1. The input requires jumpering as the input is a single line TTL input. The data arrives in NRZ format. I have checked this on the Oscilloscope and it works as described. Jumpering is most probably not the issue. These exact same circuits have been in use for nearly 3 decades and they work just fine.
"They work just fine" on something entirely different.
"PIN 13 is connected to RX0 and PIN 14 is connected to TX1 on the Arduino"
Pins 13 and 14 of the MAX232 are supposed to go to the RS232 device (the radio, if it's an RS232 compliant port - Is It?
The Arduino pins are not RS232 at all - they are TTL/5V.
Refer to the dwg in my previous post (Reply #3)
> > > The only MAXx232 pins that have any business going to any Arduino I/O pin are 9, 10, 11, 12