The file should be a zip. Just checked the link I sent you and I'm just seeing it's a*.bin file. You could try the one from the link forwarded by BWolf although this appears to be for CWM.
After this, you may also want to see if you won't be better off going to full stock 4.3. I'm not sure the hybrid firmware (4.1.1 ROM with 4.3 Bootloader/Modem) offers any real benefits.
Here's a TWRP flashable zip for the modem if the CWM doesn't work.