WiFi Interference

Forum to discuss the Rikomagic MK802 Mini PC

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WiFi Interference

Postby twinspark » Thu Jun 28, 2012 10:34 am

Hi All,

I've had my mk802 just over a week. For the first few days everything was great, but it seems to have developed an issue where it's killing my WiFi signal!

To cut a long story short, and by process of elimination, I've definitely sourced the problem to the mk802. The following is reproducible each time I test: -

    1. With mk802 unplugged, test my WiFi. (For fairness, I'm ensuring only one device is using WiFi. I've also ensured, using the inSSIDer application, that my router is using a channel unused by other nearby routers)

    2. Using speedtest.net and broadbandspeedchecker.co.uk, I get a very consistent, steady 4mbps download.

    3. At this point I power on the mk802 and instantly my WiFi is utterly crippled. For example, both speedtest sites show 0.01mbps at best; most of the time they can't connect to perform the test. The interesting thing is this happens before Android has had chance to boot - it's from the moment the mk802 has power.

    4. The second I unplug the mk802, my WiFi returns to normal: The second I plug it back in - my WiFi becomes unusable again. I've performed this test many times now and it's 100% reproducible - so I'm confident I've narrowed it down to this.

I've tried changing the channel of my router, but the mk802 seems to be 'jamming' all of them (1-11). Without an RF analyser it's difficult to say with certainty, but it does seem that it's randomly spewing 2.4Ghz

I was just wondering (hoping) somebody else had experienced this and possibly had a solution!
I'm unclear whether this would be a firmware or hardware fault, although I'm guessing the latter?

Many Thanks!
twinspark
 
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Re: WiFi Interference

Postby twinspark » Thu Jun 28, 2012 10:29 pm

Hi All,

I have a little more information on this... I hope it means something to somebody!

I believe I've traced the issue a little further - specifically to the HDMI cable!

As per my previous post I repeatedly conducted the same test - this time without the mk802 connected to either my TV or Soundbar.

The previous issue was not reproducible!

However, as soon as I connected the mk802 to the TV or Soundbar the WiFi signal in my house is severely affected.

I also noted: -

    1. If the HDMI cable is attached to the mk802, but the other end is not connected to anything - the issue does not occur
    2. As soon as the other end of the HDMI cable is connected to either the TV or Soundbar it has an immediate, and severe effect on my WiFi

I think this lets me rule out a firmware problem at least!

Can anybody make sense of this!? Is my mk802 turning whatever it's connected to into a giant 2.4Ghz transmitter jamming all WiFi within a quarter mile radius - like some accidental Tesla coil! :D ?

Thanks.
twinspark
 
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Re: WiFi Interference

Postby twinspark » Fri Jun 29, 2012 9:44 pm

I found this article http://www.avforums.com/forums/hdmi-cables-switches/269332-hdmi-causes-rf-interference.html which got me thinking the supplied mini HDMI > HDMI cable was potentially to blame.

I purchased another cable, hoping a higher quality one would have better shielding and therefore be less susceptible to causing interference. Unfortunately the problem persists so I'm running out of ideas now :cry:
twinspark
 
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Re: WiFi Interference

Postby EnvyThisStuff » Sat Jun 30, 2012 4:27 pm

Unfortunately it sounds like up to three things need to be replaced at this point: the MK802, the cable, the monitor. You say the cable did not help. If I'm understanding you, the wifi gets messed up whether connected to a TV or to a monitor. That effectively rules out the monitor since it's unlikely you have two broken output devices (unless you "zapped" them both under some other previous setup?). That leaves changing the MK802 :( Might be other choices still, but not sure what they'd be.
Run into a problem? Need ***Mini PC/MK802 services***?
(installing firmware, installing LINUX, getting/setting up SD cards, etc)
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Re: WiFi Interference

Postby sciurus » Tue Sep 11, 2012 6:54 pm

I also have this problem. When I try to connect from my MK802 II to one of my wireless routers, it kills all my other devices connections and fails to connect itself. I set up a different wireless router and am able to connect to it okay.

Because of the way my TV is designed I cant plug in to the hdmi port without using the supplied cable, and my monitors do not have hdmi ports. I've ordered another hdmi cable to try with the TV, as well as an adapter that will let me hook my MK802 II up to a monitor via a DVI cable, to test if the supplied cable is a part of the problem.
sciurus
 
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Re: WiFi Interference

Postby Tophe » Wed Sep 12, 2012 7:32 am

Hi,

I just receive my MK802 II.

I manage to etablish link with my wifi access point easily. But transfert rate is very poor (about 100Ko/s for a b/g wifi type). And of course, i'm only few meters for antenna, and other devices (Iconia A500, Archos 43It) work correctly.

Later, my wife ask me if wifi access is working, because she faces slowdown with her Nexus S. I stops MK802 II, and everything return to normal for her.

I try a second access point on my routeur (no protection, for testing), and same issue.
I'm missing the small cable for HDMI. I will try without it tonight.

I also update it with lastest firmware (far better than original one). It's a smart device, despite wifi slow down :( It's so slow, I'm unable to read video from NAS.

Still investigating.

Tophe
Tophe
 
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Re: WiFi Interference

Postby stevhorn » Wed Sep 12, 2012 9:55 am

Interestingly, I have this exact same problem with my Raspberry Pi. I do not have this problem with my MK802 II. This leads me to believe that my Raspberry Pi is faulty, and probably so is your MK802 II. I suggest RMAing your MK802 II.
stevhorn
 
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Re: WiFi Interference

Postby Tophe » Wed Sep 12, 2012 2:05 pm

Hi,

I receive my mk802 II last night. And I face the same issue.
When plug with HDMI short cable, my wifi is jamming, mk802 II has very slow transfert rate, and other wifi device face the same issue.

Still looking for a solution.

Tophe
Tophe
 
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Re: WiFi Interference

Postby 80sman » Thu Sep 13, 2012 6:20 am

I have this problem with my mk802 original version.

When it is connected I have carried out speed tests and the upload speed is about 3 times faster than the download.

I've mounted heat sinks on the chips in case it's a heat issue, to no effect.

I've also read of other android devices with similar problems running ics.

Still not sure if it's a hardware issue or software. I was thinking of replacing the antenna next.
80sman
 
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Re: WiFi Interference

Postby luke123 » Thu Sep 13, 2012 11:46 pm

Is it possible to disable the MK802 II's antenna under ICS, and use an external WiFi client (connected via a powered USB hub)?

Thanks.
luke123
 
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