How would I go about getting data over distances of 5km+ ? The situation is open cut mining. There is no cellphone coverage and we’re dealing with mobile machines, so directional antennas can’t be used. I don’t mind if I only have 50 bits per second.
Is there any way to do this with off the shelf hardware? (ISM band, legal)
what’s your budget??
google for “long distance data rf modem”. lots of companies. not cheap, I would hazard a guess…
I once looked at implementing a very long range system with amateur radio equipment. My plan was to use handheld radios along with encoders/decoders. There are many plans available on the Internets. Should be very doable, except you’d need to be certified if you’re in the USA.
Do you have line-of-sight? If so, it seems like it shouldn’t be too hard. You could maybe even use a non-ISM-band radio if you can get rights to some unused spectrum — in cities, there are lots of commercial allocations for taxi dispatch or whatever, and I’m guessing those frequencies aren’t in use in your mine.
Other crazy idea would be to build a mesh-routed network out of, say, 500-meter transceivers, which could pass messages along. This would let you transmit around corners and stuff. OTOH, you’d have to place and maintain all those repeaters (and program them to mesh-network usefully…)
Budget is somewhat less than the 100k or so it takes to get a new design type approved I’m limited to ISM band, legal power. It should be possible to go a very long way on 10mW. The problem is, the makers of data modems seem to be in a competition to see who can provide the highest bit rate, rather than the longest range. And yeah I’m aware of the difficulty of conventional designs with increasingly narrow bandwidth… But if they can get a GPS signal to travel 20,000km (50bps) with a few watts…
My half baked ideas center around using a regular transceiver and simply retransmitting the same bit pattern and using statistics. The problem here is you need a very basic radio - no framing, error correction etc. Anyone want to suggest a suitable chip? Problem is the ones I’ve seen that let you do your own modulation, tend to be low end affairs… very low power… poor frequency control… ASK etc.
As for meshing. Yeah, I’m still going to have to do that anyhow. The best radio modem that I can find, that uses the 433M ISM band is here on sparkfun. 1200bps… 1000M or so. And even then given my application there may still be unreachable nodes. We are talking very big sites
I should add… all the ‘long distance’ solutions Ive seen ultimately rely on yagis. Thats out of the question in this case. Sorry
I have seen a circuit that you can hook up the Nordic nRF2401 or nRF24L01 2.4 GHz transceiver chips up to a power amplifier chip (I think it was actually on the Nordic site). I know Atmel makes one of this type of chip. This is assuming you’d be willing to go in the DIY direction, though, and not off the shelf.
Russel, talk to Aerocomm or Maxstream. Maxstream claims the longest range, but I’ve heard from some datalogging frends to get a solid mile out of the Aerocomm modules with just quarter wave rubber duck antennas. Call the companies and ask to talk to tech support/engineering.
FWIW, you’ll have to talk to Maxstream to get a hand on their modems (I’ve never found them on an open market). Areocomm has Mouser for a distrubutor, and their “demo kit” looks nice at $200 (boards, antennas, carriers, serial connection to lap tops, power, etc).
You’re looking at probably 64kbps here, and I think they will slow down the data rate to increase sensitivity/range. 900MHz systems.
Yes, I’m aware of the Aerocomm and Maxstream units.
Only thing that bothers me about the Aerocomm is its protocol. So far I don’t have a detailed users guide so I can’t tell if it’s protocol is going to make things dead simple… or get in the way.
The Maxstream is really nice… and not cheap. I’m sort of hoping for for a competitor to pop up with something with reasonable sensitivity and bare bones access. (Yes I love my own protocols )
Having said all of the above, it’d still be nice for someone to come up with a unit that really does give you the ultimate range at low bitrates. There are lots of devices out there for which 50bps is plenty
Many of those on these boards live in the US I’m assuming. This unfortunately does affect a few things, especially our bands
I’ll give my thoughts on this
We have 900MHz and 434MHz (and 10% duty cycle there!) to play with generally. Other frequencies are restricted or require a license. I don’t know how much a “long range” commerical data radio would cost (with a few watts of output). Most of the hobbyist stuff I’ve seen that has range that you’re looking at are ham radio hardware, which may be a show stopper depending on the part of the world you’re in. Now, some designs may be modifiable to suit your needs (900MHz amplifier hardware attached to a ham packet radio transciver). Again, there may be power limitations for unlicensed hardware, I don’t know ISM guidelines well enough for this.
One big problem for you vs your examples of GPS is the radio spectrum itself. Nothing I know of transmits on the 1.5GHz band of GPS, plus they’re all somewhat directional antennas, so you can look skyward. They also often include some strong GPS and high quality low noise amplifiers. Now how does this work and keep it small? One, it’s a reciever, it doesn’t have to deal with switching between transmitting and recieving. Two, its specialized and high volume, so the manufacturers can greatly streamline their production to shrink size, weight, and cost.
