Hi there jackson_r!
Avoding 'the knock' is always a thing thinking about.
"daddy, what are you doing" in the background while I was trying to live broadcast wouldn't work so well.
Aww! I love kids. That'd be fun!
Audio-Output 2 MIC: Naa, that's no rocket science. Maybe ask for help with the soldering in your circle of friends or relatives? Help ist just around the corner most times. Without reading the manual for the baby you have your eyes on: usually it takes two modifications:
- Bridge teh PTT switch so it's broacasting permamently.
- Adapt the voltage level of the headphone out to the MIC input. That's usually 2V to 2mV. That can be done by a simple resistor based voltage divider. In case you keep on your actaual plan and need some help with the valkues: poke me.
About the Solar-Power thingie: If you're not happen to live somewhere with a LOT of sunshine all day long (like in a country/state around the equator) that can be tricky. I hate to ruin the fun but it won't work in areas with something called "winter" and "snow" around.
Basic calculation: We assume you whole rig (with 5W PO) consumes about 1,5A. For one day that's 25h*1,5A = 36Ah. That the entire charge of a full standard (small) car battery.
A standard value for solar charging estimates (during summer) 5 sunhours (with full power) per day. 36Ah / 5h = 7,2A. That's a 180W (+) PV Panel. The dimensions for such are approx 1x1.7m. About 150 bucks (ebay). And it won't be easy to hide.
And this goes for perfect conditions. Rainy day? Forget it. You're out of power. We still assume you have nothing called "winter" in your area I'd say you've to go for 300+W PV power to provide a stable charge into a (at least 88Ah) battery.
(those are all quick'n'dirty calculations. Doing a proper evaulations that ensure a reiable power supply will be way more complex. I forsee from that for now.)
Also, a car battery will wear down within one year (or less). They're not made for full swing (dis-)charge cycles. You can, of course, go for a special battery made for solar operation. But, eh, expensive. 75Ah is about 250 Bucks.
Other sidenotes: keep an eye on the specs of the Radio. Is it made for long term key-down operation? Also, when putting it outside: spend some thought on the ambient temperature. In case sun hits the box the ambient temperature can easily exceed 60+°C. The device temperature adds to it. 90°C isn't unlikely.
Greetings,
~Zazzle