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Can PC read 433MHz radio signal?

Posted on 2013-10-28
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Last Modified: 2013-10-30
I have a "weather centre".  It comprises two units.  One - outdoor - is a rain and temperature gauge.  The other - indoor - displays a clock and indoor temperature plus the external temperature and rainfall.  Communication between them is wireless on, the manual says, "433.9MHz +- 250KHz".  The "open field" range is stated to be 100 metres.  The actual distance between outdoor and indoor units is about 20 metres and, despite thick walls, reception is fine.

My questions are:

would it be possible to pick up the transmissions from the outdoor unit directly on my PC?  That is located a similar distance from the outdoor unit.

If it might be possible, what sort of hardware/software would I need on my PC to do that?

Roger
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Question by:Sancler
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by:Dave Baldwin
ID: 39606527
You would need the radio receiver that is built in to the indoor unit and interface circuits to convert the radio signal to something the computer could understand.  There are weather stations that have computer interfaces built into them.  Maybe there is a module for your unit that will do that.
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by:Bird Dog
ID: 39606642
Might be easier and cheaper to buy one that already does what you want something like the following. I have never tried the following I am just using it as an example
http://www.acurite.com/environment/aculink-compatible.html?features_weather_stations=100
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by:Sancler
ID: 39607374
Dave Baldwin

"You would need the radio receiver that is built into the indoor unit ..."  You appear to be saying that it is ONLY THAT SPECIFIC RECEIVER that can receive signals sent on the frequency specified.  Is that correct?  What I was hoping was that there were other (cheap) generic receiver/s with computer interfaces that would do that part of the job.  Is that not the case?

I realise that the signal, if I can capture it, will need interpreting.  But if it can be represented on my PC in any readable form (which is why I asked about software as well as hardware) I reckon I stand a fair chance of identifying those bits of it in which I am interested.  I have, after all, the display on the internal unit to compare with any captured results.

Both

Thanks.

I know there are commercially available weather stations that do link to computers.  But, being time-rich and cash-poor, and a hobby programmer, I wanted to see what I could do myself once I'd cracked the reception bit.

Roger
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by:Dave Baldwin
ID: 39607391
Technically you don't need that exact receiver... but I've never heard of generic radio receivers with a computer interface.  There's no market for them that I know of.
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by:Bird Dog
ID: 39607404
the following are build your own you may be able to adapt from there
http://www.instructables.com/id/Wireless-outdoor-Arduino-weather-station-with-PC-l/
http://www.toptal.com/c/how-i-made-a-fully-functional-arduino-weather-station-for-300

I just google build your own weather station that connects to a computer
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by:Sancler
ID: 39608321
Sorry.  I seem to have given the impression that I was asking about weather stations.  My mention of the rain gauge was, however, only intended to put my question into some sort of context.  My question is more general than that.

I know that there is a radio signal, of sufficient strength to reach my PC, which is being transmitted on or about 433MHz.  I know that my PC can receive radio signals.  In some cases this is via my wireless router but that is on 20/40MHz.  In other cases (e.g. wireless keyboard and mouse) via a USB plug-in.  I don't know what range that works in, but it's obviously dedicated hardware and software.

I also know, in general terms, that there are scanners/receivers that interface with PCs.  For instance Googling has thrown up, in the UK, "EzTv645 DVB-T DAB DAB+ FM USB SDR Dongle RTL2832U/FC0013".  From my position of relative ignorance on radio matters, that looks to cover the bandwidth I am interested in.  That's the cheapest I could find but there are others costing not much more.

What I was hoping to get from my question was two things.

First, assuming that I am right that something like that would receive the signal I am interested in, is there readily available software to convert that radio signal into data, rather than sound/tv, so that I can analyse it?  If so, what should I look for?

Second, are there any recommendations for hardware "something like that".

Roger
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Expert Comment

by:Dave Baldwin
ID: 39609491
I know that my PC can receive radio signals.
Not without additional hardware.  And unless you are trying to receive signals from some common application that does have affordable commercial products, you are pretty much stuck with expensive laboratory grade equipment.  And there are many methods of putting a signal or data on a radio carrier.  And there are many ways of encoding that data.  It may even be encrypted which will make deciphering it quite difficult.

Since you have decided not to tell us what you are actually wanting to do, it is hard to help any better than that.  It may just remain your 'secret'.
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by:Sancler
ID: 39609600
There is no secret about what I am trying to do.  I am trying to see if I can get my PC also to receive directly the signal which is transmitted by my outdoor unit and currently received only by the indoor unit which came with the rain gauge.  And if I can get the PC to receive that signal then to see if I can identify that part of the signal which identifies when the rain gauge collector clicks over (which happens after a few millimetres of rain have been collected) so that I can record rainfall against a much finer time scale than the display on the indoor unit allows.  It also gets the data (in that finer form) to where it ultimately ends up (in its broader form) without me having to type it in to my PC from the display on the indoor unit.

If I find that rain gauge data that is transmitted no more than 100 metres is indeed encrypted then I might not be able to do it.  But my guess is that that is unlikely.  And I only reach that stage if I can receive the data and analyse it.  That is a risk I am prepared to take.

I have researched enough to think that reception might be possible with something like the dongle I mentioned before and analysis with something like SDR#.  But I admit virtually total ignorance in radio stuff, so thought it worth asking the Experts.

If it is genuinely not possible, then I would prefer to be told that rather than spending money and time on a wild goose chase.  But I would like to understand why it is not possible in the light of the thinking I have outlined above.  Will a dongle like that not receive the signal at all?  Will the software available not allow me to parse the signal into bit-based data?

Roger
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Accepted Solution

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Dave Baldwin earned 500 total points
ID: 39609702
The rain gauge data is unlikely to be encrypted.  The EZTV645 USB DVB-T DAB FM Digital TV Tuner Receiver Stick http://www.amazon.com/Patazon-EZTV645-Digital-Receiver-Latest/dp/B009DCHTRI may be able to receive the 433MHz signal but it will try to output MPEG encoded video for digital TV.

You might take a look at some of the other NooElec products on that page that say SDR Software Defined Radio.  You would have to get the software that goes with them to see if they would do what you want.  http://www.nooelec.com/store/
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by:Sancler
ID: 39612128
Thanks.  

Sorry for the delay in coming back but I've been researching the market.  

I've found an SDR dongle which is programmable to "a device mode in which raw samples can be captured and transferred to a host computer".  If I've understood that correctly it should allow me to inspect the bitstream precisely as it was transmitted by the rain gauge, rather than having to battle through "MPEG encoded video for digital TV" (which I suspect might have involved data loss, even if I could crack it).

I'd already looked at nooelec but, being based in the UK, hoped I could find something local.  And I did.

I'll close this now and ask again if (or more likely when) I hit snags after the stuff has arrived.

Roger
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Author Closing Comment

by:Sancler
ID: 39612139
Thanks for sticking with it.  I feel more confident now that it's worth spending a bit to follow my ideas up.
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Expert Comment

by:Dave Baldwin
ID: 39612211
You're welcome, good luck with your project.
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