The BIG and SMALL ANTENNA topic part 1


(Lollisoft) #82

I am thinking about a solar powered offgrid solution with a LoPy as a single channel gateway. Thus the lighting protection would simply be a pole (higher than the antenna) and that pole is mounted on my metal balcony guard railing.

Due to the WLAN connection to my network, there is also no connection to anything. That should be save enough. If anyhow the lighting hits the antenna, it should go to the pole and that is shorted to the balcony guard railing.

If I put the antenna below the railing, the railing it self is the highest point that gets hit first.

I think, that should work. A proper dimensioned solar module is another issue :slight_smile:
(I start with a 20W module and a 2500mAh LiPo)

And the SMA cable solution is a different option without an offgrid scenario.


#83

The most important part of lightning protection is grounding. Then comes grounding. And then comes grounding. Grounding however means: running a dedicated, large gauge (16mm² cross section and up) copper wire from the lightning protection to several grounding rods in the ground around your home. If you can't do this, forget about lightning protection altogether.

Why DC grounded antennas are no good for lightning protection, even though (mostly Chinese) manufacturers make that claim, is that they shunt the EM lightning energy away to the common ground, damaging or destroying everything that shares a connection to this ground. Your gateway for sure, maybe even your home appliances (through the earthing pin) or your router (thorough the ethernet cable). If they shunt altogether, because the DC grounding circuit is just a small resonant circuit that will never survive a lightning strike and possibly not even a nearby strike.

If you are unable to provide the large gauge dedicated grounding wire, then forget all about lightning protection. Any other measures will just give a false sense of safety.

But like @BoRRoZ says, you shouldn't lie awake from an unprotected LoRaWAN antenna either. In Europe you have on average 2 to 4 lightning strikes per km² per year. Most of them hit ground directly. The chance of one hitting your antenna is incredibly low, especially if there are other structures in the vicinity.

A completely off-grid gateway is the best lightning protection there is. Putting other poles in the vicinity and connecting them to other metal structures is a very bad idea and will negate the lightning safety of your off-grid solution. You should actually even increase the insulation between your gateway and your building, e.g. by putting it on a rubber mat. This will make your gateway 'invisible' for lightning.

In general, it is always a bad idea to put lightning rods in the vicinity of antennas. The near field effect will negatively affect the performance of the antenna.


(Lollisoft) #84

Ok, I just want to try these housings https://www.amazon.de/gp/product/B00BAADN4Y/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 to contain the circuits and only the antenna and the solar module should be connected to it.

This box will then placed on my balcony onto a desk and simply fixed with a cable tie. The antenna is then just at the height of the guard railing.

I hope that I get at least as much as doubled range. My tests from inside got to 700 meters only.

I can't install any antenna, as I need a permission to do so :frowning:


(Aanhanger) #85

Found some other cheap antennas on Alibaba, maybe we should start a buying group. If you order 5, they only cost 10 dollar a piece! (they don’t ship a single one even though the page says so, I contacted them).

I’m in if some others want to buy one for cheap :).


#86

very cheap indeed, but I think it's easier buying together within the same community / city, another possibility is that you contact the supplier again and ask him for a special TTN discount and that he can use this topic to promote his antenna for a special TTN user price :wink:


#87

If we do group ordering, than we'd better order decent antenna's from reliable brands. I have yet to see an Aliexpress/Alibaba antenna that actually has some gain at all, despite being advertised as one million dBi :stuck_out_tongue: .


#88



* The receiving GW is placed on the Rivium Quadrant @ 81 mtrs - tx is @ 18 mtr
"channel": 3,
"rssi": -123,
"snr": -2.8


#89

What was the SF and the output power?


#90

Interesting stack of RF connectors you have there :smile: .


#91

SF7BW125 - the output power.. hmmmm.. don't know exactly , I used the TTN 2483 lib, have to find out

I have some better results with this 3 dbi 'indoor' set up compared to the indoor GP :sunglasses:


(Jezd) #92

I took the cheap and untested route, don't judge :slight_smile:

http://www.ebay.co.uk/itm/868MHZ-915MHZ-GSM-3G-Sucker-Omnidirectional-High-gain-Antenna-7DBI-super-/201249960496?roken=cUgayN

(due in next 10 days)


#93

did you say 7 dbi... :wink:


#94

forgot this one … but working fine


#95

indoor antenna's close to double glazing, or in low energy buildings, can be a problem (losing 10-20 db)
there is not much info to find on the net .. so try it yourself.. place the indoor antenna a few meters away from the window :sunglasses:


(Jezd) #96

On quick run around with gateway on original RAK small antenna using a badger node I'm getting to around 1.25km :frowning: gateway indoors mind and behind thick walls/double glazing


#97

rainy stormy day in Holland :sunglasses:


left 3 db omni vs right 9-13 db (depends on seller) directional


#98

Hi BoRRoZ,

what is this analyzer ?

thanks !


#99

it's an RF explorer combi

I used it here just to see if a LoRa packet was transmitted because the node was not usb connected so no feedback :sunglasses:


#100

How_To_Hide_Antenna

how to hide :sunglasses:


(Gry Kyo) #101

We have several Cell Towers disguised as trees on Dublin’s orbital M50 motorway. A cactus would be more obvious than a naked tower in this place :rofl: