Can I ask some expert advice to select radio modems to be used in a small
UAV (a model airplane infact) ?
Desired specs for the radio modem;
o Range : 5km (or more)
o Weight : Lighter than 150gm
o Data rate: 56-115.2K bits/sec
o Interface : RS232 (and/or TTL)
o Price : Must satisfy budget constraints of five uni students (ie. as
low cost as possible)

<Jeff Rina> schreef in bericht
news:43a80b79$0$18197$afc38c87@news.optusnet.com.a u...
I am not an expert on the matter,
but have some teaching on aviation
and the use of radio comm's therein.

have you any idea of the preferred carrier frequency?
VHF (80-150 or so MHz) offers good reliability
but is line of sight, i.e .will not follow the earth's curvature

at a very rough estimate, 5 kms range
would require 400 ft flying altitude -
dos that sound reasonable?

though I have received tower comm's at /- 10 kms distance
quite clearly, with a simple receiver,
and neither tranmitter nor receiver applying high antenna structures

final tip: i remember seeing some projects
of R/C aircraft with a camera and transmitter installed
so as to monitor the camera image on the ground
let google be your friend!

Have a look at sparkfun.com - they have some nice cellular modules that
look like they might work pretty well for you. They also have two lower
speed rf modules, um96 and um12, that have very good range (which will
improve very much when in the air). Best of luck,

M. Noone

JeffRina wrote:

In article <43a80b79$0$18197$afc38c87@news.optusnet.com.au> , <Jeff Rina>
says...
The 9Xtend series from MaxStream may fit your requirements. The
modules are about $299. ( you wil need 2, of course). I'm in the
early stages of evaluating a system that uses these modems, so I
can't tell you much about their ease of use and reliability.

Mark Borgerson

<Jeff Rina> wrote in message
news:43a80b79$0$18197$afc38c87@news.optusnet.com.a u...

Think we have been here before. See:
http://groups.google.com/group/aus.e...491f7d43e2dc30

Unfortunately the top of the thread contains some childish crap, but later
some info.

Regards,
Richard

http://www.FreeRTOS.org

try www.maxstream.net

I've personally tested their Xtend modules to more than 75 miles.

Standard Dipole on the airborne end, a small dish on the ground.

Test was terminated at 75 miles because that was as far as we needed and
I could not legally climb any higher, without oxygen, to maintain a clear line of sigt
over a mountain ridge where we were testing.

I've tested their raidos to over 20 miles with dipoles on both ends and no gain.

These tests seem to be somewahat sensitive to the population density in the area,
7 miles was my max measured range on the ground in the San Diego area.

Be aware that they are line of sight and you must respect the freznel (spelling?) zone limits.


Paul







On Wed, 21 Dec 2005 00:47:29 +1100, <Jeff Rina> wrote:

On Wed, 21 Dec 2005 00:47:29 +1100, <Jeff Rina> wrote:

I really hope that you do not intend to send the flight control
commands over any toy radio modem operating in a license free band.
Such links are vulnerable to interference from other users on the band
and these radio modems usually operate in half duplex, with
unpredictable latencies.

I would suggest using a separate R/C command system for flying the
plane that operates in a band dedicated for R/C activities and use a
separate radio modem for telemetry downlink. In this way the links can
operate independently in full duplex mode.

When selecting the downlink radio modem, you should also check if it
is allowed to use airborne transmitters in a license free band (such
as 2,45 GHz).

Paul

I recently did buy some radiometrix module transceivers 64kbs half duplex
for 20?



<Jeff Rina> wrote in message
news:43a80b79$0$18197$afc38c87@news.optusnet.com.a u...