Model SPR-330
HF Log Periodic Spiral Antenna 3-30 MHz 5 dBi Omni

Frequency Range: 3-30 MHz
Gain: 5 dBi
VSWR: 2:1 Max
Polarization: Horizontal
Pattern: Omnidirectional
Size: 33′ H
Model Number: SPR-330
Part Number(s): 1500-0307-201
Military Nomenclature: AS-3476/G, AS-3477/G, AS-3478/G
NSN: 5985-01-058-1383

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The SPR-330 log spiral antenna is suitable for short range (0-300 miles) skywave circuits. The horizontal polarization permits operation over all types of soil without the need for a ground screen. The antenna operates over the frequency band of 2 to 30 MHz without need for a coupler. The designs permit operation from receiving applications to transmitting applications up to 50 kW PEP. Harsh environmental capabilities are achieved through appropriate material selection.


The SPR-230 antenna is designed using log periodic principles to achieve broadband performance while mounting over earth. At frequencies below 20 MHz, the antenna provides a broad, horizontally polarized beam directed at the zenith to accommodate short range skywave circuits. At higher frequencies the beam maximum occurs at lower elevation angles to accommodate longer paths. Each radiating element is a continuous length of alumoweld wire insuring long life noise free performance. The spiral curtain is supported by six radial catenaries which are pre-assembled from alumoweld strand and are supported at the center by a galvanized steel mast. The extremities of the radial catenaries are supported by aluminum towers. The military standard versions use wood poles instead of towers. Custom versions use counterweights to limit tensions and severe environments.


The antenna is elliptically polarized. In the northern hemisphere, the transmit antennas are normally polarized in the right hand sense and receive antennas are polarized in the left hand sense to accommodate the characteristic wave (lowest loss mode) in the ionosphere where reflection occurs. For longer paths utilizing lower radiation angles a circularly polarized wave is refracted by the ionosphere instead of reflected and the sense of elliptical polarization becomes unimportant.

Equipment Supplied:

Radiating element, radio catenaries, towers and guys, center support mast, balun transformer, resistive terminations, 6061-T6 aluminum towers.

Optional Equipment:

Obstruction lights, erection kit, repair kit, repair tool kit, wood poles, counterweights.

Spec Sheet


Power Capability, /1 Version 1 kW avg/2 kW PEP
Power Capability, /2 Version 10 kW avg/20 kW PEP
Wind Loading 140 MPH no ice, 90 MPH, 1/2 inch ice
Shipping Weight 2,500
VSWR 2.0:1 Maximum
Power Capability, /3 Version 25 kW avg/50 kW PEP
Height 33 Feet
Frequency Range 3-30 MHz
Gain 5 dBi Over Average Ground
input Impedance 50 Ohms Unbalanced
Shipping Volume 65
Azimuth Coverage Omnidirectional +/- 3 dB