HELICAL ANTENNAS

Helical antennas radiate circular polarization. They are easily fabricated and operate over narrow or moderate frequency bandwidths. Seavey Engineering uses helical antennas as feeds and as complete radiating systems.The following are examples of some directional circularly polarized antennas using these techniques.

Model 8357-800 - Four-Helix Array Antenna
This antenna operates in the INMARSAT satellite communications frequency band of 1525 - 1660.5 MHz. It is configured as a set of four 24 inch long helices mounted to an aluminum frame and connected together with a Wilkinson 4-way power combiner. It interfaces with any standard camera tripod for positioning. Handling up to 70 watts of RF power, this antenna can be used as part of a portable satellite communications link. The helical elements stow in a carrying case for transportation.
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Model 8357-800 4-helix Array

Model 8613-850
13.4 dBic Gain

Model 8613 Series - L-Band Helix Antennas

These are simple helices for use in fixed-site L-band satalilite applications. All have an axial ratio less than 2 dB, can handle up to 70 watts CW with a frequency range of 1525 - 1660.5 MHz. The sealed construction uses a polycarbonate radome. An SMA jack connector is standard; an N jack is an option. Diameter is 2.38 inches. These antennas are available on special order with left-hand polarization sense.
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Model 9610-800
VHF 12.8 dBic Gain

Model 9610-800 - VHF Helix Antenna

100 - 160 MHz. 6.0 - 12.8 dBic gain. This very large 8-turn helix has right-hand circular polarization with an axial ratio less than 2 dB. It is15-feet long with a 28 inch pitch diameter. The circular cup reflectors are 6-feet in diameter. The assembly weighs 150 pounds.
Model 9610-810 is identical but has left-hand sense.

Model 8617-810 - High Gain UHF High Power Helical Antenna

For uplinks to UHF satellites, this antenna operates from 236 - 330 MHz with right-hand circular polarization with a gain of 12 to 17 dBic. Overall length is 10 feet. A special perforated metal cup reflector increases gain and reduces sidelobes. The antenna comes complete with an elevation/azimuth pipe mount allowing for elevation adjustments from horizon to 65°. Equipped with a type N connector, this antenna can handle up to 1 KW of RF power.
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Model 8617-800
UHF 12 - 17 dBic Gain

Model 8617-800 - High Gain UHF Helical Antenna

This antenna is similar to the Model 8617-800 except that it covers the 310 - 400 MHz frequency band and has an overall length of 7 feet.

Model 9339-800 - DARS Helical Antenna

This helix operates in the DARS frequency range of 2.31 - 2.36 GHz, has 6.5 dBic gain with a 72° beamwidth.

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