TMA2Q/LPC2Q Quadrature Tower Mounted Amplifier Instruction Manual
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III. Operation
A. TMA2Q Tower Mounted Amplifier
The TMA2Q has no operating controls. Power for the TMA2Q is supplied by the LPC2Q through the “CCW” and
“CW” circuit coaxial cables. When power is applied to the TMA2Q through the LPC2Q, and the coaxial cables are
connected, the green LED on the TMA2Q power supplies will illuminate. The LEDs are not visible when the cover
is on the TMA2Q during normal operation. Remove the cover to view the LEDs during circuit verification and
troubleshooting.
B. LPC2Q LNA Power Coupler
The LPC2Q has two internal power supplies, each equipped with a resettable PTC fuse. These power supplies are
controlled by the two On/Off switches located on one end panel just above the coaxial dc power jack. The
internal power supplies provide power to the TMA2Q power supplies through bias-tees and the interconnecting
coaxial cables.
To operate the TMA2Q/LPC2Q after all RF and power cable connections have been made as described in the
Installation section, move the power switches to the On position. A green light emitting diode (LED), located
immediately above each On/Off switch on the LPC2Q, illuminates when power is turned on. If the LEDs fail to
illuminate, check the power supply, power cable and connector. The end panel LEDs indicate only that power is
applied to the LPC2Q power input circuits and do not indicate that power is being supplied to the TMA2Q. See
above.
C. Callisto Setup
There are two areas of the Callisto setup that need to be tailored for use with the tower-mounted amplifier
system: 1) Callisto gain setting; and 2) frequency range. Only the settings are provided below; refer to the
Callisto Software Setup Guide for specific procedures {
Callisto
}.
Gain: The Callisto gain is specified in the Callisto configuration file
callisto.cfg
by adjusting the PWM value in
parameter
[agclevel]
. The range is 50 to 255 with 50 corresponding to minimum gain and 255 corresponding
to maximum gain. When used with the TMA2Q/LPC2Q, the gain value typically will be set around 100 to 120.
Experimentation will be needed to find the best value, which may be outside this range. Higher gain settings
decrease the Callisto instrument noise figure but increase the possibility of receiver front-end overload.
Similarly, lower gain settings increase the Callisto noise figure but decrease the possibility of overload.
Frequency: The Callisto frequency range is specified by two settings. First, the frequency range is specified in the
frequency file
frqxxxxx.cfg
, where xxxxx is an arbitrary user assigned numeric value. Typically, the range is 50 to
500 MHz in 200 channels with a sweep rate of 4 sweeps/second. This provides approximately 2.3 MHz
resolution. Higher resolution can be attained by using more channels at a slower sweep rate (the product of the
number of channels and sweep rate should not exceed 800). However, it may be necessary to block the FM
broadcast band, television channels or other frequencies from the frequency file due to radio frequency
interference.
