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warenbe
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Joined: Fri May 19, 2017 9:02 pm

Do you think i can achieve this PTP link with 5ghz ?

Fri Aug 16, 2019 10:54 am

Hi Everybody
i installed for test purposes and for the first time an LHG 2 XL on the roof of my house
My goal was to test the possibility to do a PTP link of 2.7 Km with partially obstructed line of sigth. The final objectiv is to install optical fiber on the distant place, to get good bandwith in my house (currently at max 5Mb/s using ADSL)

Edit :
I got some answers by myself, and i was using so much more power for transmitting than i though. lot of information below are false, due to "first time" ;)... but the question remain : will 5ghz will help or not ?


i look on 2 tools before installing the antennas:
- http://www.heywhatsthat.com/
- radiomobile

on the first website, here is the line of sight given:
capt1.PNG
On radio mobile here is what i got
capt2.PNG

After installing, here are the information given by both sides: at 20 dbm wich is the legal level for 2.4 ghz in france (17dbm set in tx power)
Edit: wrong, in fact i was transmitting at 17dbm but i forgot to add the 21 dbm of antenna...

Home:
capt3.PNG
Distant site:
capt4.PNG

As you can see, link is established , but with a very very bad CCQ.
i played a little with the antennas:
- swiched to debug country
- forced frequencey to 2372 Mhz 20/40 Ce (if i got it right, it mean that i'll go from 2372 to 2412 Mhz in 40Mhz mode)
- still at 20dbm max (17dbm set in tx power) Edit: wrong, in fact i was transmitting at 17dbm but i forgot to add the 21 dbm of antenna...

Home:
capt5.PNG

Distant site:
capt6.PNG

Hu, hoooo much better!
with same tx power i now get between 40 and 50% of CCQ and 50 to 60 Mb/s instead of 4 Mb/s...


I played a little more, increasing TX power to 20 dbm (so 23 dbm total) which is 200 mW (if i'm not wrong) instead of 100 mW
Edit: wrong, in fact i was transmitting at 20dbm but i forgot to add the 21 dbm of antenna...

and the results are:

Frequency: 2412 (legally ok for frequency, not for power)
(I only show the house side)
capt7.PNG
Frequency : 2372 (not OK for frequency, not OK for power)
(I only show the house side)
capt8.PNG
and, on 2372, with 400mw (26 dbm if i'm not wrong), i get 100 Mb/s.
Edit: wrong again...
(and still 20 on 2412 Mhz)

It seems that the problem is not really the power (23 dbm helped for sure.) but too many people in 2.4 ghz band, right ?
Edit: Wrong, 2 problems: not enough power if i stay at 100mw, i must go to 250 mw minimum to get stable link. and also too much people in the 2.4ghz band perhaps...

so, based on these results, and the fact that in the line of sight there are 1 house + few trees, do you think i can get good results using 5Ghz DFS ?
if i'm not wrong, DFS allow us to use 500 mW , and even 1W if the frequency is not used ?
i would like to try with LHG XL 5 ac (27 dbi)
do you think it's feasible ? or should i abandon this project and keep my poor 5Mbs/ ?

for infromation, i also watched on ubiquiti website (they have a nice tool for ptp estimation)
and here is the line of sight: there is a house + few trees on the line of sight.
capt9.PNG
Thanks a lot for helping !
and sorry for these dummy questions.
i can provide more information if needed.
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Last edited by warenbe on Fri Aug 16, 2019 12:03 pm, edited 2 times in total.
 
warenbe
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Posts: 3
Joined: Fri May 19, 2017 9:02 pm

Re: Do you think i can achieve this PTP link with 5ghz ?

Fri Aug 16, 2019 11:59 am

After searching more information, i understood that 21dbm of gain is added to the tx power

so i fact of using 200mw as i though, i was using more than 5w...

using 250 mw (gain 21dbi + 3tw power manually set) , i'm able to get a link at -81/-84
CCQ is between 7% and 18%
data rate is 7.5Mb

and it's by using 250mw instead of 100mw legally allowed...

the question remain : will 5ghz and DFS might help ?
i don't think.
i'm not even sure it's possible to establish a link more than few hundred meters in france :(

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