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Reduced Price New 3-Band HF Big Thunder Yagi Antenna, 20/15/10M, 7 elements Expand

Cushcraft 3-Band HF Big Thunder Yagi Antenna, 20/15/10M, 7 elements


X-7 by Cushcraft


Cushcraft X-7 Big Thunder Triband Yagi antennas set higher standards in both radiating performance and mechanical reliability.

More details

The product development team has employed the latest computer modeling technology to achieve a superior electrical design as well as elegant new mechanical hardware and assembly techniques. Each mechanical component was designed to 100+ mph wind survival with a 1.25 safety factor.

Traps were eliminated from the high current driven elements and reflectors using the new 4L Log Cell design, which yields virtual monoband performance and maximum power handling capability. Traps are employed only in the lower current directors for increased gain and sharper pattern. The result is a truly high performance antenna which will easily handle the legal limit.


  • New High Efficiency Computer Optimized Design for Maximum Gain and Ultra Clean Radiating Pattern
  • New 4L Log Cell Driven Elements for better VSWR Bandwidth
  • 100+ MPH Construction for Best Reliability and Long Life
  • Trapless Driven Elements and Reflectors for Reliable Power Handling


Cushcraft marketed its first 10-15-20 meter tri-bander in 1976. The antenna was updated mechanically and re-introduced as the A4 in 1980. The A4 evolved into the A4S when all hardware was changed to stainless steel.

The ATB-34, A4 and A4S models became the most popular 18-foot tri-bander worldwide. In 1997 the A4S was evaluated for performance using the latest antenna design software. Computer analysis showed potential improvements were possible through the use of a log periodic call for a driven element: The X7 was born!

The log periodic cell feed is the only commercially available feed system with inherent foward gain over a dipole. By properly spacing the reflectors and directors, and input impendance of 200Ω was achieved on 10, 15 and 20 meters. A 4:1 quadrifilar Guanella type ferrite balun was designed to provide 50Ω match at the X7 feedpoint.

The mechanical construction of the X7 was designed using Yagi Strength® (YS) software. A safety factor of 1.25 was used to guarantee an added cushion of safety over 100 mph rating of the boom, elements and hardware. All tubing for the boom and elements is 0.058 inch wall. The element and boom brackets are constructed of 6061-T6 extruded aluminum. All hardware is stainless steel.

On-the-air performance of the X7 yields an excellent radiation pattern, broadband low VSWR and minimal trap loss.

Cushcraft has developed a new manufaturing equipment to improve the quality of our products. Our products are now designed and constructed to a higher level of quality than ever before.


Frequency Coverage10, 15 and 20 meter bands
Total Elements7
Maximum Gain @ One Wavelength above ground20M: 12.5 dB @ 14 degrees
15M: 13.0 dB @ 12 degrees
10M: 12.9 dB @ 14 degrees
Maximum Front-to-Back Ratio30 dB
Elements per Band3
Minimum VSWR1.1:1
VSWR 1.5:1 Bandwidth20M: 600 kHz
15M: 750 kHz
10M: 1700 kHz
Longest Element11.33 m
37.2 ft
Turning Radius6.09 m
20.0 ft
Boom Length5.49 m
18.0 ft
Boom Diameter6.35 cm
Maximum Mast Diameter OD6.35 cm
Maximum Wind Survival> 161 kmph
> 100 mph
Maximum Wind Surface Area0.73 m²
7.9 ft²
Wind Load @ 129 kmph or 80 mph90 kg
202 lbs
Maximum Power Handling2000W
Design Safety Factor1.25
Weight27.2 kg
60 lb

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