the first one is good.
Range depends on both receiving and sending antennas. I have used the antenna design here with very good results, 3.7Km in urban area without Line of sight and an RFM95 module. The gateway had a home made collinear antenna with sections 5/8 - 5/8 - 1/2. I am not sure what the gain is and I don’t have the tools to measure it. On the same gateway antenna, I manage to get a 1.2Km link using this
@ferrero in the 12 or more months since your 868 and 915 colinear antenna designs were published I’ve built a few as trials. I can’t achieve a VSWR below 4:1 without adding ground plane radials, whereas your modelling shows the antenna being less than 2:1 at resonance. Also the dimensions of the 915 MHz version don’t seem to be scaled from the 868MHz version (ie dimensions reduced by the ratio of 868/915).
The concept of a light weight element inside a radome is just what some gateways need, but can’t replicate your work.
Wonder if you can shed some light on the dimensions and VSWR/ groundplane.
I experimented a bit with the antennas I have (20cm whip antenna, 37cm, homemade GPA), and I found something that my limited knowledge of radio is not adequate to deal with.
If I put the GPA directly over a node, with radials that go down partially around the node, performance (RSSI) is slightly worst than when I put the antenna more elevated, with about 20cm of H-155 cable (vertical). Do you think there is interference between the node electronics and the radials?
Furthermore, I noticed a small increase of performance if I put the GPA radials on the 20cm antenna (and more if using the same H-155 extension as above…).
I will try to confirm the experiment with another node and possibly with half-way elevation.
(gateway was at about 60m outdoors, almost line of sight but node indoors, in noisy environment)
Most antenna’s will not have a perfect 50 ohm match and therefor they will return a (smaller or bigger) part of the signal back. This signal will usually also travel on the outside of the feeding coax back to the node. This will make the coax (and the node) radiate and so they will become part of the antenna, disturbing your theoretical radiation pattern. (The pattern may radiate more upward or downwards, leaving less power in the desired horizontal plane)
So comparing different antenna’s with different coax cable lenghts is tricky.
If you want to prevent the feedline and/or node from radiating and disturbing the antenna radiation pattern you should put a ferrite clamp-on over the coax, as close as possible or at 1/2 lambda (17cm) from the feedpoint of the antenna.
Ferrite clamp-on filters are available in many sizes , so you can easy find a size that will exact fit your coax feedline while it’s position on the cable stays fixed.
The placement of a antenna has influence on the radiation pattern. Take a look at the simulations I made for the GPA antenna : Very simple homemade outdoor 868Mhz antenna (groundplane)
Thanks @costo, in this case I have a male to male SMA adapter in one case, and about 20cm of H-155 (with SMA connectors at both ends) in the other. Has ferrite to be isolated from the metal adapters?
Thanks @lex_ph2lb, I crossed your charts time ago (they made me put a single channel gateway just under the roof 
), and I also implemented the GPA following your instructions (with some deviation).
However, in this case there is not much difference in height: 20cm of coax, by the way I also compensated the height in order to have the antenna top more or less at the same height. And RSSI difference is about 5db (-55 vs -50), on 3 alternated sessions. I will have to try with a different node.
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I do not think it is nescessary to isolate the ferrite clamp electrically from the outher coax.
In most cases the use of several ferriteclamps in series will improve the RF-isolation.
Coincidentally I performed a similar exercise as jpmeijers original catalog, but for the 915MHz band. The apparent poor performance of off-the-shelf antennas caused quite a stir on LinkedIn.
Here are the version one results, with the antenna mounted on the VNA just like jpmejiers did. I believe that’s a good indication of performance in most typical configurations, where you screw the antenna directly to the electronics enclosure.
Here are the updated results with the antenna connected through 50cm of cable, mounted on some non-RF active material. I believe that’s a good indication of what happens if you take the ground plane away, as would be the case when you’re mounting the antenna externally.
Hmm, the previews aren’t very clear. Here’s some links to the originals: Antennas.pdf (2.0 MB) and Antennas with 50cm cable - smaller.pdf (398.0 KB).
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I’ve been using this antenna on AU-915 with good results. I’m about to start deploying a lot more gateways, and i’m wondering if i’m better off using osmethign lower gain.
14dBi? Phwoah. Probably a great option if you can also add an additional low gain antenna within the building for reception below the high gain antenna.
Im not sure if i belive that it really is 14dbi
Thanks - this is the serious version of my incidental finding
@dicktonyboy, early last year you were modelling antennas. I’d appreciate your advice if think the modelling software would be suitable for a Meandering Monopole, something like this one http://www.rroij.com/articles-images/IJAREEIE-1596-g002.html
Interesting antenna (maybe for a node): https://www.amazon.com/RFSPACE-Ultra-Wide-Band-Antenna/dp/B07NPRC1SR/
interesting yes, and it probably works on a node, but with an VSWR >1.8 @868 there are better (and cheaper ) choices imho.
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On the large size, maybe useful on the front end of a spectrum analyser.
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I would have thought an antenna on both a node and a gateways needs to be somewhat frequency selective to filter out unwanted signal and improve SNR. The antenna is the first filter in the receiver chain. A wideband antenna will pass un-necessary RF to the receiver thereby reducing SNR and performance. Seems OK for a spectrum analyser or a broad band receiver but can’t see a benefit for Lora based systems.
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Hi I’ve built a outdoor gateway using a IC880a and a raspy zero W. Im totally satisfied with the range but I didn’t use the whole potential because currently the Antenna of the gateway is located inside of the case.
Maybe someone made already good experiences with cheap outdoor antennas?