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Wireless Spectrum Analyzer on the Cheap
PennyManDeux writes "There's an article over at TheTechLounge looking at the Wi-Spy wireless spectrum analyzer. Here's a quote: 'Although most wireless boxes are able to push through the lower amounts of interference, some people, such as those living in apartments or otherwise deluged with many wireless signals may have problems. It is with this dilemma in mind that the people at MetaGeek created the Wi-Spy spectrum analyzer.' Cool thing is, it's only $100..."
Yes, it's under $100. That's news. But many other comparisons to the higher-priced analyzers aren't there.
1. Does it do channel characterizations? Apparently not.
2. Does it have channel reticules? Apparently not.
3. Does it do 802.11a? Apparently not.
4. Does it have enough resolution to find Bluetooth and other spread-spectrum devices? Apparenly not.
5. Can it identify specific kinds of interfering devices, like 2.4Ghz phones, microwaves, door openers, etc? Apparently not.
I say apparently not because none of this functionality, commonly found in other spectrum analyzers of this type, is even mentioned. It's nice to have a cool A-to-D converter in the 2.4Ghz region, but comparing this to Cognio or Air Magnet is like comparing a bicycle to a Porche. I can buy a bicycle for under $100. I can barely touch the ugliest old 914 Porche for $3K.
Don't be fooled by price, or comparisions that hardly scratch the surface of what diagnostic tools are all about. For under $100, it's pretty damn cute. But it's just the basics.... and minimalist basics at best.
---- Teach Peace. It's Cheaper Than War.
A link to the actual product page?
http://www.metageek.net/
You feel sleepy. Close your eyes. The opinions stated above are yours. You cannot imagine why you ever felt otherwise.
I'm not trying to justify the price of more expensive SAs. Instead, the article misses a lot of points and comparisons with the higher priced stuff, then baits the article with price so as to justify it. A good RF engineer could do his/her own fairly easily. The software that does the rest takes a helluva lot more. Basic FFTs are cute and a freaking high schooler ought to be able to do them.
This 'review', however, tries to make the comparison with higher priced equipment, then doesn't cite the features that makes that higher costing equipment compare to the under $100 variety-- only cost is used. Nice bait.... not very sharp hook.
---- Teach Peace. It's Cheaper Than War.
does it run with Linux?
Yes.
Yes, there are Linux and OSX applications available.
The linux app pretty much looks and works just like the Windows app, but it does have a raw output util that you can do some interesting things with.
I haven't used the OSX app, but the screenshots on their site look very good.
I'm against picketing, but I don't know how to show it.
I bought one of these...neat toy. The hardware is nothing special, it appears to be a Cypress WUSB reference design manufactured by Unigen. The firmware may have been modded a bit...if for no other reason than to change the USB strings (or not, I can't remember how it enumerates.) At any rate, I'm going to bet that they just look at RSSI across the band and report it back in a meaningful way. Clever use of the technology.
As many other readers point out, a spectrum analyzer it's not. I really don't think that's the intended purpose. It gives you an indication of band occupancy over time, and that's about it. For many uses that's just fine. If I'm trying to get some ISM-band device to form a link and it won't, the WiSpy gives a good first-order indication of band conditions. If WiSpy comes back clean, I move on to other diagnostic steps, generally involving test gear that costs (easily) 100 times what the WiSpy did. If it saves you some time, great. In my opinion, it's cheap insurance.
It's not a spectrum analyzer, but it is a nice panaramic receiver.
The difference between the two is resolution. A panaramic receiver is just
a band scanner. It will tell you what channels are occupied and the relative
signal strength. A spectrum analyzer will do the same and more, such as
giving you a good idea of the kind of signal you are looking at, and it's
purity. Many years ago Hams used panaramic receivers (scope display) to
see where the dx and band openings were without having to tune from one
end of the band to the other. If you are looking for a clear (or occupied)
channel the panaramic receiver is good enough. If you want to know why the
FCC cited you for a dirty signal, then you want a spectrum analyzer.
How about a USB extension lead and mount the whole device in the can?
I've done exactly this to yagi antennas to eliminate transmission line loss. The result is a thin USB wifi wand:
http://www.dattaway.org/antenna2.jpg
I'm a small office / home office IT consultant, and I bought one of these a few weeks ago after stumbling across it on ThinkGeek. It's fabulous for my needs, which are simple: figure out if interference is the reason someone's wireless network is flaky.
Wi-Spy does a great job of doing this. I fired it up at a downtown client and saw there was a strip of intense interference down in channel 1. Moved them up to 11- problem solved. I've also done some tests at home... it's very easy to tell the difference between a microwave, spread spectrum phone system, video sender, and other wifi networks... they have rather distinctive appearences in the graphs Wi-Spy produces. Now that I know what they look like, I can take an educated guess, where before, I was grasping at straws.
For those of you getting your panties in a wad about it not matching a $5000 spectrum analyzer: Duh? Of course it doesn't. But that doesn't mean it's useless... there are a lot of folks (like me) for whom the cost of a "real" spectrum analyzer is completely unjustifiable. But I can spend $100 easily, and *for what I do*, which is occasionally troubleshoot SOHO wireless networks, it provides most of the functionality I need.
The really interesting fact is that this thing defines an entirely new product category: inexpensive spectrum analyzers. I would really like to see what could be done for $500... that's still an order of magnitude cheaper than the existing solutions, but I bet you could add a bunch of features.
-R
A better review is available from Tom's Networking, including comparison to one of the $4000 Cognio devices:
i spy/
i spy/page2.html
http://www.tomsnetworking.com/2006/02/12/review_w
Comparison table on page 2:
http://www.tomsnetworking.com/2006/02/12/review_w
There is already a separate Linux app that has most of the functionality of the Windows app. I suggest using that versio (available from http://www.kismetwireless.net/wispy.shtml) instead of trying to get the Windows app running under Mono. The reason for this is that the USB library used by the Windows app, probably will not work under Mono.