I don't seem to be getting the range advetised! Is my module broken?
Your module is probably not broken. Radio range is dependant on a lot of things and all must be attended to to make sure you get the best performance!
- Tuned antenna for your frequency - getting a well tuned antenna is incredibly important. Your antenna must be tuned for the exact frequency you are using
- Matching frequency - make sure all modules are on the same exact frequency
- Matching settings - all radios must have the same settings so they can communicate
- Directional vs non-directional antennas - for the best range, directional antennas like Yagi will direct your energy in one path instead of all around
- Good power supply - a nice steady power supply will keep your transmissions clean and strong
- Max power settings on the radios - they can be set for higher/lower power! Don't forget to set them to max.
- Line of sight - No obstructions, walls, trees, towers, buildings, mountains, etc can be in the way of your radio path. Likewise, outdoors is way better than indoors because its very hard to bounce radio paths around a building
- Radio transmission speed - trying to transmit more data faster will be hard. Go for small packets, with lots of retransmissions. Lowering the baud rate on the radio (see the libraries for how to do this) will give you better reliability
How do I pick/design the right antenna?
Various antennas will cost diferent amounts and give you different directional gain. In general, spending a lot on a large fixed antenna can give you better power transfer if the antenna is well tuned. For most simple uses, a wire works pretty well
The ARRL antena book is recommended if you want to learn how to do the modeling and analysis
But nothing beats actual tests in your environment!