does the GSM system require a mobile phone sim card and a contract ?
Yes.
can bluetooth be boosted so the tx is high power ?
No. AFIK, there are no Bluetooth devices with the sort of range you are looking for. Long range for bluetooth is 100m. Normally bluetooth is intended to be very short range e.g 10m
BTW. I forgot to ask. Does this system need to be legal?
Use of high power transmitters on ISM band e.g. possibly the one you linked to, is not legal in most countries as it interferes with everyone else using the same ISM band.
i.e the device you linked to is a simple AM (OOK) and will be on 433.92Mhz, like every other wireless door bell, wireless thermometer, wireless power meter etc etc in your area, so could disrupt their operation
the device will be used on a race track so i guess it will get a lot of engine noise and could interfere with normal rf devices ( imagine every doorbell going off for 2km ! )
the xbee looks like a very nice solution some of them are quite powerful
is the xbee a secure method of transmission ? can somebody snoop on the data being transmitted ?
i only need the transmitter to be powerful - the rx will only receive data - can you mix a weak and a powerful xbee ?
basically i want to transmit rpm g force and speed
Like putting a rubber band in place of a chain link. Yes, you can do that, but why would you? If the "powerful" has a range of 2 miles and the "weak" one has a range of 12 feet, then when used together the range is 12 feet.
is the xbee a secure method of transmission ? can somebody snoop on the data being transmitted ?
Relatively, yes. And probably. But, if you are using API mode, then it could be challenging to make sense of the data. If you use AT mode, you can encrypt and decrypt the data using whatever methods you like.
basically i want to transmit rpm g force and speed
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can you mix a weak and a powerful xbee ?
Like putting a rubber band in place of a chain link. Yes, you can do that, but why would you? If the "powerful" has a range of 2 miles and the "weak" one has a range of 12 feet, then when used together the range is 12 feet.
can an xbee operate in tx mode only so it does not need to find the rx before it transmits ?
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is the xbee a secure method of transmission ? can somebody snoop on the data being transmitted ?
Relatively, yes. And probably. But, if you are using API mode, then it could be challenging to make sense of the data. If you use AT mode, you can encrypt and decrypt the data using whatever methods you like.
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basically i want to transmit rpm g force and speed
And this needs to be secure? Paranoid?
the information could be very valuable to a competitor !!
the information could be very valuable to a competitor !!
If they stole your car, too. Knowing what g-forces your car is encountering/resisting seems useless information without knowing HOW you are managing that.
Knowing what RPM you are at? How is that useful?
There are many ways to get the speed of a car on a track. You can hardly expect to keep that a secret.
can an xbee operate in tx mode only so it does not need to find the rx before it transmits ?
No. Point to point XBees need to associate before they can transmit. The transmitter (car) needs to be able to transmit to the receiver (pits?), and the receiver (pits?) needs to be able to transmit to the transmitter (car).
the information could be very valuable to a competitor !!
If they stole your car, too. Knowing what g-forces your car is encountering/resisting seems useless information without knowing HOW you are managing that.
Knowing what RPM you are at? How is that useful?
There are many ways to get the speed of a car on a track. You can hardly expect to keep that a secret.
the information is not for a car - you could be able to go and look at the tyres and then work out which ones give the best g forces from the data ! the revs min and max together with the lap times and track location will let a competitor know which gear ratios work best
Gadget999:
is the xbee a secure method of transmission ? can somebody snoop on the data being transmitted ?
XBees can do 128-bit AES encryption. For details, XBee product manuals can be downloaded from digi.com and there are probably other resources like application notes there as well.
i only need the transmitter to be powerful - the rx will only receive data - can you mix a weak and a powerful xbee ?
Even if the data flow at the application level is one-way, the modules still communicate in two directions in order to send acknowledgements and other network overhead. As others have noted, mismatched modules will work, but range will be limited to that of the lower power module.