Long range, low bitrate, small data transceiver unit for telemetry data - Page 3

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



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Would a GSM/GPRS cell phone data module work?

See http://www.multitech.com/PRODUCTS/Families/SocketModemGPRS /

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.

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


There are some devices that are good for 10Km, but probably not much
more...
see http://www.radiometrix.co.uk/products/bim1.htm

Ken
www.claymore-electronic.co.uk


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



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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


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


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    I suppose he could have his receiver up a tethered balloon
too to increase line of sight.

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


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Have a look at www.elprotech.com - the modems will do 20-30 km depending
on terrain and antennas, battery life would depend how much you want to
transmit.

Tom

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



Leo Patrick wrote:
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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)
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