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