4-1.1 Basic FM Transmitter Testing Setup
Refer to figure 4-1. Connect the analyzer's RF
I/O port to the RF output of the transmitter under
test. Connect the analyzer's MOD OUT jack to
the mic audio input of the transmitter under test.
CAUTION
For transmit power output measurements,
connect the transmitter under test only to the
analyzer's RF I/O port. Do not connect it to
the ANT port. The ANT port is used with an
antenna for "off-air-" reception.
The built-in RF load dissipates up to 50 W for
three minutes and up to 125 W for one minute.
If a high-power transmitter is keyed into the
analyzer for a time long enough to threaten
overheating the power measuring circuitry,
the system's audible alarm sounds and the
display changes to the RF LOAD
OVERTEMPERATURE warning, signaling
the operator to unkey (refer to
paragraph 3-4).
4-1.2 Transmit Power, Frequency, and
Frequency Deviation Measurements
1. With the cursor located within the RF
Control zone (refer to paragraph 3-2), press
the
MON softkey to place the analyzer into
its Monitor mode of operation.
MON GEN
DUPLEX
Monitor Mode
Softkey
2. Within the RF Control zone, set as follows:
RF Control:
Preset: - - B/W: NB
MONITOR
Freq:
Attenuation:
-20 dB
816.5000 MHz
Mon RF In: RF I/O
Modulation Type:
FM
Transmitter Carrier
Frequency
3. Set the SQUELCH control to threshold. For
low-power transmitters, may be necessary
to use a lower attenuation value in order to
unsquelch the monitor (refer to paragraph
3-5.1). Too high of an attenuation setting or
too tight a squelch setting inhibits the
frequency error reading (refer to paragraph
3-7.1.1). Accurate measurements require
sufficient signal level from the radio to fully
quiet the analyzer's receiver. Use good
quality cable of minimum length to prevent
cable-loss which can be a significant factor
in RF power measurements, especially at
UHF and above.
65
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