getting radio signales

hi i have built this circuite and at the moment i am only using 2 of the inputes. But i get very heavy radio signales in the background . Do you now anything that i can do to stop me from getting rado signals.
and is the curved lines on the capcitores the negetive pole.

Thanks alot

Put this circuit in an iron box. Yes curved line is Ground = minus.

EMI

Even if you put the circuit into an "iron box" (an aluminum minibox or other such metallic shielded enclosure is sufficient), you might also want to add two capacitors in parallel from the +24v power supply input to ground. Make one cap a 10µF aluminum electrolytic and the other a 0.1µF disc ceramic capacitor. Be sure the positive end of the electrolytic is connected to the +24v. These two caps will be bypass caps that will knock down any RF signal entering through the power supply.

I sounds like you may have a power radio transmitter nearby.

By the way, putting this preamp into an aluminum enclosure would be a good practice, anyway, to keep any ac hum pickup or feedback to a minimum.

Dean