23
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 - 80 mA to +80 mA. At currents beyond these values
the operating point will be shifted and IM-products will be rapidly increased. If a value of +
100mA is exceeded, the safety devices will switch the amplifier to STBY mode.
5.3.1.
AUTO or MANUAL
There are two possibilities of operation mode in OM4000A – AUTO or MANUAL. Normally, when
you are using CAT interface connection between TCVR and PA, in AUTO mode PA will tune
automatically to the TCVR frequency. If you do not have or use CAT connection, you will use
MANUAL mode. You must manually select proper band and segment, corresponding to TCVR´s
band and frequency. Then OM4000A will tune automatically to this manually selected
band/segment.
5.3.2.
Manual tuning instructions
The OM4000A has been design to deliver maximum output power at 50 Ohms load. Parameters
for PA auto tuning using real 50 Ohm loads are stored in the memory (
factory default
). To deliver
maximum output power to a real load you need to adjust the tuning according to your real
antenna impedance.
This has to be done manually in TUNE mode
(
see 5.3.3. for details
). First
off all PA must be switched on.
1.
Set the multimeter switch to the
HV
position
2.
Set the OPR/STBY switch to the
STBY
position
3.
Press the
ON
button
Summary of Contents for OM4000A
Page 28: ...28 7 1...
Page 29: ...29 7 2 Example of connection for ELECRAFT...
Page 30: ...30 7 3 Example of connection with Yeasu...
Page 31: ...31 7 4 Example of connection with antenna switch and BPF...
Page 32: ...32 7 5 Example of connection USB micro KEYER II with IC7800 or IC7700...
Page 33: ...33 7 6 Example of connection USB micro KEYER II with another Icom...
Page 34: ...34 7 7 Example for connection USB micro KEYER II with Yeasu or ELECRAFT...
Page 35: ...35 7 8 Example of connection PA with MicroHAM MKII MK2R etc with CI V output...
Page 36: ...36 7 9 Block Diagram of the OM4000A Power Amplifier...
