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toozie21

Looking for low-cost RF module recommendations

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I am currently playing with a nifty little module from Anaren called AIR (2pg pdf:http://www.anaren.com/sites/default/files/Part-Datasheets/A1101R09C.pdf), for a low-power embedded project and it works OK; but I was wondering if anyone else had experience with any other like type modules?

My loose requirements are that I would like to reasonably (not pie-in-the-sky) hit 1/4 - 1/2 mile distances at slow speeds (9600 baud is fine). I would like to use an omni antenna (so no high directional antennas), would prefer the module to have pre-FCC approval, and would like the modules to be less than $15. Lower the power draw the better, but we know how that trade-off works!

Those requirements really limit me, but the Anaren part seems like it could cover them; I am just curious what other things are out there that I might have missed. I am not married to the 900MHz spectrum, it just seemed like the most likely place for me to meet my goals. This is for an outdoor transmission.

 

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@@toozie21

There is the Nordic nRF24L01+ RF you could try. The CC2500 and the Nordic NRF24 are the two radios people have used in this forum. There is another CC radio someone posted for long range, I cannot find it.

 

Edit: Found it: CC112x >25Km range.

Also.. new member, welcome to 43oh!

Edited by bluehash
Welcome wagon.

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Sure, drop me a note.  As a general rule, most of the long range stuff is going to get you in trouble unless you really know what you are doing.  There are a lot of networks out there, all over the spectrum, and when some technician notices abnormal packet loss... they will find you :smile:

 

You can avoid trouble by staying within FCC or ERC (or whatever) regulations you need to deal with.  In USA, it is a bit more difficult to achieve long range with with CC112x (say, > 1km) than it is in Europe.  In US 915 MHz band you will need something more robust than a Launchpad G-series MCU to do the DSSS.  The Semtech LoRa parts have an internal codec that does that for you, so they may be worth a look.  With a launchpad an CCxxxx parts, the easiest way to get longish-range in the USA is to use 433 MHz at -3dBm and a low data rate.

 

Another nice thing about 433 MHz is that you can build a pretty amazing directional antenna with just a coat hanger bent roughly into a circle -- might need some tuning though.  If you are more of a perfectionist, you can wrap a copper tube around a 30cm (1ft) diameter bucket and get the same thing.  I am completely swamped with work until July, but maybe I'll do an instructable in the summer on that.

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Thanks for having me, someone over on the dangerousprototypes forum turned me onto this site.

 

I appreciate the help. I am in the US and definitely want to play nice with the FCC. What modules to you recommend in the 433MHz range? Anaren has one, but it only has EU approval for some reason.

 

That would be a pretty good instructable!

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Thanks for having me, someone over on the dangerousprototypes forum turned me onto this site.

 

I appreciate the help. I am in the US and definitely want to play nice with the FCC. What modules to you recommend in the 433MHz range? Anaren has one, but it only has EU approval for some reason.

 

That would be a pretty good instructable!

About Anaren.. I had a poject at work and the client wanted to go Anaren, as the modules were FCC approved. However we were working with the audio radios. Had an antenna and all on the module.

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About Anaren.. I had a poject at work and the client wanted to go Anaren, as the modules were FCC approved. However we were working with the audio radios. Had an antenna and all on the module.

The first set of module I had of Anaren's had that built in loop antenna on the PCB.  I carefully laid out the board to accommodate it per their recommendations, but the range on it really was sub-par in my opinion (good enough to do some stuff in a house though if that was all you needed).  If I stick with anaren, I will need to throw an omni onto there.

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The first set of module I had of Anaren's had that built in loop antenna on the PCB.  I carefully laid out the board to accommodate it per their recommendations, but the range on it really was sub-par in my opinion (good enough to do some stuff in a house though if that was all you needed).  If I stick with anaren, I will need to throw an omni onto there.

I'd also like to add that the audio radios had an LNA or amplifer. Once enabled, range almost trippled. Without it, it was nothing.

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Yeah, I was pretty disappointed with the range, but the price and FCC approval is pretty sweet. Not much else out there that I saw (hence the post) that hit the price point and had approval though.....

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Welcome to 43oh forum, I figured you would get some response.

 

Curious to know if anyone has ever been tracked down for exceeding EIRP in a ISM band. Just seems to me to be very difficult to track down. Then again I do not live in a very urban/high tech area.

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I appreciate the help. I am in the US and definitely want to play nice with the FCC. What modules to you recommend in the 433MHz range? Anaren has one, but it only has EU approval for some reason.

Any module that claims FCC approval is only doing half the job, but half the job is better than no job at all.  Both FCC and ERC have duty cycle limitation in most license-free bands, and complying with that is largely application dependent.  So, even if you have an FCC approved module in your product, the product itself must go through FCC testing anyway before it goes to market.

