In Reply to: pls clarify my doubt on AM RC system. i m having oral presentation soon posted by janet on 02/22/03 at 1:49 PM:
I am not going to solve this problem for you, you have to do some work yourself. However, I do have some input for you:
1. The bandwidth depends on the design. In general the narrower the bandwidth the better for reduced noise and interference.
2. AM is simpler to implement, although FM is not that complicated.
3. Ordinary AM is used, any thing else is too complex.
4. I don't know how they work, but the simple Radio Shack toy cars probably do not use any thing as sophicated as digital coding. I expect the transmitter has multple frequencies for the NE555 and the receiver has multiple NE567 PLLs to filter the received signal.
5. I could do this, but you will not learn that way. Use a Google search for the items and match up what you find with the schematic. BTW there is no LPF in the transmitter.
6. If you use insulated wire, the insulation will provide spacing. Or, if you wind two wires and remove one, that will leave a space.
7. See #5
8. You can have multiple frequencies in the NE555 by changing one of the capacitors. Look up the data sheet to find out which one. You will need multiple NE567 in the receiver because of the need for seperate outputs.
9. The attenuation in water increases with frequency. The U. S. Navy communicates with submarines using frequencies near 10kHz.