Using high-gain YAGI (11-23dBi) antennas for LoRa gateway (DON’T!)

Dear TTN-fellows,

I’m aware of the TTN fair use policy and the ISM regulations in europe that only allow 14dBm (or 25mW) :). For a particular project, I’d like to extend the range towards a specific direction. I have thought about using 11 or 23 dBi YAGI antennas that can be sourced from digikey:

https://www.digikey.de/products/de/rf-if-and-rfid/rf-antennas/875?k=yagi&k=&pkeyword=yagi&sv=0&pv1851=291672&pv1851=299188&sf=0&FV=-8|875%2C1850|417331%2C1850|417333&quantity=&ColumnSort=0&page=1&pageSize=25

Does someone have experience with those antennas? I’d like to use them on the gateway just to listen. I’d love to have one 2.1dBi antenna for receive and transmit connected and one 11dBi (or even the 23dBi one though i think that’s an overkill) to receive signals from a specific direction.

Can it work to feed the signal of two different antennas to one HF port like an SMA connector? Are there strategies to avoid that the high-gain antennas sends? If not, I would just lower the transmit power of the gateway.

I have also read the antenna part I and II but I think long-range YAGI antennas are not covered there.

Thank you!

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I’ve seen that Kerlink, the premium manufacturer of LoRa-Gateways, launched a new product:

You can connect two 868MHz antennas, one with 3dBi and one with 6dBi.

So how do you propose to modify the Gateway so that it only transmits through the legally compliant antenna ?

Do you have enough experience to set up the neccessry antenna switching and matching etc ?

Lowering the transmit power of the Gateway, so you dont exceed 14dBm through the gain antenna, would mean that a lot of nodes would not be able to receive messages or join.

There are good reasons why high gain antennas are not used, there is no point, if the gateway is to remain fully useable by all nodes.

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Of course you cant connect it. Just make sure that you don’t change the TX settings as it could damage your board.

Pycom example code uses 14dB as default but you can modify it to use less. The G3 band can use 20dB as it allows for 10% duty cycle.

Ping me at johnatgasxdotcodotuk and I can share some of the code I have run so that you don’t have people accusing you of abusing the band.

I have a YAGI on an iMST gateway in my back garden, it does great.

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So there is a configuration mechanism that allows a TTN compliant Gateway to operate at 10% duty cycle and 20dBm output within the UK ?

Hey, mechanism?

https://www.thethingsnetwork.org/docs/lorawan/duty-cycle.html

Follow that through to ETSI, you’ll see what we mean.

Just because the antenna can go to 23dB it can’t go that high unless the user manually sets the TX THEREFORE breaching the duty cycle.

I will soon be starting to experiment with G3 for emergency beacons

Is that still LoRaWAN? And TTN compatible? Because you can’t tell the backend what response slot to use and only the RX2 slot uses the G3 band where 20dB and 10% are applicable.
And nodes in the LoRaWAN standard are limited to the uplink frequencies which are in G1 so just 14dB and 1%.

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I am able to read IR2030, which is the actual regulation in the UK, which does follow the ETSI standard. I do understand the concept of duty cycle and its legal implications.

However, this is TTN and there is a requirement for nodes to stay within the fair access limits.

For readers who do not appreciate the full implications for nodes, just forget the legal duty cycle limits, the fair access limitations restrict you to a duty cycle of 0.000347%, which is far less air time than 10% or even 1%.

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Of course. The 30 second limit will severely prohibit that.

I am of course referring to private LoRa, my distinction was not clear.

Hi Jac. I am of course referring to private LoRa including TTI.

Page 13 might be of interest https://lora-alliance.org/sites/default/files/2018-04/what-is-lorawan.pdf

Enjoy.

The range is not only limited by the gain of your antenna but by the Line of Sight and the Fresnel Zone. One important thing that is sometimes forgotten is the fact that the earth is round. With the frequencies we use (abt. 868 MHz) you have a quasi optical propagation. That means your antenna needs to “see” the node or reflections of its signal.
To give you an example: with a TX-high of 60m the Radio Horizon is 32 km. If the node is 1m high your Line of Sight is 36 km.
What distance do you want to cover?
BTW: I would like to see a Yagi-Antenna with 23dBi gain, this would be a really big gun.

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If you don’t mind I use the standard, not the marketing glossy. TTN and TTI do not use G3 for uplink so no ‘emergency beacon’ is allowed to use the higher dB setting if it is a node. Only gateways can use it for downlink (the EU RX2 frequency is in G3).

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BTW, private and public LoRaWAN share the same rdio spectrum. So private implementations pushing the limits will render LoRaWAN unusable for everyone at that location. There have been reports (on this forum) from users that this already happened in some cities so beware you are not fouling your own nest.

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The frequency alone does not dictate local RX / TX performance, it is why we have LBT and ADR.

Thanks for your input, look after your nest.

Cool. I am sure that the LoRa Alliance guys will be happy to review your technical standards document.

No need, it is their document.

Haha awesome. Made me laugh out loud.

Hi Guys,
Thanks for your participation. I see that there is quite some vivid discussion going on :)!
To my knowledge, multiple antennas could be used with power dividers including wilkinson dividers:

That add 3dB loss due to splitting and on top 0.25-3dB insertion loss. One gateway has a relatively bad coverage towards a direction of nodes that are placed in a forest. Without the trees, there would be a line of sight. With a YAGI-antenna I hope to increase the range.
Can you recommend solutions to comply with the regulation?
Thank you!

Your missing the point here.

The gain antenna would allow the Gateway to receive signals from nodes that are further away. However the use of the gain antenna means you need to reduce the Gateway transmit power to stay legal.

So now the remote nodes wont be able to receive messages from the Gateway, get it ?

I get the point :slight_smile: