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Old 01-15-2016, 08:44 PM   #1
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Default Scanning for WiFi interference

I have noticed that the baby monitor my parents gave us is affecting our home WiFi network. It was most apparent when I had the monitor sitting next to my laptop and found that my normal 18 Mbps was down to 5 or 6 Mbps. As soon as I moved the monitor away, my speed jumped back up to 12-13. When I turned the monitor off completely, it jumped back up to 18-19 Mbps.

A little research showed that the majority of baby monitors are running on the 2.4 Ghz spectrum. What I'd like to do is scan to see where the interference is worst so that I can adjust my router's wireless channel accordingly. However, every program and app that I can find only scans for other WiFi networks, not for non-WiFi interference.

Does anyone know of any programs or apps that do this? I'm not going to buy a $3000 Cisco RF spectrum analyzer just to solve this.
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Old 01-15-2016, 08:54 PM   #2
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You could buy a Tektronix* RF spectrum analyzer instead. RSA306 USB Spectrum Analyzer | Tektronix


On topic: My router has a feature that scans channels for interference. But its also running aftermarket firmware.



*disclaimer, I work for Tek, buy our stuff
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Old 01-15-2016, 08:57 PM   #3
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Not buying $3000

Aidan links $3500 one.

Guess he didn't say he won't pay more

What I'd do is get some packet monitoring going and change channels, try and find the least noisy channel that way.
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Old 01-15-2016, 09:07 PM   #4
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If you want to know which channels are most heavily used by other wifi devices, there are smartphone apps to do that. Note that there are really only 3 non-overlapping channels for 802.11g -- 1, 6, and 11. The intermediate ones all overlap those three.

If you want to look for non-802.11 sources of interference like that baby monitor (or, worst of all, a microwave oven) then you need a device like the one Aidan linked. This is the realm of specialized test equipment, and it tends to be fairly expensive.

--Ian
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Old 01-15-2016, 09:24 PM   #5
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Or, as Aidenj said, log into your router and explore the more advanced options. My last router, which was made by Ξ i♣ea♫1g░P0ṅ (sorry, line noise) and running stock firmware, had this exact feature, where it acted as a primative spectrum analyzer and showed you the detected power on every channel.
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Old 01-15-2016, 09:34 PM   #6
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Router is an Asus RT-N66U on stock Asus/Merlin firmware. There is an "auto" setting for channels but I don't think it shows you any details. Last I looked, leaving it on auto meant it was on channel 6 most of the time.

Is what I'm describing technically possible? It would seem like wifi devices would at least be able to detect RF signals within the wifi spectrums, but maybe not, if the radios are hard coded to only read wifi signals.

[edit: I guess that's exactly what you were saying, codrus.]
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Old 01-15-2016, 09:56 PM   #7
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You could also change the frequency the router operates on and see if it makes a difference, but that depends on the entire network & if all of your devices still connect.

I've used 'WiFi Analyzer' on iphone & android before. Works pretty well. If you walk around your home in a 4 corner point you could possibly interpret where outside signals are coming from if interference is also affecting by watching signals get stronger/weaker.

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Old 01-15-2016, 10:04 PM   #8
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Okay, making a little progress here. I found a thread from someone with the same baby monitor.

Quote:
I found on the Summer Infant website that their video monitors automatically use these three frequencies:

Channel A: 2.410 GHz
Channel B: 2.441 GHz
Channel C: 2.468 GHz
That's not good. That means channel A is just a bit below wifi 1, and channel B is just below channel 7. Channel C is above channel 11 but still within range.

I'm not sure if the post quoted means that the baby monitor is made with one of those three frequencies hard-coded, or if each monitor it can switch between the three. If I had to guess, I'd say they are probably hard-coded to just one of those frequencies.

Since it looks like the router has been on Channel 6, I guess I'll test Channels 1 and 11 and compare. Interference from other WiFi networks is basically nil so that doesn't matter.
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Old 01-15-2016, 10:44 PM   #9
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Looks like Channel 11 is the winner for now. I'll leave it set like that for now and see if there's any noticeable improvement.
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Old 01-15-2016, 10:55 PM   #10
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Put the monitor between you and the router to test.
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Old 01-16-2016, 02:45 PM   #11
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Buy a different baby monitor?
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Old 01-16-2016, 05:52 PM   #12
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Ditch the damn monitor. If the baby really needs attention, you will hear it cry.

Children do not need to be electronically monitored every minute.
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Old 01-16-2016, 09:43 PM   #13
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Quote:
Originally Posted by rleete View Post
Ditch the damn monitor. If the baby really needs attention, you will hear it cry.

