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3km wifi linktest from a Mikrotik Omnitik to a SXT G-5HPnD-HG r2 with obstacle

Device site A

OmniTIKU-5HnD

Device site B

SXTG-5HPnD-HGr2

  • The linktest was executed taking into account the legal limitation of 1 Watt ERP (effective radiated power).
  • Speed is being measured with the bandwidth tool of the Mikrotik SXT.
  • This 3 km 5 GHz wifi linktest was executed on a bridge.
  • The Omnitik in 30 meters high, the SXT 8 meters of the ground, on a bridge.

Linkplan

Total distance: 3 km.

This is the bridge

Situation

There is a construction crane in between the line of sight and some concrete silo's are in the "fresnel zone". This is asking for trouble, most certainly not a stable wifi link.

The red marking indicated the fresnell zone, being blocked by the concrete structures.

Way of working

In order to measure the speed between both antennas, we connect the SXT directly to the laptop. The measuring is being executed by the bandwidth tool of the SXT itself, since we will not generate excessive speeds. The SXT was configured as client-bridge and connects to the Omnitik. The Omnitik was configured as accesspoint and DHCP-server. The SXT is powered by a 24V-battery.

Measuring.

Results
Bandwith20 Mhz protocol 802.11 n
Frequentie Power Bandbreedte Ack-timing Signaal Speed RX/TX Transmit ccq
5200 Mhz 1 watt erp 20 Mhz 4 km -66/-70 dBm 13,9/22,5 Mbit rx/tx 82/58 rx/tx

Pingtest

The pingtest overall shows an unstable data transfer. In a short timeframe, you see some "peaks" of 7 and 8 msec.

The link is not stable to realize a good performance. Reason for this: the construction crane and the concrete silo’s. This is an example to show that a link must meet certain specific criteria in order to function well. There’s no other way.

  • There needs to be clear line of sight, no obstacles in the way.
  • The fresnel zone must also be clear of obstacles.
  • Put the access point and the client high enough to get a free fresnel zone.

Know more about the prerequisites? Read it here.