LoRA measuring antenna's - going outdoor
This page was last updated : 11-Mar-20 23:09:21
Going outdoor
As I wrote, the best way to test antenna's is out in the field. And after a few days of rain we did. My lovely XYL Eva took her camera with her so she could made a few pictures.
The setup is like this. I placed the server in a plastic box with a white PVC tube on top of it. On that tube I placed the groundplane antenna. The complete assembly I put on a photo tripod in the field on a distance of 25m from the client. The client antenna (the antenna under test) I placed on another photo tripod.
Well you get the point when you see the picture below.
A close-up from the client groundplane setup.
Then it was time to fire up the first test. Both antenna's are groundplanes to get a baseline.
The results from this test are shown below.
Groundplane 2 groundplane (Baseline) 25m ----------------------------------------------------- SENDRSSI|RECVRSSI -39|-38 -42|-38 -42|-38 -42|-38 -42|-37 -42|-38 -42|-37 -42|-38 -42|-38 -42|-38 AVGSENDRSSI|AVGRECVRSSI -41|-37
Then it was time to hook up the original Colinair
And getting very disappointed results.
Collinear org 2 groundplane (25m) (no tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -52|-48 -51|-48 -51|-48 -51|-48 -51|-48 -50|-46 -51|-48 -51|-48 -52|-48 -52|-48 AVGSENDRSSI|AVGRECVRSSI -51|-47
Almost -10 RSSI against the groundplane, thats a major downer. But knowing that the radiation angle of these antenna's (Omni Directional HIGH GAIN Dipole : link) is quite different from groundplane antennes, I decided to tilt the antenna 5 dgr.
Collinear org 2 groundplane (25m) (5 dgr tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -42|-41 -45|-40 -45|-41 -45|-41 -45|-41 -45|-41 -45|-41 -45|-42 -45|-42 -45|-42 AVGSENDRSSI|AVGRECVRSSI -44|-41
Well its better but still -4 RSSI against the groundplane. Time to used the updated Coliniar antenna (with the top loop).
Collinear updated 2 groundplane (25m) (no tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -43|-42 -46|-42 -46|-43 -46|-43 -47|-43 -47|-43 -47|-43 -46|-43 -46|-43 -46|-43 AVGSENDRSSI|AVGRECVRSSI -46|-42
Standing up, its better then the original one, but still -5 RSSI against the groundplane. Time to tilt this puppy.
Collinear updated 2 groundplane (25m) (5 dgr tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -46|-42 -43|-41 -45|-41 -45|-42 -45|-42 -45|-42 -45|-41 -45|-42 -46|-42 -45|-42 AVGSENDRSSI|AVGRECVRSSI -45|-41
Well its better but still -4 RSSI against the groundplane. But it seems that the upgrade model has a different radiating pattern. That's a thing to investigate. But having only 1.5m coax cable in the measurement setup it may have not enough ground to press again. So adding 1 piece of wire to it (at home I'm using a aluminium tube where I mount the antenna on).
Collinear updated extra ground 2 groundplane (25m) (5 dgr tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -43|-39 -45|-41 -44|-39 -45|-41 -45|-41 -45|-41 -45|-41 -45|-41 -45|-41 -45|-41 AVGSENDRSSI|AVGRECVRSSI -44|-40
And +1 RSSI. We are getting there. But I didn't have enough wire or tubing with me in the field to continue this direction.
Next antenna to test is the J-pole antenna.
J-pole 2 groundplane (25m) (no tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -41|-39 -43|-39 -43|-38 -43|-39 -43|-39 -43|-39 -43|-38 -43|-39 -43|-38 -43|-39 AVGSENDRSSI|AVGRECVRSSI -42|-38
Almost as good as the groundplane by default, so lets see if a little tilt is making it better.
J-pole 2 groundplane (25m) (5 dgr tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -41|-41 -45|-41 -45|-41 -45|-41 -45|-41 -45|-41 -45|-41 -44|-40 -44|-40 -44|-40 AVGSENDRSSI|AVGRECVRSSI -44|-40
No it isn't. But by default a nice antenna design it seems.
Now it's time to test some other antenna's which are out of the box (no DIY). The result tell there story.
Original LORANK8 2 groundplane (25m) (no tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -42|-38 -43|-38 -43|-38 -42|-38 -42|-38 -43|-38 -43|-38 -43|-38 -43|-38 -42|-38 AVGSENDRSSI|AVGRECVRSSI -42|-38
Another non DIY antenna which I had laying around.
China magneet voet 2 groundplane (25m) (no tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -52|-49 -51|-50 -52|-49 -52|-49 -52|-49 -52|-48 -52|-49 -52|-49 -52|-49 -52|-48 AVGSENDRSSI|AVGRECVRSSI -51|-48
Probably it needs a large metal groundplane (like a car roof) to work good.
For another test I have increased the distance between the server and the client to 50m. I would expect a decrease of -6 RSSI because double the distance between a transmitter and a reciever and you get -6dB aditional path loss ( 59.13dB - 65.19dB ). You can check it out by using the Online Path Loss calculator (enter 25m, 868Mhz, no gain and enter 50m for the same freq and gain).
Want to know more about this ? Check out this TTN video.
groundplane 2 groundplane 50m ----------------------------------------------------- SENDRSSI|RECVRSSI -45|-45 -49|-44 -49|-45 -49|-45 -49|-43 -46|-44 -49|-45 -49|-44 -49|-45 -47|-44 AVGSENDRSSI|AVGRECVRSSI -48|-44
Well that didn't come like a supprice. I love it when expectations are coming true :-)
With this new distance I wanted to test the updated Collinear again and it seems that the radiating pattern indeed has his influence. Almost the same result as the groundplane antenna.
Collinear updated 2 groundplane 50m (no tilt) ----------------------------------------------------- SENDRSSI|RECVRSSI -49|-45 -49|-45 -50|-46 -49|-45 -48|-44 -49|-44 -49|-46 -49|-45 -48|-45 -49|-45 AVGSENDRSSI|AVGRECVRSSI -48|-45
I wanted to put the server on 100m distance and do some more tests but the Dutch weather had other plans (quit a good rain shower). :-( But for now I happy with the results. Got some sun shine and results to process.
My expectations are that the Collinear antenna will work and show more gain over a longer distance. These antenna's are designed for long distance and have a flat radiation angle (link). This spotlight behavior make them less usable when the antenna is on a high location and the node is near underneath that spotlight. So when you have a gateway and want a outdoor on a high location and you want to pickup close by nodes, a Groundplane is the best choice.
But the best choice is to experiment with it and try to find the antenna for you're needs.
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