monopole 433MHz antenna length

[@artnoll]

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[@paulkazjack]

Hi nice test! What transmitter power did you use?

[@marcelpost4052]

The transmitter output power from the hand-held unit is around +4dBm [radio.setPowerLevel(0)] , then a further reduction with the 30dB attenuator puts the power sent to the antenna somewhere around -26dBm (around 2.5uW). The transmitter at the base station always sends the confirmation packet at 100mW.

[@paulkazjack]

When calculating antenna length do you *.95 for 'in air'? So 300 /433/4*.95. thanks

[@marcelpost4052]

Yeah, that's a good rule of thumb. It depends a bit on the change in velocity factor due to the outer insulation of the wire, which becomes a bigger factor as you're working with higher frequencies (868,915, 2.4, etc..). I'm sure that if I were to re-do the test with 16.1, 16.2, 16.3cm etc.. I might get an even better distance at some point, but this was just to demonstrate how much the distance varies if you're not cutting the length close to the optimum value and also to show how you can find out the optimum antenna length with just two radios and a bit of running around in a park.. :-)