Thank you @TijnOnlijn for your LABS story about adding an outside antenna to an indoor gateway.
Let’s discuss the story in this topic, there are enough antenna experts (@lex_ph2lb, @jvgenderen?) in our community to provide feedback to optimize the story (if necessary).
Topic looks good.
At first glance some minor note :
The antenna I use is a GP901 ground plane antenna. (http://www.sirioantenne.it/ru/cellular-base-ru/gp-901-cgp-900-c/). It has a gain of 5 – 8.15dBi. This is too high, since you’re only allowed to use 2.15dBm for sending.
The Dutch license free radio frequency allocation states :
865,000 - 868,600 MHz 25 mW e.r.p. - < 1,0 %3
Ref from Table 1 at : https://www.agentschaptelecom.nl/sites/default/files/brochure-vergunningsvrije-radiotoepassingen.pdf
25 mW erp is the emitted power with a 2.15dBi aka 0dBd antenna (dBi = dBd + 2.15 & dBd = dBi - 2.15 ). And 25 mW erp is 14dBm (to be exact 13.979 dBm). I think the 2.15dBm schould be changed into 14dBm.
This value can be used to calculate the optimal (and maximum) GW dBm. You start with 14 dBm, substract the antenna gain in dBd or when you have a antenna with dBi gain specs use the dBi and add 2.15 dBi, and finaly substract the cable losses of it.
For a antenna with gain specified in dBd use :
GW dBm = 14 dBm - antenne dBd - cable loss in dB
For a antenna with gain specified in dBi use :
GW dBm = 14 dBm - antenna dBi + 2.15 dBi - cable loss in dB
For example when a 8dBi antenna is used with coaxial cable with a loss of 1dB cable (loss = negative gain so so -1dB)
GW dBm = 14 dBm - 8 dBi + 2.15 dBi - -1 dB = 9.15dBm
Hi .
already mentioned in the lbs/story there are a few step to follow to increase you lorawan coverage .
#1 Antenna & coax(feeder)
Depending on your budget and antenna building skills there are 3 options …
-Build you own antenna:
pros => fun, educate yourself on antenna theory.
cons => specialized equipment needed to test if the antenna is build properly and is swr (standing wave ratio) is correct:
-The china option
pros => mostly cheap.
cons => you never know if your antenna is any good . poor build quality.
-the pro option:
pros: There are a number of professional antennas builders on the market.
Procom, kathrein.
for example the procom antenna ; http://procom.dk/products/531-cxl-900-3lw-nb868-mhz
is in my opinion a perfect antenne for a gateway or even a stationaire node.
these antennas are simply good and excellent for gateway site on high buildings and hars and windy environments. and the important radiations patterns.
cons : not cheap ! .
[quote=“jvgenderen, post:3, topic:4243, full:true”]
for example the procom antenna ; http://procom.dk/products/531-cxl-900-3lw-nb868-mhz
is in my opinion a perfect antenne for a gateway or even a stationaire node.[/quote]
This seems to be a vertically polarised antenna with maximum gain in the horizontal plane. Is this really the best option for a gateway? If you place a gateway on a building, I would suspect you also want reception in that building or close by it, right?
can I summarize this to the fact that I made a typo and should change the dBm to dBi?
Just to understand the different categories; what is the price range for the third category?
indeed a very good one !
in fact, it had the best VSWR (1.29) from all the cheap antenna’s I’ve tested.
does anyone have personal experience with this conrad thing? ttnmapper results perhaps? I saw the thing before bug I find it hard to judge if it’s cheap and great or cheap and trash.
You are correct. I have misread :
The antenna I use is a GP901 ground plane antenna. (http://www.sirioantenne.it/ru/cellular-base-ru/gp-901-cgp-900-c/1). It has a gain of 5 – 8.15dBi. This is too high, since you’re only allowed to use 2.15dBm for sending.
I read it like : when using this antenna you would transmit to much dBm.
It indeed should say : 2.15 dBi.
My additional comment is additional information for power output calculations. .
Regarding the commercial conrad groundplane antenna, I got 2 of them and they laying on my workbench for testing.
will this also work for 915 mhz? sorry zero antenna knowledge here.
Hi epyon.
the antenna is vertical polarized and omni directional …
that means that the antenne emits it energy verticaly in all directions (H-Plane) and E-plane emits a small lobe downwards and the most of it energy towards the horizon.
if you place the antenna on a hi rise building >20 floors the most of the top floors are covered but the effect of concrete and coated glass ar taking effect and the basement has no signal left …
but for indoor lora solutions commonly the don’t use these type of antennas …
the “problem” antenna types is that the radiate in a slight upward angle and when placed on a high building the signal is beamed towards heaven 
therefore the radiation diagram is more important than the gain of the antenna.
