RF Modems

[donno]

Gooday folks,

Have been piecing together some idea's for  RF modems, basically the type you would use on remote sites to collect/send data.

Any knowledge base or other info available?

I guess the key is to keep it relatively simple, however distance between nodes must be around 1.5 to 2Kms or greater?

Will be using Microchip Flash device mpu's.

Cheers.

[frasenci]

Self made RF units will be tricky , I am not an Electronics men could not help.
We have tried out several US$ 5-12 RF kits ( Rx + Tx ) , but NEVER got good results ( probably lack of expertise on my side ,..... )

But I have succesfully made applications with Bluetooth units for PIC based, on Field Data Aquisition, systems. Very simple to put together , uses straigth Serial Out RS-232 transmision. This will put you in a 50 m range . ( We designed based on the fact that the operator had to visit the DAQ stations capturing accumulated data with a Bluetooth equiped Pocket Pc. ( IPAQ ).
These ones also succesfully used to establish an telemetry Downlink for RC Helicopter Models ( Sends Rotor RPM and Engine Temperature every 1 Seconds )
Bluetooth radios are very stable I have confirmed. Rc-Pilot monitoring his machine on flying field with an NoteBook.....

Look here

Code:

http://www.sparkfun.com/commerce/categories.php?cPath=16_115

No experience on these others but looks interesting , will put you in the 1000 m Range , also RS-232 based , should be also very simple to implement .

Look here

Code:

http://www.sparkfun.com/commerce/categories.php?cPath=16_113

Thre are manufacturers for more power equipment ( same principle ) , I used to have the links when I did my research , dont have them any more , you will have to google a little. ( This ones Industrial rade )

I remember I read also about using cheap Motorola Walkie-Talkie like radios to establish this type of RF links .

Finally , have a look at

Code:

www.parallax.com

, they used to offer an ( high priced ) modem unit....

Hope this helps.

Greetings