I'd like to document the sizes of simple wire antennas to use with the JeeNode. Have been using around 85 mm for 868 MHz and they seem to work fine.
But what are the exact optimal sizes for 433, 868, and 915 MHz, respectively?
I can't seem to find a simple answer on the web.
Hi JCW,
The approximate lengths are:
433 = 173mm
915 = 87mm
These were measured from the ones supplied from HopeRF for their RFM12B DIP modules.
These are available on an old tutorial I wrote some time ago for the RFM12 (http://blog.strobotics.com.au/2008/06/17/rfm12-tutorial-part2/)
But calculated (rounded to single decimal):
433 1/4 wave = 164.7mm
433 1/2 wave = 329.4mm
433 full wave = 692.7mm
868 1/4 wave = 82.2mm
868 1/2 wave = 164.3mm
868 full wave = 345.5mm
915 1/4 wave = 77.9mm
915 1/2 wave = 155.9mm
915 full wave = 327.8mm
So there is a bit of difference to the ones supplied by hope (1/4 wave).
Thanks Stephen. I'll go with your calculated values: 433 -> 165, 868 -> 82, 915 -> 78 mm.
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