AMR Signal Propagation
Utility meter data signals, having been originally intended for reception from the street by a drive-by, vehicle-mounted receiver or from a stationary receiver mounted to the top of a streetlight pole, pose some reception challenges when the receiver is located inside the building to which the transmitting meter is attached. However, these challenges need not be obstacles.
In the 900 MHz radio frequency range, the frequency band in which many utility data transmitters operate, radio waves will travel easily through low-density construction, like the wood-framed walls and floors of many American houses. The signals even travel fairly well through denser materials like concrete and brick. The real obstacle is metal, and, unfortunately, many electric utility meters are separated from the house they serve by a metal cabinet.
Despite metal obstacles, radio signals benefit from two rather useful behavioral characteristics:
- they can bounce off objects, and
- when passing through or around objects.
So, even when a metal barrier (like a steel meter cabinet) completely blocks the direct signal path between transmitter and receiver, chances are that a reflection of the signal will get through anyway. The reflected/refracted signals will not be as strong as a direct signal, so they will not travel very far. But in most homes, they will travel far enough to reach your computer.
If you have problems picking up your meter signals from your computer, try changing the orientation of your receiver’s antenna. If you are using a short antenna, try using a full-size dipole antenna instead. Also remember that your computer’s metal case can itself block or reflect signals.
Also remember that signals can bounce off almost anything – a neighbor’s house, a car, a tree, a deck railing. If you can move your computer around a bit within the house, you will find that certain locations provide far better reception than others.
The diagram above shows how this works with a wall mount electric meter. Water and gas meters behave similarly, but tend not be as temperamental due to not being mounted in a metal box facing away from the house.