This document outlines the construction of a Cloverleaf antenna for the 902-928MHz ISM band.
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|
|Pencil||1||~$0.50||~$0.50||Office Supply Store|
|18ga. Solid Core Wire||39"/100'||$6.89||$0.23||Radio Shack|
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.