Long range communication

[Christopher4187]

Hi everyone,

Does anyone know of a module or device that I can use to send data from a PIC at a range of about a mile or so. I currently use Linx chips but the range is about 3000 feet and I need a little more then 5000 feet. FCC certification is not a problem but something that is relatively easy to use would be good!

Thanks,

Chris

[Steve_88]

Hi Chris,

Not my area, but have you looked at what MaxStream has to offer?
http://www.digi.com/products/wireless/

-Steve

[duncan303]

Hi Chris

As Steve suggested Maxstrem I thought I might add a little ramble

I have used xbee and xbeepro, they can work out the box, I had them up and running very quickly,couple of hours.
you should get 5000 feet out of the pro version (caveat. as long as it is not in a lead lined box). You can easily mesh them round obstacles, I remember initially running into trouble with the interface from maxstream it is a bit quirky.
If you change the speed of comms between the units for gods sake write something on the unit to tell you what you have done, I have one unit nailed to the wall its associate pin flashing away happily on its own network, I am completely unable to reprogram it and the units do not have an external flash restore to factory settings feature so beware. I am hoping one day that my rogue device will latch onto something nearby so that it will feel it has a purpose in life, I have nearly given it a name. I feel unable to turn off it's life support!!

Also watch out for maximum supply voltage Vdd do not exceed 3.5V ever, but the data pins are TTL tolerant so you can hook them up to a 5V device.

I have found that the chip antennas are slightly better than the whip

do you get the feeling I like them, there are loads and loads of settings that you can alter,which make the units very versatile, however this does require quite a lot of reading, so make sure you have the correct datasheet manual.

I personally prefer to print my manuals and datasheets out in their entirety. I use treasury tags to hold the whole manual together but staple each section as one. The reason I said this is that I initially printed out and prepared the wrong version of the zigbee protocol product manual.

Oh yes, the pitch of the pins, these are a total pain and the only downside to an otherwise great unit, I never solder them directly but use cut down single row header strip mounted on prepared PCB. you are going to have serious difficulty using these on a breadboard..... beware. If it wasnt for the pin pitch I could have had them going before I took them out the box!.

Duncan

[Christopher4187]

Thanks for the reply Duncan. I have a few questions for you.

You say the chip antenna is better then the whip, why? Does the chip antenna get a longer range?

Were you able to achieve 5000 feet with ease or was that on a flat field with no obstructions?

Did the orientation of your unit matter for reliable communication?

Did you find that lower baud rates were more reliable for communication or did that not matter?

Thanks,

Chris

[duncan303]

Hi Chris,

Well I have really let myself in for it now!
I am not an RF guy.. lets face it they are gods men amongst mortals, gurus of the mystical black art of EMC, the closest I get is not having seen a razor or daylight for 10 years! I remember just enough wave theory to be dangerous……… I mean really dangerous both to myself and to others

You say the chip antenna is better then the whip, why? Does the chip antenna get a longer range?

I did say the chip antenna was better than the whip, this was a totally incorrect statement, I have no quantifiable analysis data to back that up, quite the contrary.

Did the orientation of your unit matter for reliable communication?

When I last reviewed this component I swapped to the chip antenna for two reasons the first being that it was more compact in the enclosure and the second was that studying the range distribution graphs, which I think I obtained from maxstream, of the different units the chip antenna gave a more even distribution, for me that was more effective in that they required less consideration to installation.

If anybody is running an anti-electrosmog campaign then I suggest you look away now.
If there is an area within your “theatre of operations” that is a bit “dark”. Then simply hook one of these puppies up set it to the mesh network and chuck it in. its as simple as adding an extra stock cube to a casserole.

Did you find that lower baud rates were more reliable for communication or did that not matter?

To be honest I have not really tried to assess any maximum speed/conditions. Its Zigbee. I can send an array 64bytes as a string with hser 19200 PIC to PIC no problem at all, the units are almost invisible in that respect, you can set the number of retries for each packet sent, along with loads of other setting to tweak. For me I want the data to arrive, zigbee is pretty industrial and thus designed to be reliable. You send it and it will get there.


Good PCB practice is worth a mention, I treat an xbee circuit and its footprint as I would analogue in layout terms, Henry W Ott as a reference book, classic. He’s from round your way, Whippany? Sadly though I suspect he is no longer with us.

Anyway on to long range communication the actual subject of your original post, It really depends are you looking commericial?

If you are not and into a bit of fun then read on.

