For a larger project where I basically want to boost phone signals indoors using an external antenna I have devised a small experiment to make sure I get the basics right before I expend a lot of energy.
Basically, I have made an enclosure to reduce signal strength in which I put a cell phone displaying the current RSSI or dBm and a small-scale version of the external and internal antenna setup. Basically just two small antennas connected by a wire.
The idea was that I should be able to measure a difference in signal strength inside of the box when putting a small antenna connected to another antenna outside of the box. This would then validate the feasability of using the bigger antennas.
Step 1 was to make an enclosure that would block (some) signals. A card board box wrapped in aluminium foil was no true Faraday cage, but when closing the lid it managed to reduce the signal strength by 15dB, which is noticable.
Step 2 was then to verify that these antennas would boost the signal inside of the box. This is where I fail, somehow. While closing the lid of the box made the signal go from -90 to -105 on the dBm scale, putting the antenna in there made absolutely no difference - no matter how long I waited.
I suddenly realized that I might be reading the wrong figures, as I still had 4G enabled (the antennas are both for about 900 MHz, while 4G is 1800 and 2100 MHz in Norway), but disabling 4G and strictly running on 2G made no real difference.
So this leaves me wondering: what am I doing wrong? Are there some basic assumptions I have made on how this should work that are just plain wrong?
- I have verified that there's no short in any of the links from the black whip up until the N-connector using a voltmeter (0.6 V reading).
- I have turned off 4G
- I have verified that I lose 12-15dB of signal when closing the lid
- Tech specs on the long whip (900 MHz range)
- Tech specs on the stick antenna (900 MHz range)
- The splitter box used to connect the two male cable connectors seems to be fine too when checking using a voltmeter.