In the air, v is equal to c, the speed of light, which is 299.792.458 m/s. The wavelength of a frequency can be calculated by the formula v / f, where v is the speed of the transmission and f is the (average) transmission frequency. The simplest antenna can be made just from a single-stranded 22SWG wire. So with the above comparison, I think we can all agree that the RFM69 module is far better than the ASK Hybrid Transmitter and a receiver module.Ĭaution! Attaching an antenna to the module is mandatory because without it the module can be damaged by its own reflected power.Ĭreating an antenna is not as hard as it may sound. Now, I set everything to zero and the distance to 9KM Frequency to 433MHz and We get a horizontal received-power of 104.3 dBm First, let’s assume that we have a line of sight connection between sender and the receiver and everything is perfect as we know our Budget for RFM69HCW is 140 dB so let’s check the biggest theoretical distance we can communicate, we set everything to zero and the distance to 500KM, Frequency to 433MHz and we get a horizontal received-power of 139.2 dBm According to the datasheet of the RFM69HCW, it has a link budget of 140 dB compared to 105 dB of the ASK Hybrid Transmitter but what does this means is this an important difference? Fortunately, we find Radio Link Budget Calculators online so Let's do some calculations to understand the topic better. The link budget is deducted by all sorts of obstacles and noise between the sender and the receiver like distance cables walls trees buildings if the link budget is used up, the receiver only creates some noise at the output and we will not get any usable signal. The link budget also has to do with a link or the connection between the sender and the receiver, it is filled up by the transmission power of the sender and the sensitivity of the receiver and it is calculated in decibels or dB it is also frequency-dependent. So, what is this link budget and why it is so important? The link budget is like every other budget, something you have at the beginning and which you spend over time if your budget is used up you cannot spend more. To understand the range better we have to deal with quite a complicated topic called the RF Link Budget. Note: Because of its comparatively low power and short-range, implementation of this module in a small project is not going to be an issue, but if you are thinking about making a product out of it be sure you are using the correct frequency for your location. All major RF communication parameters are programmable and most of them can be dynamically set, also the RFM69HCW offers the unique advantage of programmable narrow-band and wide-band communication modes. Different frequencies are legal in different areas so that’s why the module has many different versions 315,433,868 and 915MHz. The RFM69HCW is devised to work in the ISM (Industry, Scientific and Medical) band, a set of unlicensed radio frequencies for low-power, short-range devices.
0 Comments
Leave a Reply. |