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XBee strength weak
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XBee strength weak

by grantg55 on Sat Nov 27, 2010 6:36 pm

Hello,
I have a XBee project I am working on, and I'm suspicious of my XBee's signal strength.

Nothing will get through past 25 feet line of sight in my house (testing in a hallway).

Around 22 feet the RSSI is -88 - -96. I put them right next to each other (1.5 feet apart) and it only goes to about -70.

I am suspicious of my power supply. I cut up an old cell phone charger (4.8v, .9a) to use going through ladyada's XBee adapter. The coordinator XBee is using the FTDI cable from adafruit (usb power). Im a beginner, so If you see any errors/problems let me know! thanks.

I realize im in an urban environment, but just 25 feet line of sight down my hallway seems...weak. Maybe it is normal. If it is, I'll make it work but otherwise I'd love to boost it.

Lastly, I'm using the XBee sold in the adafruit shop.

Thanks for any help!
Grant
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Re: XBee strength weak

by stinkbutt on Sat Nov 27, 2010 7:02 pm

Are you in a high-rise apartment building? The more urban of an environment you are, and the taller the building you're in, the more likely you are to be running into METAL in the walls, which will act like a Faraday Cage, (think that wire cage Gene Hackman had in Enemy of the State.)
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Re: XBee strength weak

by grantg55 on Sun Nov 28, 2010 5:57 pm

Nope, im in the suburbs. As far as i know, my house has no more metal in its walls than the next house does. I do have a question though supposing I did have metal walls. Wouldn't the faraday cage only create problems if there were a metal wall blocking the 2 XBees? I was getting those results when they were in direct line of sight of each other.

Sorry I don't know much about this topic (radio waves)

Thanks for the reply,
Grant
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Re: XBee strength weak

by stinkbutt on Sun Nov 28, 2010 6:03 pm

grantg55 wrote:Nope, im in the suburbs. As far as i know, my house has no more metal in its walls than the next house does. I do have a question though supposing I did have metal walls. Wouldn't the faraday cage only create problems if there were a metal wall blocking the 2 XBees?


It's not that simple. The presence of metal in the signal path attenuates the signal, and yes, has to be in the path, but there's not just one path. A radio signal with take a zillion different paths, ranging from the direct a-to-b path to bouncing off walls and around corners. Anything that is conductive is going to attenuate that signal, because E and B is = 0 inside of a conductor.

Now that actually means conductors also make excellent reflectors, (which is why the reflective surface of any mirror is a - wait for it - a METAL,) but it just complicates the problem. I was asking you from the thousand-mile-high perspective - "Got a lot of metal in your walls?"

Sadly, that's the length and breadth of my expertise on radio.
Red M&M, Blue M&M: They all wind up the same color

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Re: XBee strength weak

by richms on Sun Nov 28, 2010 7:34 pm

Which antennas do you have on the xbees? Only asking because I saw someone online had ones with the socket on them and was complaining about low range and they didnt have any antennas connected to them.

Also, have you changed the power level in XCTU at all?

Tried changing them both to another channel? Someone nearby may have one of those aweful analog video senders or cameras, and they seem to be the worst at killing the performance of other stuff since they are a constant transmission.

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Please be positive and constructive with your questions and comments.