Using the latest technology, what is the farthest distance two people could communicate by voice or text without relying on any infrastructure beyond portable devices that each of the two could hold?
If I traveled back in time with a pair of smart phones, they would be useless on their own without the whole network that supports their use.
If I brought a pair of good walkie talkies with fresh batteries to the year 1630, though, it seems I might be able to communicate several miles over flat terrain. But most likely not from Boston to Plymouth, MA, I would think. We could maybe push it up to 20 or 25 miles from the tops of hills on a clear day.
Is there anything else beyond a battery operated two-way radio that would allow voice communication without additional power, cables, towers, satellites, etc.?
Ham radio can reach around the world, using the right frequencies and time of day. All they would need is power for the transmitters (and receivers). That could be provided from batteries, although it wouldn’t be pocket-sized.
It’s ironic that your best choice for long distance communication with no infrastructure is a roughly 75 year old technology.
Handheld ham radios probably don’t have the power or antenna gain to do much DX, but there are mobile units meant for installation in a vehicle that would have the advantage of a larger battery and larger antenna. Decently portable if you don’t mind carrying a 40 pound car battery or two, but eventually, you’ll need to figure a way to recharge it. Better pack some solar trickle chargers in your time machine.
Probably further than that. Ham operators listened in on the communications from the Apollo astronauts, though I’m not certain that the equipment on both ends could be “hand-held”.
And since you’re probably going to ask about line-of-sight issues with communicating around the globe, that works by bouncing the signal off of layers of the atmosphere. One reason it depends on being the right time of day is that those layers change with sunlight and temperature.
Lugging around car batteries would be a problem for the time traveler, I think. I guess the next question would have to be what’s the greatest distance we could expect with something people might be carrying if they were not specifically intending to time travel–two kids get sucked back to the stone age with their Nintendo DSes or a pair of hikers with walkie talkies stumble into a time machine.
It can’t be Frank and Sue were hauling a couple of ham radio sets and bulky battery packs when suddenly they and their hand truck fell down the rabbit hole.
And not to hijack my own thread, it might be interest to note how many everyday things have not been much improved by technology in the last 75 to 100 years. . .
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I guess the next question would have to be what’s the greatest distance we could expect with something people might be carrying if they were not specifically intending to time travel–two kids get sucked back to the stone age with their Nintendo DSes or a pair of hikers with walkie talkies stumble into a time machine.
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For the kids, about as far as they can yell, unless a Nintendo DS can work as a radio, and for the hikers, assuming they have generic FRS radios like the ones sold at Walmart, they might be able to get six miles apart. Possibly a bit more, since they won’t have to fight against all of the other radio signals in the air today. If they have GMRS radios, they may be able to attain 20 miles with clear line of sight. In practical use today, range is much less and perhaps one fourth of the advertised “up to” ability.
Well, not to double-hijack, but consider the last really major improvement of ships. Other than getting enormously larger (crude carriers in one way, cruise ships in another) they haven’t fundamentally changed since about the 1880s. (Nuclear power is interesting, but doesn’t provide anything other power systems had except very long refueling cycles.)
What about semaphores, morse code with a mirror, and other light dependent systems. A small laser can show pretty far in good conditions.
Sound, drums, even explosives, though a bit cumbersome for a long discussion.
Simple signals like smoke, balloons, birds
These were probably not the OP’s objective, but I was surprised to remark that communication seems to have started in the 20th century (at least in this thread). European monarchs were notified near immediately using hilltop to hilltop light codes, sometimes over hundreds of kilometers.
You’re correct, cplif, about historical long distance communication, but I was thinking more of something involving voice or text that could be accomplished on the fly: alerting Lexington and Concord know the Redcoats were moving without sending guys on horses riding through the countryside and such. Calling to an associate across town while you’re running through the streets. Sure there was the light in the tower of the Old North Church, but somebody had to be positioned and waiting to look for it. Not as handy as having the phone vibrate in your pocket while you’re in a tavern twenty miles away.
The after effects of such communication have lasted to this day. Many Jewish holidays are celebrated for two days outside of Israel.
