You can also lose signal if you have too much metal of a similar length to your antennae nearby. I have 2 smart meters and if they are too close to each other they both lose the signal as they each contain a metal antennae of the same length. This is down to the way electric fields work and if nearby bits of metal are of a similar size to your antennae (the aerial within the mobile phone for example) the fields get distorted.
This effect is exploited in high gain TV aerials where there are directors which are the slightly shorter bits of metal than the dipole (the bit where the cable actually connects) precisely spaced on the side nearest the transmitter and reflectors which are the slightly longer bits of metal precisely spaced on the side away from the transmitter. These alter the electric field to focus the signal into the dipole. How well they do this is the aerial gain which is shown in dB. Have a look at a TV aerial to see how it is assembled and look at the adverts as to how much gain they have (which might be linked to the number of directors and reflectors they have).
So it is worth considering any metal that is near to the antennae of whatever piece of equipment you are using (particularly short lengths near the half wavelength of the frequency you're using).
