Aeroflex 2946A Instructions d'exploitation télécharger pdf (Page 63)

LOCAL OPERATION

3-24 46882-311D

More (de-emphasis, FM deviation pk/rms, modulation dBr)

Press the [More] key. The right hand soft keys change, to allow selection of de-emphasis mode,

and FM deviation and modulation measurement modes.

De-emph

De-emphasis filtering, ON/OFF, is toggled by alternate presses of the [Deemph] key. The

de-emphasis filtering uses a 750 µs time constant to give a 6 dB/octave roll-off.

De-emph ON appears on the main display when appropriate. No indication is given to show that

de-emphasis is not on.

Press [More] to return to the previous menu or [Return] to display the main Tx TEST menu.

FM Dev Pk/rms

Toggles between measuring FM modulation with RMS or with peak detectors. The measurement

mode –

Pk or rms – appears to the left of the FM deviation bar chart.

Press [More] to return to the previous menu or [Return] to display the main Tx TEST menu.

Mod dBr

Toggles between measuring the absolute AM or FM modulation or the AM or FM modulation

relative to the value registered at the moment the key is pressed. The modulation level is shown

in units of dBr when appropriate.

Press [More] to return to the previous menu or [Return] to display the main Tx TEST menu.

Audio generator setup

Freq. range 10 Hz to 20 kHz

Level range 0.1 mV to 4 V rms

Shape option Sine or square

To set up the audio generators in order to modulate the transmitter, press the [Audio Gen] key.

This will display the audio setup menu shown in fold out diagram (2 -4).

Set up the audio generator(s) for the required frequency and output level by using the soft keys

and data input keys:-

[Gen 1/Gen 2] to select AF1, then, [FREQ][n]....[n][kHz/Hz]

[LEVEL][n]...[n][V/mV/dBm]

then [Gen 1/Gen 2] to select AF2 if required, ....[.../dBm]

The FREQ [

] and [ ] and the LEVEL [ ] and [ ] keys can be assigned to AF generator

frequency and level. See Incremental adjustments which starts on page 3-62.

Either or both generators can be switched off to suit the test requirement. To disable a generator

select it using the [Gen 1/Gen 2] key to toggle between them. When the title of the generator is

highlighted on the display, press the orange[ON/OFF] function key. Repeated presses of this key

will toggle the ON/OFF action.

The shape of each audio generator output waveform can be either sine or square wave. This is

controlled by first selecting the audio generator as for [ON/OFF] control above, then pressing the

[Shape] key to toggle between the options.

Note that the audio generators are also used as modulation generators for the

receiver test signal generator. If both generators are set up as a modulation

source in the Tx test mode, switching to Rx TEST mode will show both

modulation generators in the OFF condition. Either or both generators can be

set up and turned on within the Rx TEST mode. The frequency, level and

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Aeroflex 2946A Instructions d'exploitation Page 63

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