I was wondering about the lengths for the antennas mentioned on this page.
For 868Mhz is mentioned a length of 82.2 mm on this page. The length most often mentioned over the internet - as first result of the 1/4 wave calculation - is 86,5mm.
Searching a little deeper through the internet, i found that the antenna should be "a little shorter". Then they end up with around -1cm shorter or something around or more.
One page mentioned the physically effect that the wave is moving in chopper around 5% slower as the theoratical speed. If i substract 5% of 86,5mm i end up with the here mentioned 82,2mm.
I was very suprised about the different "approaches" for such a basic thing as antenna length every single . As most of the application over the internet seem to work somehow with all that different lengths, it seems to be just a fine-tuning thing.
Anyway, i think it would be nice to mention this details here because most people will wonder about the 82,2mm in the first view...
best regards
Jens