70cm Jpole

Project Status

Flight Tested on S08L01

Problem Statement

The Big Red Bee Amplifier is a high power RF device. Simple whip-type antennas are not effective without ground planes and ground planes are difficult to construct at 100,000ft :)

The j-pole antenna is a half wave radiator with a quarter wave stub which serves as a ground point and thus is a good choice for an omni-directional antenna. The antenna is easily made from twin lead TV transmission line and a short piece of coaxial cable. The antenna is rigid enough to maintain a horizontal polarization throughout the flight.

70cm_jpole_photo.jpg
70cm_jpole.jpg

Dimensions

  • The main radiator is 51cm long
  • The stub is 15.5cm long
  • The feedpoint is 1.25" from the bottom
  • A solidworks diagram has been created (see above right)

Performance

  • At 441.050Mhz the SWR is measured at 1.2 :)

Project Contact

Jasper Nance