Operating instructions

RF Technology PA501 Page 5
1 OPERATING INSTRUCTIONS 1.2 Front Panel Indictaors
1.2 Front Panel Indicators
PWR LED The power (PWR) LED shows that the dc supply is connected to the
transmitter.
RFO LED The RF output (RFO) LED indicates that the amplifier is being driven
and that the forward output power is above a preset level. This preset indication
level is generally set 1 - 3 dB below the preset output power level.
TEMP LED The temperature (TEMP) LED indicates (illuminates) should the
amplifier's internal temperature become too high. The RF power is
automatically reduced by 6-10 dB if the internal temperature rises above safe
limits and the cooling fans run continuously until the temperature drops.
1.3 Internal Adjustments (Rev 05/9151)
All internal adjustments are factory set and should not need to be changed under normal
conditions. A possible exception to this is the RF output power level which may need
to be changed to comply with local licensing requirements. The low forward power
warning circuit should be set at the same time as the forward power level. The controls
are described below, and the recommended procedure for carrying out the alignment is
set out in section 3.1.
WARNING
Ensure that the power setting complies with the
requirements of your licensing authority. Failure to do
so may result in penalties being imposed by the
licensing authority.
Output Power The output power is set by VR136. This is nominally set to 100
Watts (+50dBm), but may be set to any value between 40 and 125 Watts
depending upon local regulations in the destination country, and the model of
power amplifier. VR136 determines the threshold affecting the ALC voltage that
is fed back to the transmitter module to regulate RF output power.
RF Level Detector The forward RF power threshold associated with the RFO LED on
the amplifier front panel is set by VR143. This is nominally set at half to three-
quarters of the preset output power, 50 - 90 Watts.