Cloverleaf

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This document outlines the construction of a Cloverleaf antenna for the 902-928MHz ISM band.

Final result of the CL build.

Summary

A cloverleaf antenna is an omnidirectional, circularly polarized antenna, constructed of three 105 degree arcs spaced 120 degrees apart, with each straight leg measuring a quarter wavelength. The antenna was built using the instructions here: http://www.rcgroups.com/forums/showthread.php?t=1388264

The antenna is soldered directly to a short length of RG-316 coax, with a SMA male connector at the end.

The total build time for this antenna was approximately 45 minutes.

Bill of Materials

Part Quantity Unit Cost Total Cost Source
SMA Male Connector 1/5 $2.51 $0.50 Dealextreme
RG-316 Cable 5"/50' $16.05 $0.13 eBay
Pencil 1 ~$0.50 ~$0.50 Office Supply Store
18ga. Solid Core Wire 39"/100' $6.89 $0.23 Radio Shack
Total Price ~$1.36

Photos

Results

Post-optimization return loss (left), and VSWR (right).

After tweaking the angles of the antenna, the VSWR is below 1.2 over the 900MHz ISM band (902-928MHz) with a VSWR of 1.08 at 910MHz, resulting in an efficiency of >99.3% (calculated by the formula Power % = 100 * (1 - ((SWR-1)/(SWR+1))2). The antenna weighs 15.9g.