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  1. #1

    How strong should a signal be over 3km?

    Model : CPE510

    Hardware Version :

    Firmware Version : 2

    ISP : [/COLOR]

    Hi,

    I've managed to set up a link between two houses around 3km apart. taken a while and alot of head scratching. However i'm not getting a very strong link what is normal or what should i be trying to get? Thanks
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  2. #2
    There are many factors that influence the quality / stability of a wireless link ... starting from the basic alignment, LoS, Fresnel, Electromagnetic noise, distance / power settings, type / length of cable used to power and connect equipment etc. ...

    What I can see in your link,

    1.- for that distance, has low power, only 17 dBm (50mW) is little for what gives the device 27 dBm (500mW) ..., raising the power technically should improve the link, the decent connection values It should improve the Signal Strength from -87 to -65 which is optimal ... the SNR should be up to 35dB minimum ..., the CCQ Transmit should rise to 95% and remain stable without oscillations ..., this alone to get started...

    2.- Regarding Noise Strength, I see that it has a lot of electromagnetic noise, an excellent value is between -103 to -101, good from -100 to -98 and bad from -97 onwards ..., all this just watching the capture From your status tab ...

    Should take into account all the above to improve your link ...

    Regards...
    Victor A. Ramos M.
    va.somar.m@gmail.com
    WhatsApp +51980989627

    ==== if you want to send a personal message, consider my time zone (-5GMT Perú)====
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  3. #3
    Hi victor,Thank you for your very informative reply to my question I appreciate it. With regarding the power output how do I adjust this this to make it more powerful is there a setting somewhere to boost the power? I've got some new masts coming so should be able to have the device higher in a few days time to help as well. Thanks again.

  4. #4
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    Quote Originally Posted by baldog View Post
    With regarding the power output how do I adjust this this to make it more powerful is there a setting somewhere to boost the power?
    Beware that raising power might violate regulatory provisions of the country you are living in. 17 dBm power + 13 dBi antenna gain equals 30 dBm, which is 1 watt. In many countries, this is already the maximum limit allowed. You should at least know this before getting into trouble. In which country you are living?

  5. #5
    Quote Originally Posted by Victor Ramos View Post
    1.- for that distance, has low power, only 17 dBm (50mW) is little for what gives the device 27 dBm (500mW) ..., raising the power technically should improve the link, the decent connection values It should improve the Signal Strength from -87 to -65 which is optimal ... the SNR should be up to 35dB minimum
    Victor I'm under the impression that the values you quote here are unfair to say the least.

    An SNR of -35dB means you're effectively sitting on 100% signal which is considered to be 'optimal' in terms of achieving a 1-to-1 (100%) theoretical Rx/Tx to selected MCS parity. No way is this even an implied prerequisite however to get a good throughput out of a wireless link. I've been getting 3/4 of a theoretical max with 25-28dB SNR in many many cases which I find pretty darn good for links over 3km away with clear LoS and clear freshnel zone.
    Last edited by RTouris; 04-10-2017 at 09:40.

  6. #6
    Thanks for the heads up. I'm in the UK, do you know what the max power output is for here? Do you have any other ideas for increasing the signal or is it just a case of moving the CPE's until i find a good location? Thanks

  7. #7
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    Quote Originally Posted by baldog View Post
    Thanks for the heads up. I'm in the UK, do you know what the max power output is for here? Do you have any other ideas for increasing the signal or is it just a case of moving the CPE's until i find a good location? Thanks
    Maximum allowed EIRP in the UK is 30 dBm (~ 1,000 mW). So, for the CPE510 17 dBm + 13 dBi antenna gain equals 30 dBm, so 17 dBm TX power is already yielding the maximum EIRP and it is 1,000 mW, not 50 mW. You always have to take into account the antenna gain of the device, not only TX power.

    The maximum TX power the CPE510's universal hardware can achieve (in TEST mode) is 23 dBm, not 27 dBm. This yields 23 dBm + 13 dBi = 36 dBm, which is 3.981 Watts or 3,981 mW. But the EU hardware is fixed to 17 dBm, no TEST mode anymore.

