Cool topic! I'm a big proponent of a new, independent network, similar to how the Internet itself was first created way back. Independent and more resilient than the current infrastructure.
Keep in mind: a network
just for Bitcoin poses a few issues. For one, everyone will know if you use this network, that you use it for Bitcoin. Furthermore, it can be more easily banned or prohibited. It would be better if this new network was more generic and e.g. we also had messengers operating through it.
If power or the internet goes down, it's safe to assume that Bitcoin becomes practically worthless/useless in an instant for anyone who's living the aftermaths. We're talking about situations like the current one Lebanon is facing. Had this happened in a much larger nation like the US, I think Bitcoin would've confronted a huge sell-off and loss of interest/trust.
Online banking or traditional banks in general are as reliant on electricity and internet as well, though. I am pretty confident even a brick-and-mortar bank doesn't work without internet connectivity. Did people lose all trust in their bank when they couldn't go there due to blackout? I haven't encountered this so far.
I think ham radios can be used to send e-mails.
That's correct; you can even run a complete TCP/IP stack over ham radio. However, it requires a license (at least in all the countries I know of), very specialized hardware and
no encryption is allowed. That's the biggest culprit in my opinion. No TLS! No bueno, in my honest opinion.
There were some kind of radios that you could transmit over a range of up to .. 200 miles (or kms) as well? Is there absolutely no way this can be done?
Yes, it depends on the frequency and thus on antenna size though. For example very low frequency signals travel insanely far, but have a terrible data rate and require antennas literally the height of someone's home.
We have so much technology to use and Bitcoin is imo still just at the beginning. Building a rechargeable device that allows for fully offline Bitcoin txs to happen would make it about invincible even in disastrous events. Is this a bad/impossible-to-realise idea? What do you think?
It's certainly possible to build and I'm very interested in the topic. One feasible way is to create a 2.4GHz mesh network using directional antennas. It should be possible by repurposing 2.4GHz routers with a custom firmware and attaching directional / parabolic antennas to them, of course positioned outside. The ranges as far as I know are around 10-20km, so you'd need a few people in every city running one such thing to get a good coverage. That's why I say mesh network.
Here's an unrelated video that shows what off-the-shelf hardware can do in the 2.4GHz band:
https://youtu.be/15JmpVAuzZY