the amplifier on
again. If the problem persists, you will need to contact your dealer - see S.1-2.
N O T E
The 6dB input attenuator is automatically inserted about one second after faulty
tuning is detected at drive levels above 20W. It is also switched off at every PTT
release (unless inserted manually).
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