I moved to an offgrid house with a 3G/4G repeater, with a short, enclosed directional antenna. It was wobbling and poorly mounted on an unstable wood plank at the base of a window, so I decided to fine-tune its placement.
I checked maps and azimuth for nearby public GSM antennas. The only realistic, nearby one (at about 2km) is indeed right in front of the window, however there is a small hill in between. Others are much farther and way under the horizon.
To my surprise the best result I got is when my antenna is the closest to the window glass, and more surprisingly, my SNR even improved when I placed it parallel to it, pointed towards the concrete side wall of the window, not towards the GSM pole which should be pretty much at right angle.
The concrete probably has rebar so it might create a loop, but I imagine it would certainly be grounded.
This really makes no sense to me and I am looking for an explanation (beyond black magic.)
My only guess is that the triple-glazing wooden framed window might be metal-coated, and it would "amplify" the signal, that the directional antenna catches laterally? Does this even make sense?
I know just enough about radio engineering so as not to trust myself too much and keep a low profile, so I also cowardly checked every angle with the antenna mounted on a tripod on my terrace (same height as the window,) with 5° increments.
No way, the best placement is the one shown on the picture.
- AFAIK it is an LDPA antenna since it catches may wavelengths, not a Yagi.
- The coax cable between the repeater and the antenna is too long. It was stacked vertically along the frame. Worse, it was originally coiled. I use folds instead to avoid loops, but I am not sure it has any impact on the direction (only noise/loss, which I admit was barely noticeable.)