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Some random notes.

Coiled Antennas

User:Earthpatrol had a broken 915MHz antenna. I features a coil inside the rigid whip antenna casing. The coil consists of 28 windings, with 3mm inner diameter and .6mm thick copper wire.

The calculation results in: 316.67mm wire length. This is pretty close to the 915MHz wavelength of 330mm. The remaining 16mm might be in the inacurracy of my measurement or an aditional peace of wire hanging out of the coil where the wire is connected to the inner conductor of the antenna coax cable leading to the SMA connector. Still it is interesting to remember. :)

The calculation was 3.6mm winding diameter times Pi, times 28 windings. Easy right? :D