Centrad GF266 Manuel D'instructions page 28

Internal PSK modulation (int psk)
After selection, "HOP 180°" is displayed, and the cursor positions itself under 180° .
Set the phase shift between 0 and 360° using the thumbwheel switch [17], then press Valid [15].
A star is displayed between the frequency and function. From this time on, the output signal is shifted in phase by
the set value at the modulation frequency (internal 800Hz).
To quit the modulation function, press Modul. (Stop Mod.) button [14].
External PSK modulation (ext psk)
After selection, "HOP 180°" is displayed, and the cursor positions itself under 180° .
Set the phase shift between 0 and 360° using the thumbwheel switch [17], then press Valid [15].
A star is displayed between the frequency and function. From this time on, the output signal is shifted in phase by
the set value at the frequency of the VCF input signal [20] (TTL level).
To quit the modulation function, press Modul. (Stop Mod.) button [14].
The IN/OUT VCF BNC plug [20] is an input. The maximum allowable voltage before degradation is ± 60 V.
!
Electrical overload: Never apply a category II, III or IV measuring voltage to the inputs.
EXTERNAL FREQUENCY MEASUREMENT (counter)
When the generator is switched on, the cursor positions itself below the function.
Pressing the Function Counter button [9] selects the frequency counter.
If the cursor is not below the function, pressing the Function Counter button [9] twice selects the frequency counter.
After function selection, "Fext 0-25 MHz" is displayed, and the cursor positions itself below F .
Select your range using the thumbwheel switch [17]: 0 - 25 MHz or 25 - 100MHz, then press Valid [15].
"Fext Wait ..." , then "Fext No Signal" are displayed.
When a signal is present on the INPUT COUNTER BNC socket [19], the frequency counter shows its frequency.
The maximum allowable voltage at this input is ± 60 V.
The 0 - 25 MHz range is divided into 5 sub-ranges. The display is controlled automatically.
STORING A SETUP (Store)
Press % Duty / Store [13] twice. "Store (xx)" is displayed, and the cursor positions itself below (xx) .
Select a memory location between 2 and15 using the thumbwheel switch [17], then press Valid [15].
The setup (latest modification of all parameters) will be stored in the selected memory location.
RECALLING A SETUP (Recall)
Press Offset / Recall [12] twice. "Recall (xx)" is displayed, and the cursor positions itself below (xx) .
Select the memory location to recall (1 to15) using the thumbwheel switch [17], then press Valid [15].
The generator will use the setup stored in the selected memory location.
Note: Memory location (1) is programmed at the factory and cannot be modified.
Setup: sine,1 kHz, 2 Vcc, calibrated offset and duty cycle.
PROTECTION AGAINST REVERSE POWER SURGES
The generator is protected against reverse power surges that may damage the output stages ( 50 Ω OUTPUT and TTL
OUTPUT ).
When the current at one of outputs [21] or [22] exceeds the operating limit of the stage, the protection instantaneously
disconnects these outputs.
"WARNING OUTPUTS - Press VALID key" is displayed. After the fault has disappeared, pressing Valid [15] reconnects
outputs [21] and [22].
If the fault has not disappeared, the protection will trip immediately.
At outputs [21] and [22], the maximum allowable voltage is ±60 V peak.
[22] 50W OUTPUT ( Output 50W )
The generator output signal is available on the female BNC socket [21].
This output can be subjected to a permanent short-circuit without damage to the unit.
The Zo internal impedance is equal to 50Ω (Fig . 10) .
Zo and the Zi impedance of the connected stage form an attenuator with a ratio Zi / (Zo + Zi)
Example: Vout measured at no load = Vg = 10 V peak to peak
with Zi = 50Ω, we have:
Vout = 10x (50 / (50 + 50) = 5 V peak to peak
Vg
- 28 -
Fig . 10
Z
0
Vs
Z
i