RF Concepts LLC PA-77DF User Manual
55
5
DOCNUMBER 9500
Document Issue 1.1
February 2010
February 2010
Page 5–7
RF Concepts, LLC
Alpha 9500 Linear Amplifier User Manual
Product Release 1
Operating the Amplifier
5.3 Tune the Amplifier
!
IMPORTANT
•
Do not attempt to tune the amplifier until you read this entire
section. Then follow instructions carefully.
section. Then follow instructions carefully.
•
During any tuning operation, it is important that you monitor grid
current and gain. Even at SWR >2:0:1, where full output may not
be achieved, you must still keep grid current and gain within
limits. You normally should not need over ~60 W input to drive the
amplifier to full output.
current and gain. Even at SWR >2:0:1, where full output may not
be achieved, you must still keep grid current and gain within
limits. You normally should not need over ~60 W input to drive the
amplifier to full output.
The Alpha 9500 has an autotune feature for tuning to the desired
frequency. You can use this feature or turn it off and manually tune the
amplifier.
frequency. You can use this feature or turn it off and manually tune the
amplifier.
Your goal in tuning the amplifier is to maximize output power for a given
input power. At SWR > 2.0:1, this normally becomes difficult. You can
load a high SWR, but keep in mind as you approach full output that there
is great stress on the transmission line, connectors, and antennas. If you
use an antenna tuner, also keep in mind that high voltages and circulating
currents may exist between the tuner (also inside the tuner) and the
antenna even though the amplifier sees a good load.
input power. At SWR > 2.0:1, this normally becomes difficult. You can
load a high SWR, but keep in mind as you approach full output that there
is great stress on the transmission line, connectors, and antennas. If you
use an antenna tuner, also keep in mind that high voltages and circulating
currents may exist between the tuner (also inside the tuner) and the
antenna even though the amplifier sees a good load.
Remember
REMEMBER
A properly tuned amplifier has the following properties:
•
Full legal power output. For voltage SWR <2.0:1 this is 1500 W
(with 40–60 W drive). For SWR > 2.0.1, full power may not be
possible but the other tuning indications are the same.
(with 40–60 W drive). For SWR > 2.0.1, full power may not be
possible but the other tuning indications are the same.
•
Grid current in green zone (normally 40 mA; at >100 mA, the
system alarms)
system alarms)
•
Gain indication in green zone
•
Plate current in green zone (1 A at 1500 W; at >1.2 A, the system
alarms)
alarms)
(Optional) Changing
antenna settings
antenna settings
You can optionally change to other than the default antenna or use two
antennas simultaneously.
antennas simultaneously.
Procedure 5-2 (Optional) Change the antenna settings
Step 1
.
Step 2
To change the default antenna to a different port for all User 1/User 2
memory bank settings:
memory bank settings:
2a
Press User 1 or User 2 so that the memory light is on.