Slim Jim antenna designer.

Slim Jim Antenna dimension calculator

Back to Antenna calculator overview.

On-line antenna designer. Calculate the required dimensions for a Slim Jim antenna construction for any given frequency.

Enter the required frequency in MHz and the antenna designer will calculate the dimensions of the elements as shown below.

Enter Frequency (MHz)

The Slim Jim antenna is an extended version of the J-Pole antenna, using the same matching stub principle. The length of the antenna is three quarter wavelength. This antenna design does not need a ground plane and is ideal for mounting inside PVC piping to protect it from the elements.

Performs very well and can be used for RX and TX purposes. It can be made from any common household wiring. The thicker the wire, the wider the bandwidth of the antenna from its center frequency.

Frequency calculations are based on radio waves traveling at the speed of light 299 792 458 meters per second.


A: ? mm

B: ? mm

C: ? mm

D: ? mm

E: ? mm

F: ? mm


A: ? inch

B: ? inch

C: ? inch

D: ? inch

E: ? inch

F: ? inch

1090 MHz Slim Jim Antenna

Side view: ADS-B Slim Jim

1090 MHz Slim Jim Antenna

Front view: ADS-B Slim Jim

Slim Jim Antenna Design

Above images show a Slim Jim built for 1090 MHz using this antenna calculator. Note: The gap specification is for a RX/TX antenna and will need slight adjustment using the top curve as well as the matching section for transmitting (NOT ADVISED!). For RX only, the gap "E" can (should) be as small as possible without making electrical contact.