I have a very remote cabin at 1000m (3000f), where I have close to no phone reception, so lately I have been trying to research as much as I can fathom of radio basics, but still without being able to conclude on anything with regards to what kind of antenna design is the optimal for my usecase and why it would be the right.
I was thinking of buying a parabolic antenna, directed at the closest tower down in a valley some 5km away, after reading up on various types. As repeaters are illegal to use (unless you are a phone company) in Norway, I was planning on just connecting (via RG58+SMA) the roof top antenna to a whip in the main room of my cabin. Hopefully that would enable us to make calls inside at this remote location.
Greater directionality can be obtained using beam-forming techniques such as a parabolic reflector or a horn. Since high directivity in an antenna depends on it being large compared to the wavelength, narrow beams of this type are more easily achieved at UHF and microwave frequencies.
As GSM (900 MHz) is in the UHF range, a 60cm x 90cm parabolic antenna with a gain of 16 dBi seemed like a great fit.
But then I found a Yagi-antenna with a gain of 28 dBi(!), and I was a bit dumbstruck. The way I understood the thing with gain was that it was closely related to directionality: more omnidirectional would mean less gain and vice versa.
If a parabolic design had greater directionality, how could a smaller (in surface) Yagi still have a higher gain?
Obviously, I am not a professional after using a few hours reading up on quads, dipoles and whip-designs on Wikipedia, but I would like to understand how the things I buy work on rough level, so hoping you'll cut me some slack :-)