Some years ago some bright spark thought it would be a good idea if all us Europeans got together and became “one”, well in principle that may sound great but it seems they neglected to notice we all speak completely different languages, anyway they choose a town to place this new parliament in, somewhere called Brusseles I could not place it but I guess it is in the exact geographic centre of the “union”, because they would not be able to agree on anywhere else! oh and they gave us a new currency called the euro, If I went down the local shop they wouldn’t know what to do with it, its hard enough trying to pay with a Scottish pound round these parts. Anyway Brussels, it seems as if there are 30 multilingual interpreters for every parliamentarian all crammed into this swanky new building, anyway the point is that there is loads and loads of money chucked at it to make it work and they award some as grants, the awards of these grants does not to appear to work on meritocracy but to whoever has the patience and fortitude to succeed in filling in the correct forms. Nobody appears to understand what the proposals are about but if you use the word “rural” you get 1 more point.
So anyway somebody managed to get a few million of our quids(ukpounds) to go round sticking a mesh network, supposedly offering free internet access, to most of our street lamposts, somewhere that had the least interest and lowest population. They didn’t have enough money left for advertising (good job), but was left to people in the know and people like me who viewed these strange “transmitters” with curiosity to find out what was going on. So I got my binoculars out and managed to trace the manufacturers. At first I thought they were air-monitoring devices but they informed me it was the “Norfolk Openlink Project” . great I thought this sounds fun so off I went the Council offices, bit like Brussels but without the interpreters, The Norfolk Openlink what? They said.

Time is running short so the point is that this was indeed free internet access the only problem being that you had to be physically underneath a transmitter lampost to actually log on. I tell you sharing a lampost with a couple of confused migratory birds in the nightime with a laptop on batteries, trying to log on to this PICBASIC forum just shows the lengths that some of us will go to.

Anyway moving on……. First I modified a WOK with USB wireless stick. Mounted in the focus using a hot glue gun and some barbecue sticks, later on though I built myself a cantenna out of empty tins etc having further modified the USB wireless stick. Exactly the same method I used could be done with one of these whip antenna xbees. From hardly one lampost I was accessing up to 20 from the same spot. Little bit of understanding of a standing wave captured into a tilted tin can provided me with loads of fun, not least lurking about large metal containers in the supermarket with a tape measure, my callipers and a calculator. I was finally rumbled at home when I brought back a giant tin of pet food and was caught.

Ok so some people watch television at night I don’t, I choose to play instead although I do get bored quite quickly, I noticed today that they have increased the size of the antennae on the lampost units but I haven’t looked to see if it made any difference, the project is about to end very soon anyway. So no doubt somebody will go round taking back the transmitters paid for by Brussels and sell them on as “field tested” grade one.

Anyway Chris if this is your thing then take a look at “cantenna” there is also a “figure of 8” that is reputed to perform well, in fact some claims for cantenna are pretty impressive, add to that the reliability factor of zigbee and you could be up and away.

Duncan

[Christopher4187]

Duncan,

Thanks for the extensive history lesson. This reminds me of a story where a student in college (not sure if this is true or not) has a final exam where the teacher simply put "why" on the chalk board. Most students wrote tons of pages on "why" but this one student just wrote "because" on his sheet of paper and turned it in. Maybe he got an "A?"


Anyway, I think I will just order the development kit and play with it. They seem to be pretty easy to use so I guess I will just have to see for myself.

I'm just curious though, what was the size of your PCB where you were able to achieve 5000 feet?

Thanks,

Chris

[Ron Marcus]

Another contender in the race for space is Radiotronix. I have been using their WI232FHSS-250 modules at 900 MHz with great success. The link software is a breeze to set up, and it does have factory default reset on power up if necessary. So far, I have gotten 2 miles LOS with little stubby antennas. You can transmit at up to 115K baud and the units can be configured for auto retransmit when no acknowledgement from the receiving unit. Just feed them serial, and get it at the receive end, right out of the box. I've been very happy with them.Available from Mouser.
Ron

[Christopher4187]

Wow, Radiotronix looks cheap, easy to use and seems to have the range I need. I'll try that one and see what it can do! Thanks for the information.

[Ron Marcus]

<<Ron Marcus has suggested radiometrix as well, Radiometrix is an RF guy he writes quality readable authorative articles over here in the UK on RF, hats off.
I really am wishing now I had not put my oar into this thread without properly reading the title.

Duncan>>

Hey Duncan,
Christopher got it right. It's Radiotronix, not Radiometrix. www.radiotronix.com
Ron

[duncan303]

Thanks Ron

Hey Duncan,
Christopher got it right. It's Radiotronix, not Radiometrix. www.radiotronix.com
Ron

really getting in a muddle with this thread