Help-CRO picks up FM signal without any connection

I am doing a Wireless ECG. I get the ECG signal and I transmit it via FM. Once I input the ecg signal to the FM transmitter input the CRO automatically displays frequencies in MHz range even without any link/connection from the circuit to the CRO. The trace goes away when I remove the ground connection from the Fm transmitter and comes only when I connect the ground clip back to the transmitter ground! I am using a Transcend MP3 player as the FM receiver.
What could be wrong?

The input cable of the 'scope should be shielded.
Maybe you have a ground loop.

audioguru said:

The input cable of the 'scope should be shielded.
Maybe you have a ground loop.

Click to expand...

What do you exactly mean by shielding??

An audio and a video system uses shielded cable to eliminate interference.
The cable has a wire down the center and a braided or foil shield around it.