In my working life and as a indoor gsm design engineer we used small panel antennas
or a mexican head antenna
these antennas where painted in the colour of the surrounding and placed on wall or sealing. .
/Joost
that is a typical 1/4wave antenna. it has no gain …
any gain stated stated as dBi is the gain seen from an isotropic antenna.
this the nog existing antenna and simply does not exist.
These values (dbi) give you a 2.15 dB more gain . but is real live this is the 0dB antenna …
the value that is normaly is more acurate is the dBd (the gain as seen from a dipole antenna).
if the vswr is below 1: 1.5 the antenna is good …
When taking a closer look at he vswr diagram this antenna is absolute no good for 868 lora.
a vswr above 1:1.5 is bad …
is is a GSM antenna as i have seen …
for 915 it is beter suited … the vswr is good …
/Joost .
I have used both the Conrad Aurel GP 868 and the Sirio GP901, both offer good value for money. However with the Sirio GP901 you definitely have a wider range which is to be expected because of its higher gain in the vertical plane. As mentioned before: because you will need to trim down gateway output power (assuming the cable loss is less than the antenna gain - 2.15 dBi) your gateway might not be able to reach a node that it can receive. This would hamper downlink messages or prevent OTAA. However for ABP nodes without downlink requirements you will definitely have a better reach. I have ttnmapped both antenna quite intensively, but because I replaced the Conrad with the Sirio the results can not be compared on the map. I would have to recreate a coverage map for the different periods.
The reach with the GP901 is roughly 8 km with incidental reception up to 20 km (rural area). With he Conrad Aurel I never saw more than 3km. These figures are with the antenna still inside (on the attic), so far from ideal.
For anyone interested in what others are doing out there it seems Sigfox also uses the Procom antenna on their gateways. Similar to the one suggested by @Epyon
To make clear …
the max ERP (effective radiated Power) is 25mWatt and not EIRP !!! (effective isotropic radiated Power)
to simplify … a transmitter with a dipole antenna (0dB gain) and 25mwatt(14dBm) is oke …
but there is to much focus on the max transmit power …
invest in a good antenna and good gateway site… don’t worry about 1 or 2 or even 3dB to much power …
and forget the dBi it is a gain seen from an antenna that does not excist …
dBd is more realistic …
the dBi term is mostly used as it look nice that your antenna has more gain … marketing tricks …
/Joost …
Next topic
#lighting protecting …
1st lighting protecting does not exist !!!
The most important thing about lightning protection is to keep the shit outside …
make sure that you mast is properly grounded …
if this is at home … DO NOT connect it to your inhouse electrical installation…
if you use a pole to side of you house make sure that there is a copper al aluminium wire with sufficient thickness (16-25mm2) to a grounding rod in the ground …
if the lightning strikes it follows the path of less resistance … and hopefully into the groud …
oke . .that is step one …
next step is to use shielded cables to all outside components …
-coax is already shielded … check.
-use stp (shielded utp) and propely connect the correct rj45 connector … there is a small shield and ground within the cable that should make contact with the grounding of the utp chassis …
-if you place a gateway or even a node in a metal box outside . connect a grounding cable to the chassis and make sure that makes contact with bare metal. and connect the cable to the grounding rod .
these greatly reduces the amount of energy getting into your building when a strike hits …
you may still have equipment being broken bij the emp (Electromagnetic pulse) or leftover energy but it wil keep most of the strike outside.
if you place all this on a building with a copper/alu grounding system on its roof … connect all grounding wires to that system with proper clamps .
this a hamradio repeater site in the south off holland on a corporate building …
most of the building owner not only advise you to do this but the will order you to do so …
It is not a matter of you lossing a 500$ or euro gateway . but if the energy hits the ICT infrastructure of a big company with a big legal department … you do not want to be blamed for causing this …
In Holland there is a way to pay for a “consequential damage” insurance that covers the most of you problems if the may happen …
/Joost .
If you’re connecting to the ICT dept of a big company maybe the best option is to use optical fiber no? It’s not even that expensive these days.
Then use a surge protected AC outlet for power.
You are right …
but there is power needed to the gateway … and i am sure this does not work over fiber
a surge protector does not prevent any jumping of lighting … advise keep the shit outside and ground properly .
/Joost
