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Osairas
01-20-2010, 10:41 PM
I need a Tx-Rx whose Tx transmits a simple sine wave (if square wave is there then it is better) and at receiver i receive same sine wave only upto 1meter range. after 1 meter it must either amplitude decrease or nothing com at o/p. i found a ASK module from Vega kit is it useful? details are in attachment which im attaching pls reply me i need it greatly me

docel
01-21-2010, 02:55 AM
It is not possible at 1m.
You are looking at what is called as RSSI ( Received Signal Strength Indicator). It is a part of many Superhetrodyne receivers, not the cheap TRF / regenerative Rx usually sold at around 200 to Rs. 400 in India.
Your datasheet does not specify the model so dont know the RX chip-set. If it is a PLL based RX, then it must have an AGC out put pin. This can be used to derive the Signal strength.
To get a signal strength @ 1m
1. you'll have to put the entire RX inside a metal box, with a hole in it.
2. Reduce the Transmission power to 50 - 100uW. The best way is to put the TX too inside a metal box with a hole.
3. Tap the AGC voltage and feed to an op-amp, rectify the o/p and drive a VU meter etc.,
4. There is no way you can restrict an RF transmission to 1m. due to near field propagation.
5. The best way to do this @1m is to make a low freq transmitter, around the AF band, and use mutual coupling technique with air as the Permeable media.
in simple words- make an Audio Freq transmitter , put a coil as the antenna, place another antenna attached to a coil at the reciever. This constitutes an Audio transformer with Air as the coupling media.

It will be better if you can specify what you need this for and why. Makes things easier to answer.....