Hello Roy, try following tips: 1. Make sure the speaker grill and earphone jack are not covered by any obstacles. 2. Turn off the Bluetooth, Phone Noise Cancellation. 3. Reset.
Yup, as Chloe said, LCD was damaged, you can replace the LCD+touchscreen+frame, which can make your repair much easier and less risky, S3 screen replacement is not that expensive now, it costs less than $80, check it out: http://www.etradesupply.com/oem-samsung-galaxy-s-iii-s3-gt-i9300-lcd-screen-and-digitizer-assembly-with-front-housing-sapphire.html
I think it's the signal not hardware problem. Maybe you're staying too far away from the router. Anyway, if you want to replace your iPad antenna with a new one, here is the part: http://www.etradesupply.com/oem-apple-ipad-wifi-antenna.html