I have purchased a dipole 915MHz antenna here:
https://lowpowerlab.com/shop/product/193The unmodified antenna looks like if it's optimized for 868MHz. I would like to understand what I'm doing wrong.
I have soldered a u-fl connector and the polarity has been respected.
Now, here is probably an important thing: the cable length is 16.5cm (that's all I have).
On this thread
https://lowpowerlab.com/forum/rf-range-antennas-rfm69-library/alternative-pcb-dipole-designs-(433-868-and-915mhz)/, it says 915Mhz gives an ideal feedline length of 10.8cm. I don't understand how this number is calculated:
speedoflight / 915MHz = 32.76cm
So the post uses a magical /3 factor while all google links mention more 66% at 50 ohm for the velocity factor.
The length measurement on the post mentioned above doesn't seem to be super precise. And what about the length of the traces on the emitter board?
Anyway, even if the feedline length is not optimized, I would expect a lower deep not a shift.
Has anyone some good explanations?