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• AUDIO FILTERS
Table 3-4 lists audio filter characteristics.
Highpass:
5 Hz
5 Hz
300 Hz
3 KHz
Lowpass:
20 KHz
20 KHz
3 KHz
300 Hz
Filter
Char-
acter-
istic
Filter
Frequency
Mode
(Not More
Than 0.5 dB)
Frequency
(Not More
Than 3 dB)
300 Hz
3
KHz
3 KHz
300 Hz
Frequency
(At Least
20
dB)
170
Hz
1.7
KHz
40
KHz
5.4 KHz
540
Hz
• MODULATION
In the frequency MODULATION DISPLAY (figure
3-16), view the composite modulation audio waveform
in generate mode or the
demodulated
audio in monitor
mode. Analyze waveforms on the scope to measure
deviation graphically. Use the MONITOR BW switch to
select wide or narrow bandwidth. In the wide position,
adjust frequency modulation level from
a
to 75 KHz
peak deviation. In the narrow position, adjust the range
from
a
to 20 KHz. The display's vertical deflection is
calibrated for FM, generate and monitor modes, in
three ranges with 0.25 KHz, 2.5 KHz, and 25 KHz per
graticule division. Use the OSCILLOSCOPE modula-
tion controls shown in figure 3-41 to select deviation
level, vertical and horizontal. To set the range, adjust
the Vert control to the proper KHz/Div.
The
modulating signal is generated internally by the
MODULATION SECTION. Refer to paragraph 3.3 in
this manual.
TABLE 3-4.
AUDIO FILTER CHARACTERISTICS
CENTERFREQ
07) 156.2800
MHz
• AM DEMODULATION
The monitor demodulates AM to a 100070 modulation
level. The frequency response is the same as for FM ex-
cept that the lowest allowable high pass filter cutoff is
300 Hz.
• SINGLE SIDEBAND DEMODULATION
The monitor has a minimum dynamic range
of
30
dB in
the sideband mode. The frequency response is the same
as for FM.
dB
KHz
• AUDIO MONITOR
A speaker monitors the recovered signal in the monitor
mode and the modulating signal in the generate mode.
The speaker drive signal is also applied to the receive
audio pin of the microphone/headset connector. Use
special function control to disable the speaker while
maintaining the headset audio signal with volume con-
trol. The audio signal frequency response ranges from
300 Hz to 20 KHz in the wide band and from 300 Hz to
3 KHz in the narrow band.
FIGURE 3-16.
MODULATION DISPLAY
3-9
FIGURE 3-17.
SPECTRUM ANALYZER DISPLAY
• SPECTRUM ANALYZER
The Spectrum Analyzer display, figure 3-17, shows
center frequency, channel number, and operating fre-
quency. Use the keypad to enter the channel number,
from 01 to 32 or enter a center frequency directly. Use
the Spectrum Analyzer to identify interference, trace RF
and IF signals, measure transmitter harmonics, check
spurious response and receiver local oscillator radiation.
The CRT displays the appropriate frequency from the
RF Memory table and changes the system operating fre-
quency as required. Entering a new frequency changes
the channel number to a dash and changes the system
operating frequency as required. The CRT displays a
window of the RF spectrum at either the antenna or
transceiver port in a range selected from 1 MHz to 1,000
MHz programmable in 100 Hz increments. The ob-
served window for the Analyzer can be controlled with
the Dispr/Sweep and RF Scan controls. The Spectrum
Analyzer has a dynamic range of at least
75
dB with the
Step attenuator in the 0 dB position. With the at-
tenuator, the usable range
can be
extended
up
to
the
maximum allowable input levels. When using the at-
tenuator, add 10 dB per step attenuation to the actual
dB reading on the scope. The usable sensitivity is at least
-95 dBm at the antenna port and -65 dBm at the
transceiver port.
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