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The Super J-Pole Antenna Calculator


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(Collinear Design)
A calculator for deriving the lengths of tubing to be used for the construction of a Super J-Pole Antenna.
The calculator can be used for designing a Super J-Pole antenna for just about any frequency or it can be used for the standard J Pole antenna by leaving out the top section.

The Super J Pole yields about 6dB gain + - over a 1/4 wave ground plane by adding one 1/2 wave section to the top of the regular J Pole with a matching section between the two.

The information on this page is not designed to give you complete construction details but to enable you to get the suggested lengths and basic information of the Super J Pole antenna.
It is suggested that you use 1/2 inch tubing (aluminum or copper) in the construction of the Super J Pole antenna for broader bandwidth.

Bottom Section Inches
Top Section Inches
Matching section Inches

Formulas used in J Pole calculator:
Longest Section - 8424 / FreqMhz = inches
Top Section - 5616 / FreqMhz = inches
Matching Section - 2808 / FreqMhz = inches

The Basic Super J Pole Antenna

The suggested spacing between the short bottom matching section and the longer bottom section is about 3 inches center to center or about 1 inch between elements depending on your construction.
A 1:1 balun is suggested at the base of the antenna consisting of about 5 or 6 coils side by side of coax air wound in a 5 inch circle.
Attach coax feed points on short and long side a few inches up from bottom (either side) and adjust up and down for lowest SWR and best match.
Note that most builders attach the center conductor feed to the longest side and the shield to the shortest side on the matching section.

Example for 146.00Mhz using the calculator:

Longest bottom section 57.69 inches
Top section 38.46 inches
Matching Section 19.23 inches

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