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ema81
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Joined: Sat Oct 12, 2019 7:59 pm

LHG52AC with superchannel: PA risks?

Wed Jul 01, 2020 9:15 pm

Hi, I'm using two LHG 52 AC (RBLHGG-5HPacD2HPnD), ROS 6.44.5, for a link of about 4km, no obstacles. I managed to get a throughput of about 350-380Mbps on the 5ghz band, and about 80 Mbps on the 2.4ghz band. Since the goal was to share an asymmetric internet connection, I decided to split the download and upload traffic via OSPF and MPLS to maximize the throughput (no continued tx/rx switch on both LHGs)

In the last 3 weeks, however, the capacity on the 2.4ghz section has drastically decreased (about 40mbps) probably due to some noise: now I'm using 2407 mhz as frequency (20/40Mhz Ce, N) and I would like to go to a lower frequency, since I am licensed.

Originally, freq was 2387 mhz, then I moved because I started experiencing "strange" problems: in practice, the signal received by only one of the antennas fluctuated continuously, without variations in the noise floor, 10dB lower, and then stabilized on a very low value (12-13 dB lower).
Changing the frequency, the situation has not improved immediately, but about ten days later, first with a fluctuation (opposite than before) and, in the end, with original dB values.

In short, I am afraid that setting my LHGs at a lower frequency than the standard ones could make a damage at them, so now them are set at higher and standard freq.

It is possible that bringing those devices to those frequencies ( <2400mhz ) can damage PA or the receiver, or the problem has to be found in interference or other? (although the scan or frequency usage functions do not indicate anything relevant and the NF is always very negative)

Thank you
 
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ryny24
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Re: LHG52AC with superchannel: PA risks?

Mon Jul 12, 2021 11:24 pm

Hi, I'm using two LHG 52 AC (RBLHGG-5HPacD2HPnD)
Would you mind sharing your config? I have tried several times to get a link with these, but my signal level is always horrible. -70 to -80. I think I have a setting wrong, and it's not transmit power. I switch to an AF5X and I'm working great!

Thank you.
 
r00t
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Re: LHG52AC with superchannel: PA risks?

Tue Jul 13, 2021 3:43 am

Your problem is likely caused by interference. The WIFI PAs are made so they can tolerate high SWR antennas and usually have internal protection in case antenna is completely disconnected so they can't be easily damaged. As for superchannel, there is really no difference for PA if it's few MHz out of band. Only possibility I can think of is SAW filter that may become damaged if it's too narrow and you pump full power to it, but usually these are before PA on TX side (to clean any TX out of band interference).
Too bad it's AC unit and there is no spectral scan supported (really.., wtf mikrotik...), as that's the only way to monitor and detect non-WIFI interference.
 
ema81
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Re: LHG52AC with superchannel: PA risks?

Wed Jul 14, 2021 3:36 pm

Hi, I'm using two LHG 52 AC (RBLHGG-5HPacD2HPnD)
Would you mind sharing your config? I have tried several times to get a link with these, but my signal level is always horrible. -70 to -80. I think I have a setting wrong, and it's not transmit power. I switch to an AF5X and I'm working great!

Thank you.
Here is my config (only for one side: other is mirrored)
/interface bridge
add admin-mac=00:00:5E:80:FA:10 auto-mac=no mtu=1500 name=Bridge-LO
add admin-mac=00:00:5E:80:FA:11 auto-mac=no mtu=1500 name=bridge1 \
    protocol-mode=none
/interface vpls
add disabled=no l2mtu=1500 mac-address=02:D6:B3:D9:9D:DC name=vpls1 \
    remote-peer=192.168.88.125 vpls-id=1:1
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
add authentication-types=wpa2-psk eap-methods="" management-protection=\
    allowed mode=dynamic-keys name=Fiber supplicant-identity=""
/interface wireless
set [ find default-name=wlan1 ] band=2ghz-b/g/n channel-width=20/40mhz-Ce \
    country=no_country_set disabled=no frequency=2402 frequency-mode=\
    superchannel mode=station-bridge name="Fiber - 2G" \
    nv2-security=enabled radio-name=hidden2G scan-list=2402 security-profile=\
    Fiber ssid=FB2 wireless-protocol=802.11 wps-mode=disabled
set [ find default-name=wlan2 ] band=5ghz-onlyac channel-width=\
    20/40/80mhz-eCee country=no_country_set disabled=no frequency=5905 \
    frequency-mode=superchannel hw-retries=15 installation=indoor mode=\
    station-bridge name="Fiber - 5G" nv2-security=enabled \
    radio-name=hidden5G scan-list=5905 security-profile=Fiber ssid=FB \
    station-roaming=disabled wireless-protocol=802.11
/interface wireless nstreme
set "Fiber - 2G" enable-nstreme=yes
/routing ospf area
set [ find default=yes ] disabled=yes
add area-id=0.0.0.1 name=fiber-backhaul
/routing ospf instance
set [ find default=yes ] router-id=192.168.88.121
/interface bridge port
add bridge=bridge1 interface=ether1
add bridge=bridge1 interface=vpls1
/ip address
add address=192.168.88.129/30 interface="Fiber - 5G" network=\
    192.168.88.128
add address=192.168.88.134/30 interface="Fiber - 2G" network=\
    192.168.88.132
add address=192.168.88.121/30 interface=Bridge-LO network=192.168.88.120
add address=10.222.0.3/29 interface=bridge1 network=10.222.0.0
/ip dns
set servers=8.8.8.8,8.8.4.4
/ip route
add distance=1 gateway=10.222.0.1
add distance=1 dst-address=192.168.1.0/24 gateway=10.222.0.4
/ip upnp
set show-dummy-rule=no
/mpls ldp
set enabled=yes lsr-id=192.168.88.121 transport-address=192.168.88.121
/mpls ldp interface
add interface=Bridge-LO
/routing ospf interface
add cost=20 interface="Fiber - 2G" network-type=broadcast
/routing ospf network
add area=fiber-backhaul network=192.168.88.128/30
add area=fiber-backhaul network=192.168.88.132/30
add area=fiber-backhaul network=192.168.88.120/30
/snmp
set enabled=yes
/system clock
set time-zone-name=Europe/Rome
/system identity
set name=Backhaul-F
/system ntp client
set enabled=yes primary-ntp=193.204.114.105 secondary-ntp=51.145.123.29
 
ema81
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Topic Author
Posts: 6
Joined: Sat Oct 12, 2019 7:59 pm

Re: LHG52AC with superchannel: PA risks?

Wed Jul 14, 2021 3:41 pm

Your problem is likely caused by interference. The WIFI PAs are made so they can tolerate high SWR antennas and usually have internal protection in case antenna is completely disconnected so they can't be easily damaged. As for superchannel, there is really no difference for PA if it's few MHz out of band. Only possibility I can think of is SAW filter that may become damaged if it's too narrow and you pump full power to it, but usually these are before PA on TX side (to clean any TX out of band interference).
Too bad it's AC unit and there is no spectral scan supported (really.., wtf mikrotik...), as that's the only way to monitor and detect non-WIFI interference.
Thanks for the reply and for the clear explanations. After the much desired vacation, I will try again to set a lower frequency. And just in case to do a spectrum scan, if I will find an analyzer.

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