11
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 OM2200 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.
Before starting tuning you have to check if the right antenna or a 50 Ohms load
resistance is connected at the antenna output!
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.
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.
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.
