Freedom R8100 SERIES, Operator'S Manual

Page: 233 / 255

233
4.1.2 Transmit Power, Frequency, and Frequency Deviation Measurements
Place the R8100 in Monitor mode by pressing the Monitor front panel hard key. Press the RF Zone soft
key and set the Monitor Frequency to that of the radio under test and the Modulation Type to FM. For
best accuracy set the Bandwidth just wide enough to cover the channel spacing allocated to the radio under
test.
To eliminate the background noise from the R8100 when the transmitter isn’t keyed, adjust the squelch
control appropriately. With the volume control set to a comfortable listening level turn the threshold
control clockwise to just quiet the R8100 receiver. (See Front Panel Control Knobs.) For low-power
transmitters it may be necessary to reduce the RF attenuation value to un-squelch the monitor when the
transmitter is keyed. Too high an attenuation setting or too tight a squelch setting also inhibits the
frequency error reading. Deviation and frequency error measurements require sufficient signal level from
the radio to fully quiet the analyzer's receiver. Accuracy is best when the signal levels are 10 dB or higher
than that required to quiet the 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.
Key the transmitter and read the power (“Input Lvl”), frequency error (“Freq Error”) and deviation
(“Deviation”) in the RF Zone section of the R8100 main screen. Refer to your radio's service manual to
determine if power, frequency, and deviation are within specified limits and determine if any adjustments
are required.
4.1.3 Modulation Measurements
Place the R8100 in Monitor mode by pressing the Monitor front panel hard key. Press the RF Zone soft
key and set the Monitor Frequency and Modulation Type to match that of the radio under test. For best
accuracy set the Bandwidth just wide enough to cover the channel spacing allocated to the radio under
test.
CTCSS (Continuous Tone-Coded Squelch System) test
Enable the CTCSS mode on the radio (called PL or DPL on Motorola units). Enable the 300 Hz low pass
filter on the R8100 to prevent external pickup in the microphone from causing deviation errors. Key the
transmitter and read the deviation of the PL/DPL tone. Refer to the radio’s service manual to determine
if an adjustment is required.
Voice frequency modulation and quality test
In the R8100 Audio Zone set the High Pass Filter to 300 Hz and the Low Pass Filter to 3 kHz. Set the
Fixed 1 kHz Mode to continuous. Set the Fixed 1 kHz level at the R8100 Mod In/Out connector to the
minimum required for proper microphone sensitivity as specified in the radio service manual.
Note: The
voltage levels displayed in the Audio Zone are peak open circuit voltages. Verify proper microphone
sensitivity by reading the deviation and comparing to the service manual specification to determine if
adjustments are needed.
Set the Fixed 1 kHz level at the R8100 Mod In/Out connector to the maximum required for proper
microphone sensitivity as specified in the radio service manual. Navigate to the R8100 Meter Zone and
select the Internal Distortion meter. Read the percent distortion and compare to the service manual
specification to determine if adjustments are needed.