Radio module choices

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#1
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Hi All -

I'm looking into using a set of radio transceivers at one point, but don't know much about them (yet). This would be for pretty simple serial transmission of data from a PC to an AVR.

There are lots of choices out there ...

First one is probably what frequency/format to use. I've seen some cheap and small Laipac ones that can use 315MHz, 413MHz and 434MHz. Then there are some at 915MHz, and others up in the 2.4GHz range.

I would expect the 2.4GHz ones to have a little trouble in a typical home. That's a pretty common freq for cordless phones, though 5.8GHz is becoming more common. Also 802.11x wireless access points use the same range I think. Wouldn't there be interference ?

How about the lower freqs ? Which of those would you recommend ? What are the pros/cons to each ?

Dean 94TT
"Life is just one damn thing after another" Elbert Hubbard (1856 - 1915)

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Sparkfun sells some very nice modules. I'm using the HAC-UM96 in an ongoing project. It's a 433MHz 9600baud bidirectional serial RF link that is quoted for 500m range. Users on the forums there have quoted much larger ranges though. From all the reports I've heard it works terrifically. Tomorrow I plan on giving it it's first test run.

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[North America] The ISM bands do not require a licence although there are regulations. You could experiment in those spectrums and have a viable commercial product at the end if that is your intent. Cell phones can pollute the UHF bands.
2.4G is interesting. It works better than it should inside a building. But there are so many variables that is it hard to guarantee a quality of service. Many systems adapt their throughput according to signal quality.
It would be good to specify your data rate (two way, multicast?), range, topology reliability, budget (money), OEM or custom design, protocol stack, etc. Then you will get better answers from people here who know more than me and have a life too :-)

In a non-technical evaluation 2.4G radios are small (sub credit card size), low profile, sexy technology :-) and offer Mb data rates. Sweet at a price! ...if you need it.

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I just met with the VP of Marketing from Radiotronix last week. Looks like they have some nice data radios. They have serial versions as well as less expensive versions where you do the protocol work. Mouser carries their radios as well as many other distributors.

-Tom

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This is a comparison a company did of two of it's products that differ only in the spectrum they use (900 vs 2.4Ghz) 900mhz win for reliablity/range though is more susceptable to pager interference. Aso since so many cordless phones have switched over to 2.4ghz already the 900mhz spectrum is a LOT cleaner than it used to be.

http://www.maxstream.net/support...

-Curiosity may have killed the cat
-But that's why they have nine lives

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Quote:
I would expect the 2.4GHz ones to have a little trouble in a typical home

...and microwave oven mess the transmission.

Regards
heguli

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This is for a simple point to point link, from a Linux server (via serial) to a remote wall-mount display. Low data rate (20-30 chars/sec or so) and one way only, distance only about 20-30m. In a small corporate environment, so probably no microwave ovens, or at least not all the time aside from an occasional office one.

Everyone has cordless phones these days, both at home and in the office, so I'm leaning to the 915MHz and 315/413/434MHz versions. Any advantages (or cons) for one over the other ?

Sparkfun is a cool site - lots of neat toys. Will be visiting there more, definitely.

Dean 94TT
"Life is just one damn thing after another" Elbert Hubbard (1856 - 1915)

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Most of the frequencies you quote are for Europe, as far as I know only 914MHz and 2,4GHz (and higher) are allowed license free in USA. I certainly recommend you avoid 2.4Ghz. Range is much less per watt and too many other users around. In Europe I use 433MHz modules and get 450m range at 10mW. My source is MK Consultants (www.mkconsultants.co.uk) who are cheaper than others in UKand very friendly. Mohammed will give you bags of advice. I think he has agents in USA. He has some FM modules that give 1.5km (a mile to Yankees!).
You can see my medical pagers at www.itsdesigns.co.uk