I ordered this module looking at the datasheet that it has a range of 2000m LOS distance. But now when I test it, I can receive signal from a maximum of 50m distance! It sends 2.4GHz signals. As far I understand, LOS distance means straight line distance. Am I making any wrong assumption about the datasheet?
Distance confusion about Shuncom SZ05-ADV ZigBee module
distancesignalwifiwirelesszigbee
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The simple answer is yes, as long as they use the same frequency range and bitrate, as there are multiple options for these in the standard. This means physical layer interoperability (i.e. if you wrote the code for one or both, the modules should be able to talk to each other), not application-layer interoperability (i.e. any two random devices with a Zigbee logo on the box will not necessarily have anything meaningful to say to each other :)
WiFi Signal Boosting
- The two devices should be in each other’s range.
- There's no such thing as "receiving range".
- Even if you boost one device's transition range while the other device is moving further, you should also do the same boosting (more power gain) for the moving device.
Your premises are partially correct.
An aside - Antenna gain:
The following is liable to confuse more than help. Just accepting "antenna gain" as a focusing of signals as wit a magnifying glass, will suffuce for this dicussion.
When I say below "increase antenna gain" I mean as far as the transmission between the two stations is concerned. Antenna "gain" is always only achieved by dealing with signals from a relatively smaller area. You can get an inefficient antenna, which clouds the issue, and antennae may reflect a radiation image in the ground plane, but for practical purposes antenna "gain" is identical to what you get with a magnifying glass. On the receive side, signal from a wider area may be captured but what is effectively being done is to acquire signal from a larger solid angle.
If you increase antenna gain of B relative to A then you will increase apparent transmitter power of B. But, using the same antenna you will also increase the apparent transmitter power of A as B will have the signal from a wider area "focused" by the receiver. So, increasing antenna gain increases range due to apparent boosting of transmit power by both stations.
If you increase the transmit power of B you will increase the B to A transmit distance but the A to B distance will not be affected. To provide an equivalent receive boost you need to reduce the receiver noise level of B proportionately. This is usually best achieved by use of a lower noise device in the receiver front end. This area involves the blackest of magic. It is usually easier to increase transmit at power at both ends than to increase receive gain and transmit power at one end only.
In a typical WiFi scenario the central station / master / access point / whatever, is shared amongst multiple channels and is able to bear a greater capital cost. By adding a booster that both increases transmit power and also adds a low noise receive amplifier you benefit all channels and remote devices concerned.
At least potentially, a unit which does not improve receiver performance and which increases transmit-power-only at the access point could support a greater outgoing data rate and slower incoming rate at lower power / signal to noise / worse BER. This would be useful for download dominant data streams which are what is commonly encountered. Whether the system used supports such split data rate configurations is protocol dependent.
Best Answer
Adding to what Connor Wolf said in the comments, transmitters have a defined maximum transmit power (usually measured in dBm or mW) whilst receivers have a defined maximum sensitivity. Together, plus several other factors, they form what is known as a "link budget". For instance, if you've got a 20 dBm transmitter and a receiver with a -60 dBm sensitivity, you can theoretically afford up to 80 dB in attenuation. Attenuation comes from many sources (connectors, cables, antenna matching, etc.), and the transmission medium as well (i.e., the air). They all might add quite a bit of attenuation. The data rate and modulation add to the equation as well.
After all that, if the antenna is perfectly omnidirectional (i.e., it irradiates in all directions like a sphere), the signal power will be distributed in all directions as well, diminishing its power rapidly in proportion to distance and other factors. If your antenna is not omnidirectional, however, it may "concentrate" the irradiated power in a cone shape, for instance, where all the power that would otherwise have been transmitted in directions you don't need is directed to the direction the antenna is pointed to instead. In this way, without changing the transmitting power you can reach farther, at the expense of not reaching every direction. The most extreme case would be a very very directional antenna, where you can transmit almost all the power in one specific direction. This is a very delicate setup and you need to point the antenna very precisely, because a little deviation from the line of sight (a small wind, perhaps) might mean lossing your target entirely.
Antenna directionality is usually specified in "dBi", which is how it varies from the point of view of an ideal dipole antenna, which has a known gain shape. An 8 dBi figure tells you that a receiver aligned with the most gain direction of the transmitter would receive 8 dB more of signal than it would receive if you have used a dipole. Not much. Mind that a receiver NOT aligned with the most gain direction would receive far less signal than it would from a dipole. That's how antenna directionality works: it takes from one direction in order to give to another.
The receiver antenna works in the exact same way, but backwards: if it's directional it concentrates its sensitivity in one direction, but becomes "deaf" to the rest.
Long story short, most RF modules specify the line of sight capability of the module with the most expensive and very carefully set up antenna, in a very specific situation which not adheres to your specific scenario. Some of them might include application notes specifying how, where and when the measurements where taken (things like weather affect the transmission too!). You might be inclined to think that this is a rip-off, but consider this: they don't know anything about your usage case; they couldn't specify what would be your results. There is no "common" scenario per-se: reflections (as buildings, objects, etc.) greatly affect the results. So, the most "honest" value (although I concede, misleading) is perhaps an ideal line of sight value.
Look at this link budget calculator for an idea of what is involved in the calculation.