Children do not need to be electronically monitored every minute.
I have a coworker whose sub-1-month-old daughter spontaneously stopped breathing and turned blue. Fortunately they caught it, called 911, and she's fine (now 3 and a bit), but SIDS is real.

It's unclear if an audio-only baby monitor would help in that sort of case, but "you will hear it cry" is not always true.

--Ian
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Old 01-17-2016, 11:27 PM   #14
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lulz at negs for wanting to keep an eye on my 8 month old.
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Old 01-18-2016, 01:58 AM   #15
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But seriously, surely not every baby monitor broadcasts over the exact spectrum of standard wifi. Just find one that doesn't.
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Old 01-18-2016, 02:25 AM   #16
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There aren't a whole lot of open frequency's with bandwidth capable of streaming video. I bet it's harder than you think to find that.
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Old 01-18-2016, 03:52 AM   #17
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Quote:
Originally Posted by Savington View Post
But seriously, surely not every baby monitor broadcasts over the exact spectrum of standard wifi. Just find one that doesn't.
Actually, they pretty much do. If you want to just buy a cheap radio and use it, you need to be operating in the unlicensed band, and there isn't a lot of it available. FCC part 15 regulations provide the spectrum from 2.40GHz to 2.4835GHz for unlicensed use. 802.11 channel 1 is centered at 2.412Ghz, and channel 11 is at 2.462Ghz, which is essentially the whole thing.

There is also a 5GHz unlicensed band (used for 802.11n), dunno if baby monitors use that frequency or not. With the higher frequency you lose a lot of drywall penetration, so it's trickier to use. I think there's a 900Mhz one as well (cordless phones used to use it), but I think it's pretty small and not all that useful for data or baby monitors.

--Ian
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Old 01-18-2016, 07:13 AM   #18
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Quote:
Originally Posted by mgeoffriau View Post
lulz at negs for wanting to keep an eye on my 8 month old.
Lulz at multiple negs for thinking it's not necessary.

EVERY parent is over protective at first. It's only natural to be that way. By the second kid, or a couple years in, you're much less so. Companies capitalize on that worry, selling padded this and that and all sorts of safety crap. BTW, don't get the cabinet locks. They are a pain, and the kid figures them out by age 2 anyway.

Kids are amazingly tough - if you let them, they can shake off what would leave an adult prone in bed for a day. As long as you don't shake the **** out of them, they can handle quite a bit.
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Old 01-18-2016, 10:14 AM   #19
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Quote:
Originally Posted by rleete View Post
Lulz at multiple negs for thinking it's not necessary.

EVERY parent is over protective at first. It's only natural to be that way. By the second kid, or a couple years in, you're much less so. Companies capitalize on that worry, selling padded this and that and all sorts of safety crap. BTW, don't get the cabinet locks. They are a pain, and the kid figures them out by age 2 anyway.

Kids are amazingly tough - if you let them, they can shake off what would leave an adult prone in bed for a day. As long as you don't shake the **** out of them, they can handle quite a bit.
I considered a detailed reply about why I considered your comment to be insensitive, ill-considered, and off-topic, but this'll do:

If your kids have faced no serious health issues in their lives, I'm very happy for you. Not everyone has enjoyed the same experience.
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Old 01-18-2016, 11:24 AM   #20
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Quote:
Originally Posted by codrus View Post
There is also a 5GHz unlicensed band (used for 802.11n), dunno if baby monitors use that frequency or not. With the higher frequency you lose a lot of drywall penetration, so it's trickier to use. I think there's a 900Mhz one as well (cordless phones used to use it), but I think it's pretty small and not all that useful for data or baby monitors.
Chiming in with some technical data from Title 47 CFR part 15...

Yes, the 2.4 Ghz band is currently quite popular, for the very reason that it overlaps WiFi. This lets manufacturers use RF components which, because they are also used in WiFi devices, are extremely inexpensive, widely available, small, and efficient. While creating WiFi interference is not the primary intent, the choice of this band in newer devices based on its commonality with WiFi is a deliberate one.

The 900 Mhz band (actually 820-930, with some breaks in between) is also quite popular, though I'm not sure who is using it these days. This is where analog cell-phones and cordless home phones live, so there's actually a huge amount (relatively speaking) of available bandwidth here. While these devices are mostly obsolete, I'm pretty sure the band is still reserved for their use. Devices in this range will not interfere with WiFi.

Going back in time a bit, 27 Mhz and 46-49 Mhz are also popular bands, as this is where cheap remote-control toys and older analog cordless phones operated.



That having been said, Cuban women pronounce WiFi as "we fee." Don't believe me? Try it.
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