Think of a Grand Piano
RF antenna size is directly proportional to wavelength size for the simple reason that the antenna needs to create resonance for a selected frequency.
By way of analogy, look at how a grand piano or an organ creates low (frequency) notes: they use, respectively, longer strings or larger pipes.
Radio frequencies are similar. So 169 MHz’s relatively long wavelength means that effective antenna sizes need to be relatively big.
For example, a 2.4 GHz RF device can typically have its antenna integrated into the module. By comparison, a 169 MHz RF module has an external antenna approximately 10 cm long (when shortened into a helical).
Obviously, if your application requires small size equipment (i.e., including antennas), you’ll want to discuss with us the various options for achieving your wireless goals.
169 MHz’s Range: Worth the Bigger Antenna
169 MHz RF modules can be pretty compelling due to their long distance range, even in crowded urban environments.
Our Application Note AN021, entitled “RF Modules Range Calculations and Test,” shows you how to do your own wireless range calculations. It then follows up with two 169 MHz case studies, taking you through the RF range formulas and comparing the calculated results to actual transmission measurements for each application.
One RF range case study, using the Radiocrafts RC1700HP-MBUS4 Development Boards and 169 MHz antennas for a free line-of-sight (LoS) installation between two hills in Norway, demonstrated a wireless range of 8.3 km. In theory, with the calculated link margin of 32.6 dB, it could reach a distance roughly 32 times longer).
Low-Cost, 40 km2 Downtown RF Coverage
Another wireless range case study in AN021 tested Wireless M-Bus 169 MHz transmission in typical, “real-world” urban outdoor environments; in this case, downtown Oslo.
Actual urban RF range results are subject to great variation from location to location and environment to environment; but simple rooftop tests can help verify your range calculations.
In this case study, two standard, off-the-shelf antennas were installed on rooftops, connected to a standard Radiocrafts RC1701HP-MBUS4 169 MHz Development Kit and module. They successfully communicated at a wireless range of 3.5 km over downtown Oslo.
Using low-cost components to create a very basic 169 MHz star network, you could cover a circular range of 40 km2 in a similar downtown environment.
If you wish to design your own, application-specific RF tests, contact our Wireless M-Bus support engineers so we can help you make the tests as rigorous as possible.