External Antenna on Mica boards

For many applications, the short range of the built-in antenna on Mica motes is suboptimal. This document describes how to install an external antenna.

We've experimented with several antenna designs. A quarter-wave whip antenna made out of solid core wire works reasonably well, although it does not provide great uniformity and it is quite large. Some motes in the NEST kits delivered in February, 2002 came with external can antenna -- basically it is a quarter wave whip, coiled into a helix, and embedded in a plastic can. These antennas can be purchased from Linx Technologies and the product description can be found here.

The installation procedure is quite simple:
  1. Desolder R28. The quickest way is to put a bead of solder on the iron, touch it to both contacts of the resistor, and with the soldering iron just push it off the board.
  2. locate the mounting hole in the very corner of the board, right next to R28. Put some solder in it. Solder on the antenna. Make sure that the contact between the antenna and the board is good, it is quite easy to get a cold solder joint between the antenna and the board, which degrades the performance drastically. You can test the quality of the joint by trying to rotate the antenna, if it feels solid, you're fine. If not, heat up the joint, and use more solder as necessary.
When you're finished, you may end up with a mote looking like this:
Last modified: Fri May 10 14:23:15 PDT 2002