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

[Michael Noone]

"RST Engineering \(jw\)" <jim@rstengineering.com> wrote in
news:116q7gro32jo2f8@corp.supernews.com:

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




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.

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

 

[RST Engineering (jw)]

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

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

 

[Michael Noone]

"RST Engineering \(jw\)" <jim@rstengineering.com> wrote in
news:116q9fogi1l0225@corp.supernews.com:

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

This is the aircraft: http://www.bergenrc.com/Intrepid60.asp. 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

 

[Frithiof Andreas Jensen]

"Rene Tschaggelar" <none@none.net> wrote in message
news:426bc08d$0$1148$5402220f@news.sunrise.ch...

The legal version would be a mobile phone, eg GPRS.

.... 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.).