Antennas

If you need to put the antenna away from the board, outside a housing or replace it with a directed one you need to attach a shielded cable instead of the standard wire.

The shield should surround the inner wire as close as possible after the connection to the antenna port. Everything from the end of the shield works as antenna!

The inner wire is soldered to the pin of the (then removed) wire-antenna and the shield to the third pin, so there is one unconnected pin between antenna and shield.

Pictures follow later...

Antenna Lengths for Various Frequency Radios

Antenna length is not crucial, these are approximate sizes for 1/4 wavelength whip antennas (pieces of wire) used on RF12 radios at various frequencies

  Band    Length

415 Mhz   170 mm
868 Mhz    85 mm
915 Mhz    80 mm

(From TikiWiki - Created by MarvinGS)