Long range, low bitrate, small data transceiver unit for telemetry data

Satellite phones :-)

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++++++++++++++++++++++++++++++++++++++++++ Jenal Communications Manufacturers and Suppliers of HF Selcall P O Box 1108, Morley, Western Australia Tel: +61 8 9370 5533 Fax +61 8 9467 6146 Web Site: Contact: ++++++++++++++++++++++++++++++++++++++++++

"Leo Patrick"

** Sure - long as they are installed onboard a space craft.

Try asking NASA.

......... Phil

wireless ap and decent directional dishs

Would a GSM/GPRS cell phone data module work?

See

They work great where ever you have cell phone coverage. The data charges can add up if you have to move a lot of data. The costs are low for low data rate applications. $25/month (Canadian dollars) gives us

256KB/month which means about 8KB/day. The more data you sign up for, the lower the cost per byte. Check with your GSM cell phone provider.

The hardware is reasonable priced and the developer's kit is inexpensive. The dev kit even includes a power supply with power cords for most countries except Australia.

Actually, that raises an interesting question - I know various applications including buoys, wild animal research collars, etc. use a satellite uplink to communicate GPS data and other telemetry to home base.

Who does one contact about buying bytes on a bird like this? I'd be interested to find out what it costs to set up this sort of thing.

A general search on argos satellite applications will yield lots of results.

Mark Borgerson

EXTREMELY interesting, thanks for the link! One transmission a day on a floating platform is about $77 per month, which gives you position data plus 256 bits of telemetry.

There is a clause in there about not being able to get bird time if there is a commercial equivalent to Argos, though. I wonder what commercial equivalents there are... hmm, more research necessary.

There are some devices that are good for 10Km, but probably not much more... see

Ken

10 km would be quite optimistic for those devices.

The sensitivity is specified at -120 dBm, which is about the same as specified for NBFM radio telephones in the VHF range. These have typically 1-5 W of transmitter power and in portable operation with their own antenna, a few km of reliable coverage would be expected.

The original poster is apparently in Australia, so the 0,1 W output power for the Radiometrix module could be used, however, in Europe, only 0.01 W transmitter power could be used, thus reducing the range even further.

To realistically reach the 10 km distance, the other station would have to be high up in a cellular or water tower or alternatively, at both ends of the link, the antenna would have to be above the tree tops or on top of the buildings in urban areas.

If the system is intended for export, it should be noted that the regulations for various radio transmitting devices varies considerably, including allowed frequency bands, power levels, acceptance tests etc. for licensed and license exempt devices.

I would suggest using GPRS if it is available in the area.

Paul

Have a look at

- the modems will do 20-30 km depending on terrain and antennas, battery life would depend how much you want to transmit.

Tom

Yes, we make them. We put GPS engines on collars and transmit the data over RF. In order to get the kind of range you're looking for, you have to have special transmitters and receivers and nice conditions. For example, our Osprey model has 150dB gain. It's a small (one-handed), water-resistant, battery-powered receiver. We get 50 miles / 80km with ideal conditions with a good antenna.

If people, mountains, rain, animals, trees, rocks, buildings, cars, etc are in the LOS, you'll get reductions in range.

As for batteries, there are lead-acid batteries and there are Lithium cells. How much weight can you afford?

How much data do you want to send? Beyond certain thresholds - which are very small - the data can get corrupted very easily. Small amounts of data (10-50 bytes) work very well.

Someone else mentioned Argos - we have our own Argos PTT, and we do sell them seperately and/or to third parties. Trust me, you do not repeat NOT want to make one yourself.

--
Magnus McElroy
Electrical Engineer (EIT)
HABIT Research
http://www.habitresearch.com
(250) 381-9425

Thank you very much for the "Argos" link. I have found it very interesting. Following link from the Argos' web site provides a list of transmitter manufacturer for the Argos system

My intented implementation in the original posting/question is a semi-controlled baloon. Because of the very limited weight carrying capability of the baloon, we can not carry big, high power transceivers. Transmitters for the Argos' system could be very small (as light weight as

7gram t be carried on a bird . But because our implementation requires two way communication and we do not have the oportunity to wait the next pass of the Argos' satellites over Australia, unfortunatelly Argos system does not seems to be applicable in our case.

So I'm still looking for * Long range (10-100km) * Low bitrate (1200-19200 baud) * Small * Battery operated * radio transceiver units to send/receive digital data to be used between a semi-controlled baloon and a ground station for telemetry and control application.

Why didn't you say that in the first place ?

It makes *ALL* the difference if the stations are down in the ground clutter of if you have a free line-of-sight path.

So apparently you only have the weight restrictions on the balloon system, not on the ground system?

Do you have power restrictions on the ground system ?

Could you use directional tracking antennas on the ground ?

With such applications, I would suggest that you stay away from the license free bands and get a dedicated frequency (pair) with a sufficient power limit (say 1-100 W) for the ground transmitter from your telecom authorities.

For the control functions, you might even consider systems intended for model aircraft control and use a completely separate system for telemetry downlink on a different frequency band and thus be able to continuously communicate in both directions. You might even set up multiple telemetry receiving stations on the ground at different locations.

Paul

"Paul Keinanen" "Leo Patrick"

** Don't get too excited just yet - there are still heaps of important details the OP has not revealed about his app. ** At 100 km range, that damn balloon better be up in the stratosphere for a free line of sight ! ** With a Tx weighing in at circa 7 gm all up @ 100 km range plus hovering barely on the horizon, the OP will need access to the Parkes radio telescope dish ! ** Needs plenty of watts on the up link plus massive gain with a tracking dish for the down link. ** Or just get NASA to help out.

They could help the OP with his spelling too.

........... Phil

Theoretically, you only need to be at 625 m altitude to get the 100 km radio horizon, in which the attenuation is only slightly larger than direct line of sight. From a plane flying at 10 km, the whole island of Cyprus (about 150 km long) fits nicely into a singe view.

A 100 km troposcatter path not very hard with directional antennas and moderate transmitter power.

Paul

"Paul Keinanen" "Phil Allison"

** Over water that is about the *visible* horizon from 625m - providing there are no waves at all.

BUT for a CLEAR line of sight over terrain that may include ground levels thousands of feet above sea level - my comment stands.

** That 100 km diameter mill pond is damn hard to find.

** 10 km altitude IS in the stratosphere, depending on one's latitude.

The OP likely wants his 100 km range to extend right down to local ground level - to maintain remote control.

** How lovely and vague.

And useless and smartarse.

............. Phil

These people would seem to have trod the same path already

Anyone would be forgiven for thinking you have a monopoly on RF technology. You get nasty when Paul confronts your good story with actual facts based on such wishy washy crap like geometry and real world observations. Sounds like you want him to go away and stop undermining your "AWW-thorra-TAY".

kind regards Mark

Not actually - the ICAO standard formula for radio horizon distance is

d = 1.23 * sqrt(altitude)

where d is in NM (nautical miles, 1852 m) and altitude in feet (0.3048 m)

This gives 1927 ft (587 m) above terrain for 100 km.

Please note that the distance is larger than obtained from direct geometric consideration. This is due to the refraction of electromagnetic radiation in the atmosphere.

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Tauno Voipio
tauno voipio (at) iki fi