Equipment test: Alfa Signal Amplifier Booster

The gear needed for wardriving

13 posts • Page 1 of 1
Having become frustrated in my quest for a better mobile antenna, I decided in a fit of desperation to give an Alfa Signal Amplifier Booster (http://www.data-alliance.net/servlet/-s ... SMA/Detail) a try.

CAVEAT: Please note that the web page above SPECIFICALLY states that this is not for use with USB wireless adapters and using it with one might burn out both pieces of equipment. The specs/details tab on that page also warns that it shouldn't be used with an omni antenna (despite the fact that it comes with one). So don't do this at home, kids, unless you're willing to lose 60USD worth of electronics. You have been warned. I will not accept responsibility if you emulate my foolhardiness.

Ignoring all warnings, I have found in static tests that this thing does provide about a 10dbi signal boost. I did not fry anything during the few minutes I tested it, despite being one room away from my boosted wifi router (I like to live dangerously). I hope to test it out on the road and on my test course soon.

One downside is that it runs on household current, and I haven't found a car power adapter that works with it yet, so I'm going to have to run it and my netbook off a power inverter.
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I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
Interesting. The page shows that it comes with an AC/DC adapter. What is the DC output? And what is the reasoning for the warnings?
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AC/DC Power adapter included: DC 6.0V x 500mA, AC 110 ~ 240V Power Adaptor

Apparently customers were burning out their electronics: http://support.data-alliance.net/wifi-signal-booster/

I took it on a run tonight and things seem to be OK so far; unfortunately file parsing is stuck at the moment so it's hard to judge the results.

The biggest problem I'm having so far is that my netbook doesn't like the power my inverter is feeding it and refuses to charge off of it.
Image

I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
My problem with finding a car power adapter is finding one with the right size jack, the port on the booster is very small. Is there any kind of standardization to these things?

Taking a quick look at my kismet logs, the packet counts seem to be off on the boosted card; some of the unboosted cards actually saw more packets. And there don't seem to be many APs that were seen exclusively by the boosted card as I would expect from a range increase.

On the other hand, at the site where I usually start my run, I usually see 50 to 70 APs at startup; today the count was up to 112.
Image

I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
Aaaaaaaand I just burnt out my card on my test course. An Alfa AWUS036H dies a noble death in the name of science. Listen to your ol' uncle bigs, kids, and _DEFINITELY_ don't try this one at home.
Image

I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
Upon further review, I have discovered that I did NOT burn out my wifi card, but rather that my new linux installation was not configured correctly. Naturally, I discovered this after I purchased a replacement. Someday I will learn to alter one variable at a time.

So, further tests will be conducted as time permits.
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I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
Just curious about your continued research/use of these amps? Is it making a difference? Can you see a consistent improvement in your ability to pick up APs with it? Which cards are you using this with?

Thanks!
OK, I have some data.

Same course, same night, two runs with an Alfa AWUS036H.

With the amplifier: 1006 networks seen.

WITHOUT the amplifier: 1036 networks seen.

So, as far as wardriving is concerned, I'm going to have to rate this little doohickey as: Not Worth the Bother.
Image

I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
Plus, I broke the little bastard unscrewing my card from it. Only solder joins the RP-SMA connector to the device. Very shoddy.
Image

I've been outside the box. There's a bigger box.

Give a man a fish, and you feed him for a day. Teach a man to fish, and eventually you will run out of fish.
Thanks for that information. I think I will avoid that particular model, at least for the time being.

I've made some tweaks to my 2.4GHz rig. I used giskismet to load everything into one, cumulative SQLite database, and I did some queries to analyze channel usage data. Looking at my 120k or so APs, the results were very telling. Something like 97% of APs I've seen have been on 1, 6 or 11. As a result, I reconfigured my (4 AWUS036H card) 2.4Ghz rig, so that one card stays on 1, one on 6, one on 11, and the fourth hops among the other channels.

If the size of my gpsxml files and/or my AP density along my routes is any indication, I would say that little rig is EXTREMELY effective now.

I think there is room for LOTS of improvement on the 5Ghz side, though. The 51 cards only cover a subset of the 5GHz spectrum.
... giskismet ...
OMFG you are my number one hero in life; I SO needed that pointer! My homebrew SQL implementation has not scaled well.
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No problem. Glad I could help. Yea, giskismet just crams everything into SQLite, and you can access the data by using 'sqlite3 wireless.dbl'

At some point, I'd like to import all of my stuff into Postgres.
My excitement was in seeing a piece of PERL code parsing .netxml files. My own solution to this point has been perl parsing .nettxt into MySQL, but I'm not a very good programmer so it's taken more work than I'd like to get everything parsed, correlated and indexed correctly.

If you're dreaming of Postgres, you might like dreaming of PostGIS (postgresql gis), because then you could submit SQL queries like "show me 400APs within 1KM of this location", and "show me the intersection of these three APs"!


Sorry for the thread hijack, I've always been suspicious of 'cost effective' amplifiers - even with RX gain they add noise... You might get good results with a HAM style 13cm pre-amp (or a vintage MMDS preamp like ccie4526 claims to use), but a "quality" preamp in HAM land is like $400. Maybe cost-effective could help if you added some quality receive filtering to keep out-of-band cellular signals away but those are expensive also.

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