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Thread: Erratic Signal Strength

  1. #1

    Default Erratic Signal Strength

    Hello,

    I have a building with two access points, same SSID, operating on the same channel. Users can roam from one AP to the other. The signal on one of them looks erratic. I wonder if being on the same channel is causing this.
    Please see attached Inssider screenshots.

    Thanks.

    Click image for larger version. 

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  2. #2

    Default

    Hello,

    Tough to say for sure. If you move closer to the other AP, does it have the same Erratic Signal? Couple things you may want try if possible would be to turn off the other AP and see if the RSSI stabilizes. If it does then you can be pretty sure that there is inference between the two. You might try if possible, would be to swap the AP's and see if the problem stays with the AP or stays with the location. If it follows the AP the issue may be with the AP, and if there is an firmware upgrade you might try it. However if you are not having connection issues on this AP and it is working fine you may not want to do that. I am a proponent of if it is not broke don't fix it. If the problem stays in the location then it probably is something in that area that is causing it.

    Rich

    Rich

  3. #3

    Default

    Dunno if what I am experiencing is similar. I have a Linksys wrt160n V2 running stock Linksys firmware that has a very stable db reading (red line in attached image) and another Linksys E2000 with external antennas that I added running DD-WRT which is fluctuating in db strength (green line in attached image). Both routers work fine but I wonder why the E2000 does not have the stable db strength. I also would have thought the db strength of the E2000 would be higher because of its external antennas.



    Note: I was connected to the wrt160n (and of course running inSSIDer) when this image was taken.
    Last edited by careh; 04-29-2011 at 05:16 PM.

  4. #4

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    nstrahm,

    I see you are running a linksys. What model is yours and is it running DD-WRT? careh is seeing similar results with his linksys. wondering if it may be a AP issue.

    Rich

  5. #5

    Default

    A user at DD-WRT forums reported the same problem when he attached the external 7dbi antennas to his E2000. Now to figure out if it is DD-WRT or the antennas.

  6. #6

    Default

    Make sure that you Disconnect your wireless laptop card from the AP when you are taking those measurements. I have found that sometimes when you are connected to an AP, the AP you are connected to looks more level (in a graph) & will go up and down. However, then the others are not really changing in signal strength, hence it is not looking at them anymore. You basically want your computer to continue to search for AP's around, but sometimes when you are already connected it doesn't do that as much or at all (in some cases).

    Many times AP's send out their "SSID" (name) at full power - spike and drop down after that. Sometimes that will account for variations in large highs-and-lows, however the person above was in the 20-30 dBm range. That could also just be a way to strong of signal - no one likes it when you turn your stereo up to 9/10 and cannot understand anything because of all the distortion...Radio's are the same way.

    Best option disconnect from AP and run test.

    Oxygen
    Last edited by oxygen69; 04-29-2011 at 02:10 PM.

  7. #7

    Default

    After disconnecting the external antennas - for about the first minute the fluctuations were still there - then they went away.






    I tried running isSSIDer while not connected to either AP but got no signal levels showing at all. Even when I re-connected to one of the AP's I had to close and re-start inSSIDer to see any readings.
    Last edited by careh; 04-29-2011 at 02:21 PM.

  8. #8

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    Reboot everything, AP computer ect.. and try again..

  9. #9

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    After a reboot I still did not have much luck in running inSSIDer without being attached to an access point - but I did notice that if I switched between the 2 AP's then the AP without my laptop attached to it displayed that fluctuating behavior so I am now wondering if that fluctuating is related to an AP not connected to a PC running inSSIDer - and once it has connected to my computer it stops fluctuating. In this image the first half is when I was connected to the E2000 - and its db line is level while the wrt160N is fluctuating - 1/2 way through I switched to connect to the wrt160N - and at that point the E2000 line starts to fluctuate while the wrt160N line goes flat.



    Since this post a second laptop was turned on and attached to the wrt160N. I then attached my laptop to the E2000 and thought I would see two 'flat lines' as each router had a computer talking to it. Not so - the router that I was attached to would have the flat line and the other router would fluctuate. I wish i could run my inSSIDer without being attached to an AP but no luck doing that so far.
    Last edited by careh; 04-29-2011 at 03:51 PM.

  10. #10

    Default

    That would make me think it is the PC's Wireless Network card. I took a look and E2000 and the WRT160N to see if they used the same chipset. The E2000 uses a Broadcom BCM4717 and depending on HW version of the WRT160N; 1.0 = Broadcom 470; 1.1 = Broadcom 470 Rev. 9; 2.0 = Ralink RT2880F; 3.0 = Broadcom 471. Probably does not tell us much, but though it worth noting. I really find it interesting how the fluctuation is repeated exactly the same over time. You can literally take a small section of this heartbeat, for better lack of a word, and it would overlay almost on top of the same line a little further along. When I run inSSIDer here in the office I don't see the same behavior.

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