Specifications

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• INTRODUCTION:
The objective is to align variable elements in Kaval 20W 800-900 MHz power amps to optimize RF performance, and verify
performance against specifications. This procedure applies to amplifiers to be used together with external electronic fault
monitoring modules in Kaval BDA systems. Certain internal fault detection features are not aligned in such case and
these adjustments are set to positions which defeat these functions. Alignment of fault detection circuitry not necessary in
BDA applications are covered in another document.
The Kaval 20W power amplifier is a single stage Class AB linear power amplifier using a high power LDMOS amplifier
transistor. Compression point is about 20W, and intermod performance rivals that of similar amplifiers with 30W ratings.
This design is optimized for best intermodulation and minimum heat in multicarrier repeaters, not necessarily highest output
power in saturation. Due to the necessity of using microstrip matching elements at these frequencies, and the need to tune
the amplifier to various application bands, microstrip element lengths must be adjusted in some cases. The PCB design
includes easily cuttable “zipper links” in the microstrip stubs which allows tuning using a hobby knife. Care must be taken
when cutting links that the entire link is removed. A thin knife cut may leave copper slivers that may later reconnect and
detune the amp after exposure to vibration. For this reason, use the wider back edge of the hobby or putty knife, and
verify, using a magnifier, that the links are properly and permanently cut. If during adjustment, it is found that one went too
far, and a link needs to be restored, this can be easily done by solder bridging. At all times, do not apply power to UUT
unless both input and output are properly RF terminated. Be especially careful not to connect UUT with input and output
reversed since this unit has ample capability to destroy network or spectrum analyzers.
• EQUIPMENT:
The following equipment is needed for execution of this procedure.
q Scalar Network analyzer, 1 GHz capable. Analyzer must be normalized and calibrated per manufacturer’s instructions
prior to any test session and at 1 hour intervals thereafter.
q Termination calibration kit for above (type N)
q Spectrum Analyzer, 1 GHz capable, input dynamic range up to +25 dBm with input intermod < -60 dBc
q 50W 20 dB Attenuator good to 1 GHz. Type N.
q Multimeter
q 800-1000 MHz Splitter/Combiner, Isolation > 20 dB 800 MHz to 1000 MHz. (Narda 4322-2 or equivalent)
q Two 10 dB fixed attenuators
q Turret Attenuator with 1 dB resolution. 0-30 dB minimum range.
q Broadband Linear Power Amplifier, 3W, 800-100 MHz, (Mini-Circuits ZHL-1000-3W or equivalent.)
q Two synthesized signal generators capable of tuning over 800-900 MHz band with output capability of +5 dBm
minimum.
q Johanson capacitor trimming tool No. 8777
q Power supply cable with male Framatome “Jupiter” connector.
q DC Power supply capable of 2A at 24 VDC with variable current limiting.
q Customized Amplifier top cover with access holes drilled for access to C19 and R5
q Toggle press or other means for temporarily securing amplifier top lid during test. (You may use 4 screws in the
corners as an alternative.
q RF interconnection cables as required. Do not use between series adaptors between network analyzer and UUT RF
input or between UUT RF output and high power attenuator.
Note, for accurate output level measurements, be sure to offset any cable losses or attenuator variations from the output
reading. Output losses should be characterized to within 0.1 dB.