Signalling devices

Satellite dish.
If you understand how sound travels you understand the value of the giant ear.

 

Swiss Alpine Horn LOL
couldn't resist reposting.
military used cricket clickers back in the day.
U.S. Military D-Day Cricket Clicker, Reproduction

 

Any thing wrong with. FRS radios much longer range than several methods that have been mentioned.

 

A package or so of any red form of Kool-Aid or unsweetened Jello goes a long way on snow and ice. Weighs virtually nothing.

 

Dad would say, if you need to get a message out, don't telegraph or telephone, You tell a woman.

 

(Well. Better late than never...I got caught in one of my old traps and had to gnaw my leg off. Again.)

Given that the internet is still up and you want fast & pretty secure communications, just...

Invite somebody to a nice game of WoW (or any similar role-playing game) group up and then chat with them head-to head.

You can get the whole tribe in together for updates, assignments, or whatever.

You can also get an extra layer of security by talking in a written "verbal" code.

Just make sure everyone has the right cheat-sheet.

"Got blasted last night and puked my toenails up." could mean
"... .Meet..10PM...tomorrow...bring.....all weapons"
or
"......Make...next regular.....delivery...cold...beer."

Or, if security is vital you can use a book code with page, paragraph, and word numbers from some worthy tome like Atlas Shrugged or War & Peace. It'll take the opposition two and a half forevers to figure out that you either just
a) set up another pizza party,
or
b) decided to bomb the Brooklyn Bridge.

Again.

A riddle for all the crackers of code out there: 1,1,1/1,1,2 yields the message "Call me." From what book is the code taken?

One last quick comment on communications:

A family (or team) that takes the time to learn a mentalist code can say anything they want in front of anybody, and the listeners won't have a clue. They won't even sound suspicious.

It takes effort, but it can pay off big, even if you and your sweetie are just dickering with a used-car salesman.

 

Moby Dick?

 

Bingo!

 

Good points, all.

There is no code that can't be broken, if only because the message contains information.

Cracking the Zodiac Killer's code took fifty years.

I guess the best one can hope for is to stall the enemy until the content of the message is totally obsolete.

I guess one could make the opposition's job harder by starting somewhere near the middle of the book and counting backwards...

 

A bouquet of flowers set at a particular arrangement sent secret messages in the olden days.

 

There is no code that can't be broken, if only because the message contains information.


wrong. One time Pad codes can not be broken with this caveat. 1. You never reuse a one time pad. Thus the name 1 Time pad meaning you only use it once. If you use it more than once you can start to see patterns and thus break the code. 2. Dont leave the cipher out for the bad guy to collect. Once the one time pad is used the cipher pad must be destroyed and never used again.
No one time pad that has ever been used that was done properly has ever been broken. There are still one time pad codes that still haven't been broken to this day.

 

spark gap transmitter
.

used commercially back in the day (sounds like this)