OM POWER OM2000A+ Manual page 29

M-TUNE means entry to the manual tuning mode. It allows fine tuning of the PA, especially in the case when
antenna impedance is different from real 50 Ohms. For proper adjustment we need to show Screen current (at
least). Press M-TUNE. New screen is visible. Slides on the left and right side represent both variable capacitors.
Adjustment process: Move TUNE left or right until maximum of FWD power reached. Then move LOAD carefully
so that Ig2 Screen (I Screen on the display) current will be not higher than 20mA. Optimum means maximum
FWD power and Screen current between 0– 20mA for the used power output. Repeat more times. When using
lower power, Ig2 can go to negative values.
Result of the tuning process is optimal, when PA was tuned to the maximum forward power and Ig2 current stays
in the range from 0 to +20mA. At that time maximum efficiency and optimal linearity are achieved. This applies
to each power application. It is not necessary to retune the PA, if we decrease the output power. The PA stays in
linear mode with little lower efficiency. If we increase the output power, retuning is necessary only if Ig2 exceeds
+20mA.
Now one example from real situation. First we will check driving power from the transceiver. Stay in STBY mode,
press PTT and apply RF power.
After adjustment press SAVE for writing values
Type of supported TCVR and working
to the memory and press EXIT.
frequency are visible on the display.
Repeat adjustment process for other segments
/ bands.
Measured driving power is 53 Watts.
Type of supported TCVR and working
frequency are visible on the display.
Now switch to OPER, press PTT and apply RF
from TCVR. See the following picture.
AUTO LED is ON.
AUTO LED is ON.
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