    To achieve best results, use 20 MHz channel width, fixed 802.11n mode and correct distance setting (you can leave it at auto setting as long as it shows 3 km distance on the Status page). Make sure that the antennas of both CPEs are carefully aligned to each other.

    To calculate the 1st fresnel zone and the 60% clearance zone, use the Air Link Calculator and set your coordinates on the map correctly: https://airlink.ubnt.com/#/

    For a setting comparable to TP-Link's CPE 510, select 5 GHz, Airmax, 13 dBi antenna gain, maximum EIRP of 30 dBm and mounting height in the Calculator. This will show you the fresnel zone.
    Last edited by R1D2; 04-10-2017 at 21:19.

  8. #8
    I believe you are already at max. setting as 17dB is indeed the max for Europe.

    Since you're not getting a region setting drop-down selection menu this means you're running latest generation gear that have the restrictions hardcoded into the device, hence you don't get the chance to alter it.

    Clear Line Of Sight as well as a clear freshnel zone must be considered a given in long distance links to establish a good throughput, so I'd begin with these two first before optimizing the link further which in summary involves selecting 20Mhz-only or even 10Mhz-only channel widths and reducing (in general) the MCS setting so that you can inversely increase the SNR out of your link and get a steadier throughput.

  9. #9
    Ok i'll try going down to 20 Mhz. All i'm trying to do is get the net from another house that has fibre as the one im using now gets 0.5mbs so even if the link only gets around 20 mbs id be happy!

  10. #10
    Hi, I've managed to get a pole that's 10 meters high and along with your setting recommendations i have a link!! rx rate seems to drop from 43 mbs to 6 and then back again but it works

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  11. #11
    Try reducing your MCS rate from 15 to 12 you'll probably manage 1-2dB more

  12. #12
    Sorry what does mcs stand for/how do i alter it?

    Now I've managed a link between the two sites how do i go about plugging this into my lan? I've got an asus router with wan in however when i plugged it in there the two routers on died due to ip conflicts. I'd like to keep things separate so there would be one lan at one side and another at this side?

    Thanks for all the help everyone has provided

  13. #13
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    Quote Originally Posted by baldog View Post
    Sorry what does mcs stand for/how do i alter it?
    MCS = Modulation and coding index. Boring tech stuff, what's important to the average user is the resulting wireless speed, which depends on channel width and mode. See http://mcsindex.com/ if you are interested in the nitty-gritty details.

    Now I've managed a link between the two sites how do i go about plugging this into my lan? I've got an asus router with wan in however when i plugged it in there the two routers on died due to ip conflicts. I'd like to keep things separate so there would be one lan at one side and another at this side?
    If you use client mode to connect to the AP, you will get one big local area network. Make sure the IPs of all devices in the LAN are unique.

    If you rather use AP client router mode to connect to the AP, this will result in two LANs: one the AP and the wireless part of the client are members of and one the wired devices are member of. Make sure to read the documentation carefully, it's somewhat challenging to configure this mode.

  14. #14
    Ah ok thanks. So i'm presuming you mean knock the channel width down to 10MHz?

    Is there a 'how to' i'm able to follow anywhere to set the two sites up as separate lans or would you be able to give me a rough idea?

    Thanks

  15. #15
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    Quote Originally Posted by baldog View Post
    Ah ok thanks. So i'm presuming you mean knock the channel width down to 10MHz?
    Makes no sense IMHO. In the 5 Ghz band, WiFi channels don't overlap, so you can use the full channel width of 20 MHz if there is at least one free channel.
    The transmission power will not change by reducing speed, only the modulation codecs, which could improve signal-to-noise ratio (SNR). But you have to try at the installation site to find out. Much more important is correct antenna alignment to improve signal strength/SNR.

    Is there a 'how to' i'm able to follow anywhere to set the two sites up as separate lans or would you be able to give me a rough idea?
    Setup is straightforward. In AP client router mode, the WiFi radio link operates as a client connecting to the remote AP. Additionally, routing functions are available for wired devices and wireless devices if you also use the local AP. See the docs, in section Operation Modes (page 9) to get a more clearer picture of what this mode does despite regular client mode:

    http://static.tp-link.com/PharOS(UN)...881566519n.pdf
    Last edited by R1D2; 04-15-2017 at 19:58.


 

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