Model 9392-800
Antenna Omni

Remote Monitoring Station (RMS)

Helical Array Antennas
Models 9370-820 and 9507-800

These innovative antennas were designed to receive L-band signals from the AMSC (101°W) and TMI (106°W) satellites. Model 9507-800 is used for the Solidaridad (109.2°W and 113.0°W) satellites.

The radiation pattern of the two helical elements in the hour angle plane (array plane) is determined by the element spacing and by the helix element pattern. For hour angles greater than 35°, the helix elements provide good discrimination against other L-band satellites.

Each element is fed into a hybrid. One hybrid port forms an on- axis beam, the other has an on-axis null whose off-axis peaks are arranged to be at the angle of the adjacent satellite(s). Therefore, the sum port receives the AMSC 101° satellite and the difference port receives the adjacent satellite.

Careful balancing of the array element signals results in isolation of at least 20 dB between the two signals. The antenna is mounted to a standard polar mount which automatically aligns the array plane to the Clark orbit plane. For TMI, each helix is 22 inches long and the element baseline is 40 inches. For Solidaridad, each helix is 27 inches long and the baseline is 50 inches.

This antenna effectively replaces two 3.7-meter parabolic reflectors which have equivalent angular discrimination. The result is an RMS antenna system cost savings of 90%.

Model 9392-800 - Helicopter-borne Helical Antenna

Mounted inside an aerodynamic radome, this antenna operates in the 1.2 - 1.35 GHz frequency range. It is left-hand polarized with a beamwidth of 60°, a gain of 11 dBic and can handle 100 watts CW.

Model 9171-810 - Helical Array

This six-element helix array is fed from a microstrip power divider. A radome covers each element. Operating in the 3.65 - 6.425 GHz C-band SATCOM frequency range, this antenna is used in mobile satellite systems aboard moving vehicles. It has a gain of 15 dBic with beamwidths of 12° azimuth and 70° elevation.

Model 9171-810
C-band Array

Model 9370-820
RMS Monitoring Station Antenna

Helix Feeds
Helices can be used as feeds for parabolic reflectors.

The following are some typical designs. For INMARSAT helix feeds, please see Page 103.

Model 8881-800 - Frequency 1.20 - 1.66 GHz. Receives the GPS L1 and L2 signals and operates in the standard L-band SATCOM range with right-hand sense.

Model 8231-890 - Frequency 1.365 - 1.375 GHz. Handles 400 watts PEP. Connector is an N jack. 3 inch diameter, 4 inches long, 4 inch square ground plane.

Model 9826-800 - Frequency 1.525 - 1.660 GHz. Retrofits standard Ku-band DSS antennas for L-band SATCOM.

Model 9203-810 - Frequency 4.0 - 5.5 GHz. Used with a 4-foot reflector in a telemetry application. 3 inches long, 3 inch diameter.