Community discussions

 
warenbe
just joined
Topic Author
Posts: 13
Joined: Fri May 19, 2017 9:02 pm

Help me increase quality of this 3km link

Wed Sep 11, 2019 2:17 pm

Hi
i established a 3 km link with LHG XL 5 AC

i have some question relative to quality of signal i can't find answers. Can you help me ?

Question 1:

using
  • France regulatory domain
  • 20/40/80 Mhz XXXX selected
  • frequency 5240/20-eeeC/ac/P(-4dBm)
  • Antenna gain 27 db
  • NV2
  • Freq usage show 1.5 % of usage
  • SNR is 37 db
i get -71 dbm signal, 70 Mb/s down TCP in NV2

using
  • France regulatory domain
  • 20/40/80 Mhz XXXX selected
  • frequency 5620/20-eeCe/ac/DP(0dBm)
  • Antenna gain 27 db
  • NV2
  • Freq usage show 0 % of usage
  • SNR is 30 db
i get -77 dbm signal, 40 Mb/s down TCP

why so much difference ?
it should be better with the second solution as there is nobody using this frequency, no ?
increasing TX power to 1w (+3db) does not change anything at all :(

Question 2:

on the 5240 Mhz settings, when i use NV2 i get quite stable 70 or 80 Mb/s (depending on the time of the day.)
with 802.11 i get a faster conneciton, but very unstable, with constant drops...
nv2.PNG
802.11.png

why do i get these drops using 802.1 ?
Why is CCQ so low ??
please note that 100mw, 200mw or 500 mw of power get exactly the same signal quality or CCQ quality using the same frequency.

How i can increase the quality of the link ?
You do not have the required permissions to view the files attached to this post.
 
mistry7
Forum Guru
Forum Guru
Posts: 1314
Joined: Tue Oct 13, 2009 11:57 am
Location: Germany

Re: Help me increase quality of this 3km link

Wed Sep 11, 2019 11:50 pm

Clear Los?
I think your allignment is Bad
 
warenbe
just joined
Topic Author
Posts: 13
Joined: Fri May 19, 2017 9:02 pm

Re: Help me increase quality of this 3km link

Thu Sep 12, 2019 1:43 am

Hi
Thanks for the answer
if by LOS you mean "can you see the other antenna" : yes (even if i need magnifier)
if you mean "does the fresnel is completely clear": i'm really not an expert, i don't know the "size" of the fresnel area, i think no.
(see edit on the bottom for pictures)


i installed both antennas on 4m high pole, it's the max i can do

Can you answer these questions for my curiosity :

why do i get the drop in 802.1 ? as far as i understand it, speed should go down but not drop to 0 like this, while HW Frames are few hundreds highers than frames.
sometime it can run like a charm for 5 minutes, and suddenly i get lot of drops.

why does NV2 not impacted like 802.1 ?
i also tried to go to 5640 Mhz: this frequency (and the one around) is clear from any signal: but i get worse bandwith: 40Mbs/ (tcp) , and the drop still appears
so, it means that it's not interferences problem right ?

Increasing the TX power from -7db to 3db or even 9db does not increase CCQ and Tx/Rw db a lot (69 db instead of 71)
Increasing the TX power to 23db give -59 db, but CCQ is still at 30 or 50% max. Why don't CCQ increase ?

also, for aligment, i suppose both chain should have exactly the same Tx/Rx level ?
because if i'm running at -7db, both chain has same level (1 or 2 db diff), but as soon as i increase power, the difference start to appear...
chains.PNG
in the same chain, i also have different value for tx/rx : why ? seems illogic for me : if i can speak to someone, he also can speak to me with same level no ?

Edit

here is 2 pictures of one side :
This picture was taken just under the antenna (the Mikrotik antenna is 1.5m upper)
pic2.PNG
as you can see, there are TV antennas near. can these antenna (the one on the left is 1m under the AP and 5m away, the others are ~50cm under and 15m away approx.) be a problem ?

this second picture is a zoom: the other point is where the arrow is.
pic.PNG
so, clearly, if i can see the other side, the fresnel zone is not good i think. right ?
You do not have the required permissions to view the files attached to this post.
 
quackyo
Member Candidate
Member Candidate
Posts: 111
Joined: Mon Nov 16, 2015 10:14 am

Re: Help me increase quality of this 3km link

Thu Sep 12, 2019 9:49 am

Try 40MHz (or 20Mhz) channels.
A stable 40Mhz or 20Mhz link is better than a flaky 80MHz.
 
mistry7
Forum Guru
Forum Guru
Posts: 1314
Joined: Tue Oct 13, 2009 11:57 am
Location: Germany

Re: Help me increase quality of this 3km link

Thu Sep 12, 2019 9:57 am

Here the Calculations:

5600 Mhz, 3km, 27dbI, 30dBm allowed


Signal: -59.96db
FSPL (free space path loss): 116.96db
Fresnel-Zone ideal (80%): 7.16m
Fresnel-Zone OK (60%): 5.37m



So your Signal should be something like -60db, yours is 10dB off,
and this is the reason why this link don't work as expected.

-check alignment
-mount Antennas higher


ncreasing the TX power from -7db to 3db or even 9db does not increase CCQ and Tx/Rw db a lot (69 db instead of 71)
Increasing the TX power to 23db give -59 db, but CCQ is still at 30 or 50% max. Why don't CCQ increase ?
Power never brings the same benefit as prober Antenna alignment and Clear LOS!
The next thing is, how polluted is the band at this envoirement?

mistry7
 
warenbe
just joined
Topic Author
Posts: 13
Joined: Fri May 19, 2017 9:02 pm

Re: Help me increase quality of this 3km link

Thu Sep 12, 2019 10:38 am

Hi
Try 40MHz (or 20Mhz) channels.
A stable 40Mhz or 20Mhz link is better than a flaky 80MHz.
using 802.1
20/40/80 Mhz : 106 Mbps with lot of drops
20/40 Mhz: 85 Mpbs with lot of drops too.
20 Mhz: 55 Mbps with lot of drops

so changing it does not remove drops.
also, i would expect to get 100 Mbps with 40 mhz (double frequency = double speed, right ?)

So your Signal should be something like -60db, yours is 10dB off,
do you have a website or anything calculating this ? i would like to calculate it with all frequencies i try

ok so it's perhaps mix problem:
- for sure fresnel is not at 100 or 80%. i'll check how to calculate it
- wrong alignment


i tried to align as best as i can. as soon as i move even very slighlty horizontaly or verticaly, i loos db. so i though it was ok... but i did not checked the vertical alignment of the other antenna yet.
I'm not sure i can mount antenna higher...

in your calculation you said :
5600 Mhz, 3km, 27dbI, 30dBm allowed

you agree with me (yep, stupid question i think) that the max tx power of the card can be 3 db ? i mean : the eirp is 27 db of gain + 3 db tx power ?


about pollution, i checked with snooper and freq usage

Point A (the one with pictures above)
freq_usage_pointA.PNG
snooper_pointA.PNG
Point B
freq_usage_pointB.PNG
snooper_pointB.PNG
5240 or 5260 work better than 5600 wich is less poluted :o
that why i find it strange
but perhaps, 5200->5600 change a lot in the capacity and acceptance of bad alignment ...


in any case, thanks for helping me ;)
You do not have the required permissions to view the files attached to this post.

Who is online

Users browsing this forum: No registered users and 23 guests