Build a DIY 70 cm / 440 MHZ J-Pole Antenna
Here is an inexpensive J-pole antenna that is easy to construct. In about an hours time, and about $10 worth of materials, you can have a great performing omnidirectional j-pole antenna.
This antenna is based on the same ideas as my 2 Meter J-Pole construction plans.
The j-pole antenna is basically an end fed half wave dipole that uses a 1/4 wave shorted matching stub as an impedance transformer. The j-pole antenna will yield slightly less than 3 DB of gain omnidirectionally.
The material I chose to build the j-pole antenna was 1/2 inch copper pipe used for plumbing. Here are the plans to build a 70 CM J-pole antenna:
Build a 70 cm / 440 mHz J Pole antenna
The above dimensions for the J-pole are in inches, and aren’t typical for a 440 mHz. J-pole antenna. This is what it took for me to get the SWR low. Measurements on overall length, and stub length are from the centerline of the separation pipe (horizontal) to the top of the antenna. The Connect at measurement is 1 1/2 inches from the top of the horizontal member to the point of connection. The distance between the main element of the j-pole centerline and the tuning stub centerline is 0.75″.