From the Lubavitcher chassidic sect site, Chabad (say that fast )
Originally, the starting date of every new month was broadcast from Jerusalem to distant Jewish outposts via huge bonfires which would be lit on designated mountaintops. Lookouts stationed on other mountaintops would see that a fire had been lit and would light their own fire. This chain of communication led all the way to Babylon, and even very distant communities knew when the new month began. If there was a festival that month, they now knew when to celebrate it.
But a problem arose. The Sadducees, a sect of Jews who denied rabbinic authority and were constantly at odds with the Sanhedrin, started lighting fires on the wrong days in order to manipulate the calendar.1
To prevent this confusion, the fire-on-mountaintop method of communication was discontinued, and instead messengers were dispatched to Babylon and all other far-flung Jewish settlements.
Since news travels a lot slower that way, distant communities would not know when Rosh Chodesh (the “Head of the Month”) had been declared in time to celebrate the festival on the proper day.
It was therefore decreed that outside of the Land of Israel people would celebrate two days for each festival – the day it would be if the previous month had been a 29 day month, and the day it would be if the previous month had been a 30 day month.
I am a ham and I primarily operate QRP or low power.
I currently use a Yaesu FT-817ND which has a maximum power of 5 Watts. That 5W is decreased by a lossy autotuner, coax and non-resonant/gain/rotatable wire antenna strung up in my attic ceiling. While I can’t reliably do it every time, I’ve had successful two-way voice contacts to distances over 5000 miles.These would be to South America and Europe/Russia. I can usually reach either coast on one band or another. Last weekend, I worked Cuba using 1 Watt and partially worked Venezuela with one watt but he kept getting one letter of my callsign wrong and I had to increase power.
I run exclusively on a 6 Amp-hour lead acid battery which is probably somewhere between 5-8 lbs. My antenna is made of ~35 feet of wire from salvaged Cat5 ethernet cable. The tuner and cabling are probably under 5 pounds.
I don’t think my rig could be called handheld but it is certainly easily packed and hand carried. If I had a few trees or structures to string up my antenna, I’m certain I could talk out for hundreds or thousands of miles unless conditions were really poor.
I also have a military manpack radio that I use a few times a year. Contacts of hundreds of miles are not uncommon. 100% portable and self contained. Waterproof and hardened, too.
If you have sufficient chemistry knowledge or enough sheer luck, you should be able to manufacture batteries in any time period. They might be bulky or not have much energy in them, but you should be able to get enough voltage and current to run a radio. Remember the potato clock?
If the question is “what is the most powerful portable communication system TODAY?” there may be coherent answers. If one states the question as the OP with the grid down (as in time-shift or war etc.) it becomes problematic.
Rebuilding even a simple grid ( on both ends) is a big job, under the given circumstances, other priorities are present, word communication to distant people may not be one of them.
Existing infrastructures were built mainly for commercial reasons, (communication, energy, transportation), your immediate needs may be vastly different. It may be faster to simply walk to your correspondent, and “where did you put my wallet?” type of communication is probably unnecessary anyway.
Actually, the same question can be posed for even simple written communication. ie, if I can easily carry a letter, do I have the know how to build from scratch a writing tool, and writing strata, or some other means of conveying enough information to make the whole thing worthwhile. Even making some sort of pen (quill), then ink, and some sort of paper or light substrate is a time consuming process.
I doubt that finding yourself suddenly off the grid, you would set your priorities up this way. Either your time machine is bringing you back pretty soon, or much thought about sustainable living is the priority, fast long range communication may or may not be part of this.
good luck anyway
The way the question came about was I was reading a YA fantasy/adventure novel written by an old high school classmate, THE CRIMSON SHARD. In it, two teens, without preparation, go back to 18th Century London. One is carrying her cell phone, which is useless and doesn’t figure into the plot at all, really. (They convince somebody from the past that they are from the 21st Century by showing them a glossy, printed brochure with full color photos of modern London.)
Anyway, a one point, when the children were separated, I thought, “Too bad she can’t use her phone to call him.” That made me wonder what they could have carried back to the 18th Century that would have worked in that situation.
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