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

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

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- 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

Reply to
Michael Noone
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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

Reply to
RST Engineering (jw)

Chineese spider-skimmer WiFi? ;-)

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--
  Keith
Reply to
keith

I don't think it's really possible legally, in most countries. Unless you are willing to accept a largish dish antenna at the ground station. Are you in the US, as indicated?

Reply to
Ian Stirling

Ian Stirling wrote in news:426bbd3e$0$42311$ snipped-for-privacy@ptn-nntp-reader02.plus.net:

I forgot to bring this up. Aren't you allowed to use more power if you have a ham license? I'd be willing to go through the training if that was needed. And yes, sorry, I am in the US. How large of a dish antenna are you thinking of? It would probabaly be fine.

-Michael

Reply to
Michael Noone

Rene Tschaggelar wrote in news:426bc08d$0$1148$ snipped-for-privacy@news.sunrise.ch:

This would mean having to sign up for a cellular plan, would it not? Is there any way to communicate mobile phone to mobile phone? In some of the areas where this needs to work I expect there will be little to no cell coverage.

-Michael

Reply to
Michael Noone

The legal version would be a mobile phone, eg GPRS. Unless you intend to operate in remote areas, a mobile phone is also the cheapest. as you don't have any infrastructure cost.

Rene

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Reply to
Rene Tschaggelar

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

Hi Jim - this will not be used for commercial purposes. It's for a university sponsored aerial robotics club. Our club is working on a completely autonomous aerial vehicle, and we need a way to remotely monitor it, and in the case of system failure, control it. I should mention that the vehicle will be moving, so a directional antenna system would be less than ideal. It's also possible that the vehicle will spend some time between buildings, so any way to keep a data link with line of sight obstacles would be awesome.

-Michael J. Noone

Reply to
Michael Noone

keith wrote in news: snipped-for-privacy@att.bizzzz:

Only problem is I expect that is highly directional, and our vehicle will be quite mobile, so that would cause some serios problems.

-M. Noone

Reply to
Michael Noone

Well, there was that smiley in there (see: ;-). I read the mobile/omnidirectional requirements later. I thought the Chineese WiFi stuff cooked though.

--
  Keith
Reply to
keith

Does your university have an amateur radio club? If so, contact that club, and ask them for assistance.

--
Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  
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Reply to
Peter Bennett

I read in sci.electronics.design that Michael Noone wrote (in ) about 'Solutions for long range (3-5KM) RF communication?', on Sun, 24 Apr 2005:

Is the original 27 MHz radio-control band still available? Being on the borderline between HF and VHF, it may be more suitable where there are obstructive buildings. Obviously, you want a re-tuned high-efficiency CB antenna at the ground base.

--
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
Reply to
John Woodgate

John Woodgate wrote in news: snipped-for-privacy@jmwa.demon.co.uk:

Hi - is 27MHz what is used for normal hobbyist RC equipment? If so - eventually we will not be using that band, but at the moment we are.

-M. Noone

Reply to
Michael Noone

I read in sci.electronics.design that Michael Noone wrote (in ) about 'Solutions for long range (3-5KM) RF communication?', on Sun, 24 Apr 2005:

It WAS; I suppose it still is in some countries.

Why refuse to use it if it turns out to be the best one technically? You can use coded signals to prevent interference or unauthorized use.

--
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
Reply to
John Woodgate

You are kidding, no? With all the obscenity, power mikes, and "power boosters" on the Children's Band you think the FCC is going to bust some kid transmitting a half a watt of data? Surely you jest.

On the other hand, because of the length of a decent antenna at 27 MHz., I'd suggest that the original poster look at the ham bands, especially those right around 1 GHz. THe local ham club (see

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for a list of those near you) will be most happy to help you. The license to use these frequencies involves getting a C on an exam no more difficult than a freshman watered-down electronics class.

You did say that you wanted bidirectional data, didn't you? That complexes up the issue a bit.

Jim

Reply to
RST Engineering (jw)

I didn't read anything about tall buildings (or single bounds, or Superman) in the original post. Maybe I just missed it. What I saw was a ground station and an airborne station with a 2 mile range requirement for bidirectional data. Perhaps the original poster would be so kind as to set the WHOLE DAMNED PROBLEM out at once so we don't piecemeal the answer.

Jim

Reply to
RST Engineering (jw)

Because it may not be legal to use it in such a manner. I thought that the FCC prohibited data transmission in most bands.

Reply to
Ian Stirling

Well, that DOES pose a bit of a problem...10 meters in the air is about 30'. Radio horizon (in miles) is given by sqrt (2*h) where h is the altitude in feet. Max range is therefore somewhere around 8 miles (15 km) so that doesn't seem to be a problem. What **is** a problem that John caught is that you need to do this snaking around buildings, and that really cobs the works up.

Yes, as John noted, the lower the frequency that you can use the better, so

27 MHz. may in fact be your band of choice. I'd have to go back to see if there is a data band in either 20 or 40 meters, but again, you are getting into the area of antenna size tradeoff.

How big is this aircraft and what is the weight limitation on the complete setup including a power source (probably batteries).

Jim

Reply to
RST Engineering (jw)

For radio-control, you are allowed ONLY to transmit data, nothing else.

--
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
Reply to
John Woodgate

John Woodgate wrote in news:OlhHx8En $ snipped-for-privacy@jmwa.demon.co.uk:

So you mean modern RC equipment no longer uses this band?

I think I spoke (wrote) unclearly. What I meant is that currently we have an RC backup system on board in case of system failure. Eventually we'd like to completely ditch that system, but right now we still do have it, and it is still necessary.

-Michael

Reply to
Michael Noone

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