Seeking Radio Link Advice

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#1
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Hey all,

I just got a request to link stuff up by radio link and was wondering if anyone had first-hand experience with any add-on radio modules that do that kind of thing for you.

Basically the need is for low data rate communication - even 300 baud is plenty - that will work inside a building, through at least one concrete floor, and go about 600 feet.

Thoughts? Caveats? Things to watch out for? (the more subtle stuff - I think I have the obvious covered... or so I hope)

I have never done the radio link stuff so would like to stack the deck as far in my favor as I can.

Thanks in advance...

Please note - this post may not present all information available on a subject.

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Is it point-point, point-multipoint? Networking involved?

The concrete floor is likely to be a challenge. All that reinforcing steel in a grid makes a very good shield. You may need to go to a pretty high frequency (900MHz or higher).

There are some nice fully built RF modems for under $100US that might do the trick.

Try:

http://www.maxstream.net/
http://www.cirronet.com/
http://www.microhardcorp.com/

There are more....
Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Have had good success with the 900 Mhz Linx products. Easy to use
and not expensive.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Depending on the sales area, take in mind that as far as I know only 2.4 GHz (or higher) is accepted worldwide. Not 418 / 433 / 800 / ... MHz
I am now testing with Bluegiga Bluetooth modules

Patrick

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Thanks for the replies!

First off, no sales. This is strictly in-house use. And yep - networked - so they will need to monitor for collisions, errors in transmissions, etc.

I found a module at Linx yesterday that looks very promising as it is already FCC pre-approved and since getting FCC approval isn't really an option for this project (cost), that is the enabling detail to go wireless.

I'll look into the other links too.

Thanks!

Please note - this post may not present all information available on a subject.

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The links I posted all appear to be point-point modems.

If you are looking for a pre-certified device, then you will likely have to deal with networking at a higher level (that is, the protocol won't be built into the modem).

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Many CDMA solutions allow for networking in the way you describe. Bluetooth is one branch of CDMA, Qualcomm http://www.qualcomm.com/ are a major manufacturer of CDMA chipsets and have links to 3rd party vendors with modules for thier chipsets. You will need to check the maximum allowable distance that the device can transmit, and if power is a major consideration, standby and in use power consumption.

As the previous posters have noted 2.4Ghz is the only worldwide frequency band that is currently accepted (as far as I know). However, 2.4Ghz is also a harmonic of the microwave oven, and for this reason one major telephone manufacturer I know of switched back to 900Mhz.

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I have used the Maxstream modules, and I am happy with them. They can work networked.

Regards,
Alejandro.
http://www.ocam.cl