Rotor Blade Effects on L-Band Signals Received by Helicopter Antennas Mounted Above the Rotor Blade: CW Experiments
Abstract
Rotor effects on L-Band signals received by helicopter antennas have been examined experimentally. CW data for two receiving-antenna locations above the rotor blade, viz. at the turning axis of the blade and on the tail, is presented. This data shows the amplitude and phase variations to be expected as a function of the direction of the incident signal. The effects of counterpoise size and height above the main rotor are also studied. In general, it is shown that the signal variations were typically < + or - 3 dB for polar angles of arrival thata < or = to 70 deg; but that for greater angles, the signal amplitude changes by as much as + or - 7 dB. For thata >90 deg (an arrival angle obtained, for instance, during a turning and banking maneuver) signal levels can decrease by -15 dB and the phase variation can exceed 180 deg.. The tail location appears to be a better choice for the antenna than the center location. A worst-case analysis of CW rotor effects is presented in Appendix I. Appendices II and III contain some of the data measured at both antenna locations and should be referred to for a better understanding of the signal variations involved.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1975
- Accession Number
- ADA016866
Entities
People
- C. M. De Santis
- F. Schwering
Organizations
- United States Army Communications-Electronics Command