User guide

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5: Description of System
TracStar750 / AvL Model 750 iMoVSAT three-axis positioner is used as an example. Note that fundamental
operation of all Roto-Lok positioners are identical relative to vehicle mount design. Minor changes exist in
Fly- Away systems relative to reflector removal, POL rotation/operation and the number of cases provided for
the antenna system proper. Note also the .75M antenna is the only antenna provided by either company that
does not have gas struts or stabilizer bars for positioning and stabilizing the antenna boom assembly.
General
The Model TracStar750 / iMoVSAT antenna system is an elevation over azimuth positioner featuring the simple,
rugged Roto-Lok® drive system that produces very low backlash, high stiffness, and high reliability. It is driven by a
low backlash gearbox with DC motors and all drive components are high-strength steel encased in lubricated-for-life
housings, resulting in the most reliable, no-maintenance system with the minimum of weight. The reflector is a 75 cm
equivalent Channel Master illuminated by a corrugated horn. The options for the placement of the transmitter vary
depending upon the size: A 1 - 4 watt BUC can be installed on the feed boom.
RF System
The offset reflector/feed system produces co-polarization patterns that easily meet the FCC Section 25.209
requirements beyond 1.72 degrees in the transmit band and 1.95 degrees in the receive band. It is also fully compliant
with the ITU Recommendation for international use.
Roto-Lok Drive System
The patented Roto-Lok drive system utilizes highly reliable aircraft control cables in a redundant configuration to
achieve a lightweight, very stiff drive system with zero backlash. This high-tech performance is achieved using low-
tech components - by simply wrapping the cable around the drive capstan several times before wrapping the larger
drive drum. This method results in a minimum free-length of cable. The load cable on the main drum is exponentially
reduced as it is wrapped around the drum. Therefore, the total elongation of the cable under load is minimized. The
Roto-Lok system has up to 10 times less backlash than that of comparable gear systems. The cables are pre-
tensioned and spring-loaded at the main drum attachment point, which eliminates backlash at installation and from any
unexpected cable stretch in the future.
Pedestal