we are using a Comtac Modbus Bridge. As you can see, it has an external antenna.
I was wondering if it makes any difference if we lay the device on some board (antenna horizontal) or mount it to a wall (antenna vertical)? All the Gateway antennas are mounted vertically.
I tried to do some research on that topic but found very little useful about it. My radio knowledge is too limited (yet, of course, working on it ) to really figure it myself. Does someone have some information or experiences regarding this?
Thanks & best regards
To learn more about this topic search for “Antenna Polarisation” where you will find to obtain the lowest path loss the two antennas should have the same polarisation. (read that to mean the same orientation).
You will find the loss between the transmit and receive antenna will have the function of the cosine of the angle between the two. So if one is vertical and the other is horizontal the angle is 90 degrees and the receive signal should be zero. Now, you will find there is some receive signal but this is coming from reflections and since this another topic to learn about I won’t go any further.
Simple rule: Since LoraWan gateways have a vertical antenna then its best if the node has the same.
thanks a lot for your answer. So the answer regarding devices with internal antennas is pretty simple: keep them vertical as your gateway antenna will be, too.
However, how about devices with internal antennas, e.g. Elsys CO2 sensor? Do they usually also have a dipole antenna where alignment with the gateway antenna matters or do they have a different antenna type where this does not matter? I currently have my CO2 sensor mounted vertically, whereas the device seems to be designed to be placed horizontally, e.g. laying on a table.
Thanks & best regards
You would need to check the preffered orientation for each device, there is no ‘standard’ that I am aware of.
All practical antennas are going to be orientation sensistive to a degree.
Thanks again. Looking at another end device, another question came to my mind:
With an external antenna, does it matter if the antenna is vertical but upside down?
Have a look at the following device. As it will be typically mounted on a wall, there is no way to get the antenna in an upright position without a cable. But getting the antenna in a vertical position by having it pointing downwards would be pretty easy, it seems the antenna can be straight or 90° tilted. What do you think? Is that ok or a bad idea?
Most antennas for vertical orientation when used pointing upwards will have a radiation pattern that is raised a few degrees upwards, exactly how much depends on the antenna itself and the effectiness of what its connected to as a ground plane.
So whether you get the same reception, in the example above, with the antenna pointing downwards, versus on a cable and pointing upwards, you cannot be sure, you would need to test it.