You probably will run into regulation for this due to broadcast requirements. One suggestion, however. Ever consider trying to tie into some standard voice radios with an audio card via a headset jack? This is officially illegal for FRS/GMRS I believe (no data), but it might work with 900MHz analog voice radios.
My comment abouyt gps was purely to make the point that it’s possible to cover more distance if you’re prepared to restrict the data rate. And my main gripe about pre packaged radio modems is that they don’t do this. 
Have you looked at the “mote” and “sensor networks” people, like that group out of UC Berkeley? Maybe you could modify their design slightly to use larger nodes (with larger batteries and longer range).
I have Motorola P10 modules that operate in the 459 MHz business band. They are true NBFM, measure about 2"x3x.75" and put out around a watt of power. Truly old tech,I have used them very reliably over a 3 mile link at 2400 baud using a couple of FSK chips. They were FCC approved and built like battle ships. They can be tuned from 450 to 470 and are crystal controlled. $40.- each plus shipping. You can PM me if interested.
Ron
1W at 450-470Mhz isn’t legal here in Australia without a user license. So it’s not a contender. Out of curiosity, does it require a user license in the US?
Russel:
1W at 450-470Mhz isn’t legal here in Australia without a user license. So it’s not a contender. Out of curiosity, does it require a user license in the US?
You can get a commercial business license for a given unused frequency in the band. I have tuned them down to the amateur band for personal use with little loss in power or range. They were used for a PTZ remote control for a microwave video link by one client. The video antenna was right next to the P10 antenna with no discernable interference. I also have narrow band 172 MHz NBFM transmitter receiver pairs. The transmitter puts out 10 mW and I have detected the ID signal from 5 miles when playing with DFing. I don’t know what the 170 MHz band regs are for you down under…
Not to put too fine a point on it, but I presume the personal use was by a licensed radio amateur, either yourself or your client.RonnyM:
You can get a commercial business license for a given unused frequency in the band. I have tuned them down to the amateur band for personal use with little loss in power or range. They were used for a PTZ remote control for a microwave video link by one client.
I have been noticing posts on forums here and there that seem to convey that you can put up transmitters on the amateur bands to avoid having to get a license. Unless the FCC regulations have changed to allow unlicensed use of the amateur frequencies and now allow for commercial or broadcast use, then those transmitters are operating illegally.
(I presume the personal use was by a licensed radio amateur)
RonnyM:
(I presume the personal use was by a licensed radio amateur)
I was hoping that was the case!
Well just to clarify things, The context here is I’m asked to design something for a commecial product. It has to operate in an ISM band - unlicensed as far as the user is concerned, but not unregulated.
Which means limited bands, limited power and the user isn’t supposed to apply for a commercial license.
As much as I would love to get a chip and go for it, the regulators have decided to make it prohbitively expensive to get a device class licensed. Or what you guys would call FCC approved. Reason? A combination inflexible and prescriptive rules on the part of the regulations and a cosy little earner going on for the testing labs. I wasn’t joking when I said you need 100K or so to go through this process. So it’s pre built, pre approved modules I’m afraid.
And btw I do have some sympathy for the ameture operators. I’m not one myself but do have friend who are. The reason low power devices crept onto what was ameture bands was that the authorities in the first place didn’t have the foresight to create real dedicated bands for telemetry etc.
In any case the single biggest waste of spectrum is TV channels. It’s worse here in aus. We basically have 5 broadcast channels (infact some are still stuck in VHF, thanks to an earlier stuffup where they thought FM radio wasn’t viable). And yet we have dozens of channels. So much for the rant, back to where I started.
Shannon’s limit…
http://en.wikipedia.org/wiki/Shannon-Hartley_theorem
Now if you spin that around what you get is the range of a transmission is inversely propotional to the square root of the bit rate. So one quarter of the bitrate gives you double the range.
Of course this means building GPS like receivers where the very narrow band you’re looking for has to be hunted for in software. Well… I’d still love to see one
Btw I’ve pretty much settled on the Maxstream ZigBeePro which appears to be the exception to the rule of ZB being low power. These units have 60mW and claim 1.5km range. We’ll see
Probably. The ZPro is some microcontroller doing the hard stuff + a Motorola chipset. Motorola went a different route than many 802.15.4 chip makers and provided completely separate transmit and recieve lines, so it’s far easier to put an output booster into it.
Hmmm… I don’t know if you have any size requirements, but you might be able to boost power later, if need be, by using a consumer class 802.11x signal booster plus a moderate gain whip antenna (assuming you’re not too heavily 3D in radio placement requirements). I don’t know what power maximums are for ISM off the top of my head, though, especially for other countries.