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5 GHz Wifi

Posted: Wed Sep 11, 2019 3:15 pm
by sergiop
Is it critical to use with Mikrotik RB912UAG-5HPnD-OUT and other model Wifi Antena 5 GHz when use in in 5 GHz mode?
In case I have 2.4 GHz antena and use it in 5 GHz, what problems it may provide?
Thanks

Re: 5 GHz Wifi

Posted: Wed Sep 11, 2019 8:58 pm
by mkx
It is quite vital to use antenna for correct requency band. If you use wrong antenna, in best case the signal will suck as the antenna gain will be low (could be something like -10 dBi or even lower instead of +3 dBi or +6 dBi). In worst case the PAs might get destroyed due to high VSWR.

Re: 5 GHz Wifi

Posted: Fri Sep 13, 2019 11:48 am
by sergiop
Thanks for info. In my case is it possible reason the board goes to reboot after some wifi device connected to it...

Re: 5 GHz Wifi

Posted: Fri Sep 13, 2019 12:28 pm
by mkx
AP probably shouldn't reboot when some client connects to it. It is possible though and I can think of a few reasons for it.

One is weak power supply adapter. When client connects, AP will start to transmit at higher (full) power because of improper antenna (with too low gain). Thus it's causing higher power draw from the power adapter. If that one can not supply demanded current, voltage will drop causing AP to restart.
But this might happen even if you use proper antenna ... under full wireless utilization.

Another reason might be some peculiarity of WiFi subsystem - when improper antenna is connected (too high VSWR), WiFi power amplifier might enter into some trouble triggering SoC to bail out.