Comtech EF Data LTT1450G - Manual (Page 16)

Installation LTT1450G Ku-Band Loop Test Translator
Page 2-4 TM063 - Rev. 1
This is a -15 dB sample of the received output signal to goes to the SMA connector on the front
panel.
RF Input
The RF input to the Ku-Band converter module comes from the rear panel N-type connector.
RF Output
The Ku-Band translated output is routed from this port back to the rear panel N-type connector.
+15 Vdc
+15 Vdc which powers the Ku-Band PLO is also routed to this pin to provide drain current for the
FET mixer in the converter.
-VGS
The -VGS pin is the gate voltage for the FET Mixer. A potentiometer on the up board allows the
gate voltage to be adjusted during alignment to provide proper conversion gain, linearity and
third order intercept.
VCA
The VCA input pin is the port that the attenuator control current is applied. Current of 0 to 30
milliamps is typical for 0 to full scale attenuation. This current is derived from the D/A converter
on the microcontroller
2.5.3 Micrcontroller PWB AS/1030
Key elements of the microcontroller board are the serial interface, non-volatile memory, 12-bit D/A, 8-
channel 8-bit A/D, Negative voltage inverter and digital and analog positive voltage regulators.
The following various adjustments are found on this board:
R27 Zero adjustment 12-bit DAC
R28 Span adjustment 12-bit DAC
R29 -10 VDC Regulator adjustment
R24 -2V FET gate Bias Adjustment (X-band converter amplifier, VGS-X)
Note: Adjustment of zero or span potentiometer will invalidate the calibration on all bands. Also, no
attempts to adjust gate bias should be attempted by unqualified persons. Gate voltages are set to
provide the required gain, compression, stability and flatness of those channels which employ FET
mixers.