Ryan - KJ7GIE
I exhausted all cable troubleshooting and I was really getting down on myself. But, I had also convinced myself that, yes indeed, the cable must be good. If it wasn't the cable it must be the GPS sentences. The silly radio must simply be throwing away what I was sending it. Why would it do that? Did it not not like the sentences... did it not like... hmmm... wait... is this thing _that_ finicky that any misalignment across a row would cause it to throw away the sentence? Yes, it's that finicky.
The PC looks for GPS sentences which start at "$GP" but that isn't good enough for the spec; or the radio. The NMEA spec is that the sentence must start at the beginning of the line and end with a CR/LF (carriage return / linefeed). And, after just literally staring at the output for almost an hour, I started to realize that this GPS / serial set-up wasn't entirely accurate with starting at the beginning of the line which meant the CR/LF was probably also not landing at the end of the line. PC happy. Radio no.
I'm now taking the GPS sentences off the serial, reformatting them, and pushing them out to the radio. Radio go happy now! Funny thing is that this is assisted by my old unix friend unix2dos:
cat /dev/serial0 | unix2dos -f > /dev/serial0
Now to clean-up the shack of all my little experiments and button this thin up.