 

The US 433 MHz band is very restrictive and difficult to design into a module.  On the plus side, because it is restrictive it is much more clear than US 915 MHz band, which is a mess in a lot of places.  If you are doing some event-driven communication, 433 is a safe choice, you are probably not going to get in trouble.

 

The HopeRF modules are the traditional el-cheapo 433 MHz modules.  Some of the higher-end ones use Semtech silicon, or possibly chinese copies of Semtech silicon -- who knows.  The SX1231 is a high performance transceiver on-par with the CC112x units.

 

Welcome to 43oh forum, I figured you would get some response. Curious to know if anyone has ever been tracked down for exceeding EIRP in a ISM band. Just seems to me to be very difficult to track down. Then again I do not live in a very urban/high tech area.

 

If I were to blast 915 MHz from my apartment, the effect would be that the smart-meters in my area would drop a lot of packets because they are in the same band.  The energy company would eventually come to the bottom of it.  HAM operators, though, are usually the biggest pains in the ass for ISM operators.  They have access to 433 and 915 MHz bands, and they listen. 

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Any module that claims FCC approval is only doing half the job, but half the job is better than no job at all.  Both FCC and ERC have duty cycle limitation in most license-free bands, and complying with that is largely application dependent.  So, even if you have an FCC approved module in your product, the product itself must go through FCC testing anyway before it goes to market.

 

The US 433 MHz band is very restrictive and difficult to design into a module.  On the plus side, because it is restrictive it is much more clear than US 915 MHz band, which is a mess in a lot of places.  If you are doing some event-driven communication, 433 is a safe choice, you are probably not going to get in trouble.

 

Ah, you are right.  I had done a bunch of research on this about a year and a half ago and forgot that that was one of the reasons I abandoned the 433MHz process.  You got me thinking about it again and I totally glossed over that stuff.  I had actually wrote Anaren on Saturday to see why they didn't have FCC pre-certification for their 433MHz AIR parts (like they do for their 915MHz), and this was their response (hint: it plays RIGHT into what you were saying):

Unfortunately, the FCC no longer grants modular certification to 433 MHz transceiver modules such as ours because they do not contain a processor and software that can guarantee compliance with the strict regulations placed on the 433 MHz band.  So the decision is out of our hands.

 

We did do the testing on the module to see that given the right software it can operate within their requirements.  But any product that incorporates our 433 MHz module would have to go through FCC testing to achieve certification.

 

In my case, it won't be event driven in the pure sense, it will be reporting in on a set time interval.  So if I remember correctly, it didn't seem to keep with the essence of what the FCC wanted to see in that band.  

 

So in the end, I guess that gets me back into the 915MHz band, right?

 

<<An aside>>

I got that Anaren response on the same day (Saturday) and when I asked it.  The couple of times I wanted clarification or some more information from them that isn't in the datasheet, they have been very responsive and accommodating.  I've been highly impressed.

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In my case, it won't be event driven in the pure sense, it will be reporting in on a set time interval.  So if I remember correctly, it didn't seem to keep with the essence of what the FCC wanted to see in that band.  

 

So in the end, I guess that gets me back into the 915MHz band, right?

The usual trick to turn a times-driven sensor into an event-driven sensor is to transmit only the deltas.  That is, in a temperature sensor example you would transmit a report when the temperature changes by some amount.

 

The advantages of 915 are:

- 26 MHz allocated as 13x2 MHz channels in 902-928

- much better propagation than at 2.45 GHz (i.e. range and especially going through walls, trees)

- allows up to 1W transmission, although this requires signal spreading.

- possible to build reasonably compact antenna at this frequency

 

The disadvantages are:

- only available in USA & Canada

- much worse propagation than 433 & 169 bands

- high transmission power allowance leads to unwanted, unpredictable wideband interference

- LTE now interferes with this band

 

If you have a spectrum analyzer, and SDR of some kind, or even something like the CC430 "spectrum analyzer" kit, you can look at the spectrum analyzer and find the most open channels, then use those.

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I am currently playing with a nifty little module from Anaren called AIR (2pg pdf:http://www.anaren.com/sites/default/files/Part-Datasheets/A1101R09C.pdf), for a low-power embedded project and it works OK; but I was wondering if anyone else had experience with any other like type modules?

 

My loose requirements are that I would like to reasonably (not pie-in-the-sky) hit 1/4 - 1/2 mile distances at slow speeds (9600 baud is fine). I would like to use an omni antenna (so no high directional antennas), would prefer the module to have pre-FCC approval, and would like the modules to be less than $15. Lower the power draw the better, but we know how that trade-off works!

 

Those requirements really limit me, but the Anaren part seems like it could cover them; I am just curious what other things are out there that I might have missed. I am not married to the 900MHz spectrum, it just seemed like the most likely place for me to meet my goals. This is for an outdoor transmission.

 

How about Synapse Wireless modules?

 

The SM200 is about $16 in quantities of 500 (Digikey Pricing).

 

Does that catch your interest?

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