Technical data

Aeroflex Operation Manual
NAV 2000R SIGNAL GENERATOR - REV. 0 – JULY 26, 2007 - PG 3-36
COMMAND: SET SELECTIVE CALLING GAP TIME
FORMAT: SCL GAP TIME= DDD
This command programs the period of time between PULSE #1 and PULSE #2 in the Selective Calling
mode of operation. The range is from 0 to 999 ms in 1 ms steps.
COMMAND: SET SELECTIVE CALLING TEST FREQUENCY
FORMAT: SCL TEST FREQ= DDDDD.D
This command programs the test frequency used in the Selective Calling mode of operation. This
frequency is output as a test tone following the Selective Calling pulses. The range is from 10.0 to
18000.0 Hz in 0.1 Hz steps.
COMMAND: SET TEST TONE PERCENT OF MODULATION
FORMAT: SCL %MOD= DD[.DD]
This command allows the percent of modulation to be programmed for the test tone in the Selective
Calling mode of operation. The total may range from 0 to 99.00 % and can be specified with 0.01 %
resolution.
3.7 USING THE EXTERNAL AUDIO INPUT
To operate the NAV 2000R in External Modulation Mode, the mode is first selected through the Utility
menu. This is accomplished by pressing and holding any of the mode select keys for more than two
seconds. Then, the EMM mode is selected by pressing number 2 from the numeric keypad. The
external modulation is applied to the RF Modulator Module EXT MOD IN input which is accessible on the
rear of the NAV 2000R.
The external audio input may be used in two ways. The audio applied may be summed with internally
generated audio, or may be controlled separately within the EMM mode. External audio is AC coupled
with a flat frequency response from 10 Hz through 22 kHz. The external audio input may be switched on
or off during the five primary modes by means of the UTILITY MENU or automatically turned on, upon
entering the EMM mode.
During the primary operational modes of the NAV 2000R, the external audio is equally summed with
internally generated audio. With an input level of 1.00 volt peak, the total modulation depth is doubled.
For example, if the total % mod is 40% in LOC mode and a 1.00 volt peak signal is applied to an enabled
external mod audio input, the total modulation depth may be as high as 80%. Adjusting the input audio
level from the 1.00 V peak level will change the ratio of the internal to external audio applied to the RF
modulator.
In the EMM mode, all internal audio generation is switched off. The user may specify the modulation
level produced from a fixed level external source. An audio level indicator tells the user when the proper
level is applied. At this point, the depth of modulation produced matches the specified modulation %.
The NAV 2000R is normally calibrated for an input audio level of 1.00 V peak.
3.8 USING AUDIO OUTPUT
The composite audio signal is accessible at the rear of the NAV 2000R. This signal is capable of driving
a 600 Ω load and is calibrated to provide a fixed 2 V peak signal. Only during the audio control modes,
VORa and LOCa, the output varies, from 0 to 1 V rms, according to the value set within the audio level
field.