Hi - I need to establish a bi-directional data link between a ground station and an aerial vehicle. Distance should be at most 3KM and should be in a relatively flat area, but there is the possibility that there will be buildings in the way, so the stronger the signal the better. As far as data rate goes, 10KBps would be great, but a lesser data rate would be OK as well. The ground station will have plenty of power available to it, but the aerial vehicle will have a much more limited power supply, so the less power it uses the better. Another limiting factor is weight and size - really the smaller the better when it comes to weight/size. Ideally I'd like to come up with something the size of an altoids tin.I have been looking at the Nordic Semiconductor nRF905() - I have been told that it has a good range, but I have never heard numbers, and I don't know how to translate specs to numbers (ie how to go from mw or db to meters). Could anybody explain that to me? Or if it is fairly complicated - point me to a good resource on the topic? Obviously - I am no expert when it comes to RF. I have also looked at some RF chips made by Linx Technologies, though the Nordic chips are much more attractive (besides the awful QFN 32L package)So - does anybody have any suggestions as to good RF solutions for this application? Thanks so much for your time!Michael J. Noone

DIsh antennas? 5 km range? Have we REALLY forgotten how to do VHF link communication? Good grief, a hundred milliwatts into a dipole at both ends will easily do 5 km.You can use a kilowatt if you are an amateur radio operator, but why bother. A micropower 2-meter rig at the aircraft end and a decent 2 meter FM rig on the ground will be overkill. The only caveat is that you canNOT use it for commercial purposes. If the intent of your communications is without monetary interest, ham frequencies can easily be used. If you are collecting the data to certify some product for commercial purposes, you can't use amateur radio.There are DOZENS of legit ways to get data air to ground. Exactly what are you trying to do?Jim

Solutions for long range (3-5KM) RF communication?

Apr 24, 2005 23 Replies

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Michael Noone 21 years ago

"RST Engineering \(jw\)" wrote in news: snipped-for-privacy@corp.supernews.com:

I'm sorry I wasn't more clear. The vehicle should theoretically never be more than about 3KM away from the base station. If something goes wrong it could venture farther, so the longer the range the better (though I'd be rally surprised if it went as far as 4km away from the base station - that would mean something had gone very wrong). It will always be fairly low to the ground, - maybe 100 meters in the air at most, probabaly normally more like 10. It will have to navigate around some buildings, so it will not always have line of sight to the base station. My apologies for not being clear enough.

-Michael J. Noone

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John Woodgate 21 years ago

I read in sci.electronics.design that "RST Engineering (jw)" wrote (in ) about 'Solutions for long range (3-5KM) RF communication?', on Mon, 25 Apr 2005:

But he's got a bad shadowing problem due to tall buildings. I'm not even sure that a lower frequency than 27 MHz might not be better.

Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

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Michael Noone 21 years ago

"RST Engineering \\(jw\\)" wrote in news: snipped-for-privacy@corp.supernews.com:

This is the aircraft:

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Current power source is some sort of 12V battery which is being shared with a low power computer. I've been told the vehicle can carry something along the lines of

15 pounds. I expect the current equipment onboard weighs somewhere along the line of 5-8.

Thanks again,

-Michael J. Noone

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Frithiof Andreas Jensen 21 years ago

.... Maybe Not:

Using a mobile terminal in an aerial vehicle *may well* be illegal - it messes up the network because the mobile will cover many more cells than the network was designed for so you will be soaking up more ressources than planned (i.e. a DOS attack ;-)

The unlicensed WiFi IEEE 811.x.x, e.t.c. do not carry such limitations. WiFi will travel a very long way with a decent antenna (but directional, l.o.s.).

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