Operating instructions

LOCAL OPERATION
3-27
Making measurements
This section describes the actions needed to make measurements of each parameter associated
with transmitter testing. All tests are described individually as ‘one off’ tests, but in practice, once
set up, all active parameters will be measured simultaneously with continuous updating and the
results displayed using the selected measurement units.
The results obtained from tests can be stored for later analysis or transfer to hard copy by making
use of the internal setup/results memories or the optional memory card facility. Test mode screen
settings can similarly be stored for future use. All of these features are described under Stores,
Settings/results, or Printer, later in the chapter.
Transmitter power
Broad Band and Narrow Band power measurements
The monitor has both Broad Band and Narrow Band power measurement facilities. The Broad
Band power meter measures the total average power of all signals present at either RF input, while
the Narrow Band power meter measures only the average power of the signal contained within the
IF pass band selected for the Tx TEST mode.
The facilities of the Service Monitor allow the RF signal generator to remain active in the Tx
TEST mode. Therefore the signal from this will be present at common points within the RF
input/output circuits of the Service Monitor and will contribute to measurements made by the
power meters. When making measurements where this will make any significant difference to the
measurement, disable the RF generator by selecting the
RF Gen OFF condition from the Rx TEST
mode or the Dx TEST mode.
Narrow band power measurements cannot be made when the frequency of a transmitter has been
set using the [Auto Tune] key.
The maximum continuous power rating of the ‘N-Type’ connector is 50 W with a minimum
indication of 5 mW. Lower levels of input signal are indicated as voltage levels, the first bar chart
graduation being at 20 µV. The maximum continuous power rating of the antenna BNC connector
is 5 W.
A power overload condition is indicated by an audible and visual warning. Should this
condition be indicated, immediately reduce the level of RF power from the transmitter into
the Service Monitor.
Do not stop the warning by switching off the Service Monitor, as this will silence the
warning but will leave the excessive RF power connected to the internal load.
Do not attempt to stop the warning by disconnecting the RF connector, as this can damage
the transmitter and may cause electric shock or skin burns
WARNING
Hot surfaces
Take care when touching the RF Input Type N connector after the application of
high levels of continuous power. If 50 W is applied for a prolonged period, the
temperature of the connector can become excessive.
With the monitor in the Tx TEST mode, and the transmitter connected to the monitor as described
above, key up the transmitter.
The RF power bar chart gives an analogue representation of the active power meter reading. A
digital read-out of the power is displayed above the bar chart.
The options available for the digital read-out from the power meter are dBm, Watts or Volts.
The bar chart can be auto-ranging or manually selected. See
Bar charts on page 3-15.
External attenuators can be included in the input path to the Service Monitor. The value of any
such attenuators can be entered into Setup Page 1 of the Service Monitor, which will cause the
power measurement software to calculate the power at the attenuator input. The result of this
calculation is shown on the RF power bar chart and as the digital power reading.
Power readings which include an attenuation factor have an inverse video 'A' adjacent to them.