Core Electronics Forum

LoRaWAN Upgrade: Outdoor Antenna

Our LoRaWAN Gateway just got an upgrade: an outdoor antenna mounted nice and high. We've gone with a full wave antenna to get the most out of even the weakest of signals. Connecting the antenna to the Laird Sentrius RG191 LoRaWAN Gateway was straightforward; our antennas have a 5-meter low loss RF cable which is terminated with an RP-SMA connector. In short; they fit together without any fuss.

The Adamstown & Kotara area (where we're located) was in an RF shadow as it's surrounded by hills. The new outdoor antenna has more than doubled our contribution to the local LoRaWAN coverage, we had hits up to 6+KM away (which is impressive for an urban environment). 

After the antenna install I grabbed my trusty TTN Mapper and got to the streets for a drive. In the map below you can see the RF shadow I referred to - the whisps of blue that fly-in from the right and go right over the top of us. 

Our new setup caters for the entire Adamstown area, which is so refreshing to see!

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Hi Guys,
I am wanting to order one of these full wave antennas for my farm but am concerned about lightning strikes and resulting equipment damage… Have installed any lightning protection to the antenna / cable?

Thanks
Jon

Hi Jon.

Inline-lightning protection is a bit of a fallacy, a tiny air gap created by a fuse/device will not stop a lightning bolt that travelled 10Km and is unloading 100 million Joules of energy.

Lightning is always a risk, though not often elevated if the overall height of the house remains the same. Much like TV Antennas being installed, tyically on the side of the house (yet lower than the peak of the house). Sometimes they are higher, I’m no expert Antenna installer though.

There’s also a train of thought that the lightning risk-height of a house is the top of a triangle, where the bottom is the ground and the lines intersect with the top-side edges of the house. Ammeture radio enthusiasts often follow this approach, as you’ve undoubtedly seen at some stage. They’ll get their antennas right up to that point, not always with independant lightning protection in place (though I personally wouldn’t do it!)

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Graham,
Maybe Im being simple, but I think you are suggesting that as long as the top of the antenna is below the highest point of the house, the likelihood of the antenna being struck is much less, kind of like attached?

IGA_18_6_2019_11_32_59_169.pdf (30.7 KB)

On a similar line of thought, my house has a belt of tall trees close by on one side (fortunately the side I dont need to have huge LoRaWAN distances). I am assuming that these would also provide a high degree of lightning protection, especially if the antenna is below the house ridge.

R
Jon

That’s my take, consider how home TV antennas and the like are installed.

Anything taller than your house will likely provide a easier path for lightning. There are ways to impliment lightning protection with a higher-than-average rate of success, such as the below image I found on Google, though from what I understand it’s still lucky dip.

Not to scare you, because it’s just so unlikely, but consider photos you see on Facebook / social media of cars being hit by lightning (mind you, people almost always survive a car hit as the lightning goes around the chasis and into the ground). None the less, those pictures almost always show street poles, houses, trees, lots of other choices/paths for lightning. It’s just out right unlucky if it happens.

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There’s a lot of information on this topic and even an Australian Standard if you have about $350 spare (Australian Standard AS/NZS 1768-2007 “Lightning Protection”). The air gap or gas discharge protection on your antenna is the first stage protection to prevent the current from flowing through your equipment. You need a second stage MOV (metal-oxide-varistor) device to protect your equipment from the voltage spike. The Orca DX Club have a good presentation on it here:

Be careful with cheap protection. Most of the devices you buy in your local shops don’t react fast enough to stop the voltage spike before it does damage.

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Hi Graham,
Do you know how long your antenna extension cable was / is between the antenna and the gateway?

Thx
Jon