Comtech EF Data LTT1450G - Manual (Page 13)

LTT1450G Ku-Band Loop Test Translator Installation
TM063 - Rev. 1 Page 2-1
Section 2 - Installation
2.0 Installation Requirements
2.1 Mounting
The Radyne Loopback Test Translator product line is designed for either a rack mount installation or
bench top use. Rack mounting the test translator can be accomplished by securing the chassis front
panel with standard rack mount hardware. The welded construction of the test translator chassis makes
this a secure method of installation. Alternately, the chassis is equipped to accept standard rack
mounting slides if so desired. In a permanent rack installation, the adhesive rubber feet on the underside
of the chassis are intended to be removed if they interfere with other equipment. Ventilation of the
chassis is via side vents, so stacking the test translator with other chassis’ does not pose a problem. It is
assumed however, that the ambient temperatures in the rack will be maintained to less than 50 degrees
Celsius.
2.2 Power-up
Primary power may be applied via the AC line receptacle. Unless indicated otherwise, the test translator
may be operated from 100 to 240 volts AC at 50 to 60 Hertz. Turn the power switch on the Power Entry
Module at the rear panel to the ON position. At this time, the green power LED will illuminate and the
red LO fault will also illuminate momentarily. Note that if the test translator is being powered up from a
cold start, the momentary LO fault may last for a few minutes and should clear after the internal
ovenized reference oscillator stabilizes on frequency. It is not uncommon for the cold ovenized oscillator
to be off by as much a hundred hertz. Once stabilized (20 minutes), the ovenized oscillator will be
accurate to better than
±
0.005 ppm. The test translators are designed for continuous operation. The
units draw little power (less than 20 watts) and may be left powered-up indefinitely.
Shielded cables with the shield terminated to conductive backshells are required in order to meet EMC
directives.
Cables with insulation flammability ratings of 94V0 or better are required in order to meet low voltage
directives.
2.3 Apply Signals
Apply the transmit signal to the TX RF input port in the good operating range of -5 dBm to - 25 dBm.
Good operating range is defined as signal levels that will guarantee a linear response with low
intermodulation and spurious content. An input level of -10 dBm is considered to be ideal. If multiple
carriers are to be translated simultaneously, it is recommended that the total power not be greater than -5
dBm for the same reasons. The test translator can be interfaced directly with most upconverter outputs.
When interfaced to an SSPA or TWTA, attenuator pads and/or directional couplers may be used to
attenuate the power of the signal to a good operating range.
Signal type may be CW or modulated for set-up. A CW signal has some advantages for use in testing
integrity of the hardware to be looped back. Naturally, a CW signal could never be used to check the
performance of the transmit and receive hardware over a satellite. But, with the test translator, a CW
signal can be used to test the stability and phase noise of the synthesizers in the up and downconverters.
Test translator phase noise is typically 20 dB better than most synthesized converters and as such
should never contribute to any noise appearing close to the carrier.