Model GS-2/3/4
ILS Glide Slope Antenna Array 328-336 MHz

Frequency Range: 328-336 MHz
Gain: 10 dBi
VSWR: 1.2:1 max
Polarization: Horizontal
Model Number: GS-2/3/4
Part Number(s): 1000-0579-202, 1000-0582-502, 1500-0149-203, 1000-0579-203, 1000-0579-204
NSN: 5985-01-048-0147

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SKU: GS-2/3/4 Category:



Glide Slope Antennas are used to provide vertical guidance to aircraft during approach and landing of an aircraft under instrument fight rules.


The Glides Slope Antennas are designed to withstand 100 mph wind, 1⁄2-inch radial ice, temperature range of -50oC to 70°C, and 100% humidity. All elements are equipped with de-icing heaters and thermostats.


Glide Slope Antennas operate on a frequency of 328 to 336 MHz on a nominal impedance of 50 Ohms and power up to 50 watts. A null reference glide slope antenna system is fed by two transmitters, one on the carrier frequency and the other on sideband frequency. A capture effect glide slope antenna is fed by an additional clearance transmitter. (Refer to FAA Handbook 6750.6 for more information on null reference and capture effect systems.) A null reference glide slope antenna system consists of two antenna arrays, an external RF network, and a 40-foot tower equipped with safety climbing rail and obstruction marking and lighting. A capture effect system is a null reference system plus an additional antenna array, 20 feet of tower and a clearance cancellation bridge.

Part Number & Description:

1000-0579-201/202/203 Glide Slope Antenna
1000-0578-203 Mounting Frame
1000-0563-201 40’ Tower Kit
1000-0563-202 60’ Tower Kit

Spec Sheet


Frequency Range 328-336 MHz
Impedence 50 Ohms
RF Power 50 Watts CW
Monitor Coupling -6 to -10 db over 328-336 MHz
Polarization Hoizontal
Cross Polarization

At least -25 dB as measured in front of the antenna and within +/- 25 degrees in azimuth of a vertical plane perpendicular to the reflector and passing through the center of the antenna array

Front-To-Back Ration More than 16 db
VSWR 1.2:1 Max over 328-336 MHz
Gain More than 10 dBi
Horizontal Radiation Pattern Between the upper and lower limit lines as shown in following table
Vertical Radiation Pattern

Symmetrical around 0 degrees elevation and decreasing smoothly in amplitude in either direction from 0 degrees elevation.

Dipole Phase Left and right dipoles with 20-30 degrees phase of center dipole
Monitor Stability Signal Level Constant within +/- 0.2 dB over the service condition range; track other antennas within 0.15 dB.
Monitor Amplitude Stability Test Max change from baseline is +/- 0.075 dB when heaters are energized.
Phase Stability Test Max change from baseline is +1.1 degrees, -0.4 degrees when heaters are energized.
Dipole Heaters Yes