User Manual

In STBY, if WAIT-LED is on or the amplifier is OFF, the amplifier

is in bypass-mode and your transceiver is directly connected to the

antenna. Maximum allowed power in bypass mode is 400 Watts!

RF OUTPUT Bar graph – shows output power .

REFLECTED POWER Bar graph – shows reflected power from the antenna.

Maximum level is 350W otherwise amplifier switches to

STANDBY mode.

Ig2 Bar graph – measures the current of the second grid from -20mA to

+80mA.

HV/IP/TUNE Bar graph – measure the anode voltage, anode currency or tuning of PA.

5.2. Tuning of Power Amplifier

The OM2500 HF amplifier is operated in class AB. Thus it’s possible to obtain a maximum

output power at excellent linearity. For this purpose the amplifier has to be tuned carefully.

WARNING!

Before starting tuning you have to check if the right antenna or a 50 Ohms load

resistance is connected at the antenna output!

CAUTION

The operation of a mistuned PA will cause malfunctions, the increase of grid current

(the GRID-MAX-LED will light up) and problems with TVI/BCI.

CAUTION

The grid-current is shown with 2 LED diodes. It’s normal if the green LED is flashing or

may be shining a little bit during peak operation. If you overload the amplifier the

output power increases the grid current at very small rates and the red GRID-MAX-

LED is shining and the safety devices switch the PA to STBY. You must decrease the

input power.

CAUTION

In SSB mode you will have good output power if the green LED lights up a bit. The

current of screen grid is measured and shown in a Bar graph Indicator. The amplifier

has to be tuned in such a way that the current is between - 20 mA to +50 mA. At

currents beyond these values the operating point will be shifted and IM-products will be

rapidly increased. If a value of + 70mA is exceeded, the safety devices will switch the

amplifier to STBY mode.

1. Set the multimeter switch to the HV position

2. Set the OPR/STBY switch to the STBY position

3. Press the ON button

The amplifier is prepared for operation with the following automatic steps: