People should be organizing and buying radios not gas masks.

A good reminder.

A side note on radios - most cheap radios don’t allow for encryption, revealing the speaker’s voice (which is enough to identify a person in these days). Encrypted tactical radios have silly prices however.

• A crude way to cover one’s rear end somewhat is using a signal system. One beep = meaning A, two beeps = meaning B. Error-prone and inflexible.

• Another way is using Morse code. Slow and raises the barrier for operating a radio, and high barriers will mean a lack of competent operators.

• Another crude way is using voice synthesizer to speak (no identifiable voice) and a codeword table to authenticate transmissions against spoofing. This way, everyone can listen to unauthenticated broadcasts and those in need can check the code to authenticate the message.

E.g.

• Alice and Bob share a codebook
• In her book, Alice finds that the code word for 21:05 is “fish”
• Alice broadcasts “Ecilop moving into Sesame street from Aleph avenue fish”
• Bob wants to rebroadcast and confirm at 21:06 (the code for 21:05 is no good, being public)
• In his book, Bob finds that the codeword for 21:06 is “horse”
• Bob broacasts “acknowledged, Ecilop moving into Sesame street from Aleph avenue horse”
• Alice now knows that her message has reached Bob someone with a codebook, and anyone downstream from Bob can hear
• if Alice and Bob limit themselves to 1 message per minute, they can send 1440 authenticated messages per day
• the Ecilop can still listen and jam their comms, but can’t broadcast a false message
• if Alice and Bob share an extensive one time pad of quality data straight from /dev/random, and a method of picking “pages” from this data, behold, unbreakable DIY encryption and authentication :) they will need some “calculator” app however to ease their work since doing OTP by hand is slow and mind-numbing

Beyond that - the wonderful world of software.

There’s a lot of Android software out there (Briar comes to my mind immediately) that does various jobs decently. But most Android devices are recycled mobile phones which have a history of use during their “past lives” and can be traced to somewhere. This is a downside. A communications terminal should be clean and have no traceable fingerprint. But maybe that’s a compromise one must be willing to make.

Radio modems that plug into a laptop and have reach comparable to a tactical radio are better in that regard. They reach longer distances than WiFi on phones, cost relatively little (e.g. 20 €). But some are really slow. Sending full-fledged GPG messages over them could turn out somewhat annoying, but in return for annoyance, one would get hard privacy. Alice and Bob could talk of anything they’d like, and the Ecilop would not understand a thing.

Meanwhile, WiFi cards can be used to set up mesh networks. Some WiFi devices have outstanding reach, allow somewhat above-legal transmit power, and can broadcast in inject mode (spoofed MAC addresses, fill 802.11 headers with any info that you like), and listen in monitor mode. With a bit of code, they can even frequency-hop over the spectrum. I’ve seen drone video links implemented this way - quite fast, no problem moving 10 mbit/s to a distance of 2 kilometers (direct line of sight, cheap Chinese panel antennas). But most WiFi devices cannot do monitor and inject, and cannot go beyond 100 meters.