Vca (External); Fsk - Metrix GX1010 Notice De Fonctionnement

4.5.1.2. Modulation Depth
Move the edit cursor to the INT MOD DEPTH field to set the modulation depth between 1%
and 100% in 1% increments. The maximum output (20Vpp EMF) cannot be exceeded and
clipping will occur if modulation attempts to drive the output beyond this limit. The
maximum generator output setting at which correct operation is maintained reduces from
20Vpp EMF to 10Vpp EMF as the modulation is increased from 0% to 100%.
4.5.1.3. Modulation Waveform
The default modulation waveform is squarewave because this permits the full frequency
range of the internal trigger generator to be used. Alternatively, a fixed 1kHz sinewave can
be selected by moving the edit cursor to the INT MOD field in the last line of the display;
the DIGIT keys or rotary control can be used to toggle the setting between SQUARE (at the
frequency set on the internal trigger generator) and SINE. Note that selecting SINE forces
the TGEN field to display 1·00ms 1·000kHz but the user setting is not lost and if INT MOD=
SQUARE is reselected the TGEN setting returns to its original value.

4.5.2. VCA (External)

With the cursor in the SOURCE field of the AM edit menu, set the source to EXT VCA.
Connect the modulating signal to the rear panel VCA IN socket (nominal 6kΩ input
impedance); a positive voltage increases the generator output and a negative voltage
decreases the output. Note that as with internal AM, clipping will occur if the combination of
generator setting and VCA signal attempts to drive the output above 20Vpp EMF.
External AM is achieved by setting the generator to the required output level and applying
the modulation signal (which can be AC coupled if required) at the appropriate level to
obtain the modulation depth required. If the generator output level is changed the
amplitude of the modulating signal will have to be changed to maintain the same
modulation depth. As with internal AM, the maximum output setting of the generator at
which clipping is avoided is reduced from 20Vpp EMF to 10Vpp EMF as modulation is
increased from 0% to 100%. Modulation frequency range is DC to 100kHz.
The generator's amplitude control circuit has four quadrant operation, allowing the
generator output to be inverted if the external VCA voltage is taken sufficiently negative.
Suppressed carrier modulation (SCM) can be achieved by applying a modulating signal
with a negative offset between 0V and -3V (depending on output level setting) sufficient to
reduce the carrier output to zero.
It is also possible to modulate a DC level from the generator with a signal applied to VCA
IN, as follows. Set the generator to 0Hz sine wave on the Main menu and +90° phase on
the Trigger menu. Select EXT TRIG (the default) and turn Trigger mode on with the TRIG
key but do not apply a trigger signal. The MAIN OUT is now set at the peak positive voltage
defined by the amplitude setting on the Main menu; setting -90° phase on the Trigger menu
will give the peak negative voltage. Select EXT VCA on the AM edit menu and turn AM on;
the DC level will now be modulated by the signal applied to the VCA IN socket.
4.6.

FSK

FSK (Frequency Shift Keying) mode permits fast phase-continuous switching between two
frequencies. All other parameters of the waveform (amplitude, offset, symmetry) remain the
same as the frequency is switched; for switching between waveforms where all parameters
can change, refer to HOP.
FSK can be controlled by either the internal trigger generator, an external trigger input, by
the front panel MAN/SYNC key or by remote control.
FSK mode is turned on and off with alternate presses of the FSK key; the lamp beside the
key lights when FSK mode is on. The FSK mode parameters (frequencies, trigger source
and internal trigger generator) are all set from the FSK edit menu which is selected by
28 - II GX1010