User's Manual Part 2

- Calibration steps

STEP 1. Close the input and the output of the module by connecting them to a 50

ΩΩ

Ω dummy load

and connect the spectrum analyser through a directive sample, in order to look for self-oscillation of the

module, if any (anyway the module has been designed so that it would not self-oscillate even if totally de-

coupled, without any input or output load).

STEP 2. Check the voltages of the polarisation circuits without assembling the transistors first:

connect the 32V power supply to the proper turret by means of a fastening screw, then give power and check

data:

- the stabilised voltage on the zener diodes DZ1 and DZ2 is about 15V compared to the ground;

- the stabilised voltage on the zener diodes DZ3 and DZ4 is about 6.8V compared to the ground;

- the voltage on the pads to which the gates of the LDMOS transistors will be soldered (R23 and R24

resistors side) changes from 0V to a maximum value of about 6V when moving the relevant trimmer (R7-R8).

STEP 3. Check the work of the protections.

- Set both trimmers so that there is a value of about 4.5V on the pads of the gates;

- solder some wire to the pad between the two LEDs, next to the serigraphy of the input hybrid H1;

- in order to check the work of the protections aboard, a power of about 4V has to be supplied to the wire,

for example by touching with it the reophore of C23 or C24 which is not connected to ground; the two red

LEDs will immediately light up and the two RF transistors will be switched off at the same time: the polarisation

current (2A) will decrease to 0 and of course the gain curve displayed by the spectrum analyser will decrease;

- after this it is important to restore the position of the two trimmers for the minimum voltage! Then

disconnect the 32V power supply.

STEP 4. Fastening of the LDMOS transistors: after properly cleaning the plate surface, smear a thin

layer of silicone fat on the lower side of the flange of the MOSFETs, fasten them to the heat sink and solder

the gate first, then the drain. Solder the two 13pF (ATC) chip capacitors and above them the two 1-5pF

Solder a wire