Practical Question and Answer series
For more questions and answers see the
Q&A Index.
4) How will I manage long-distance
communication?
As usual, I'll break this question down into several parts to
make it easier to deal with. So I'll look at methods of communication
based on radio, visual, auditory, and cable transmission, as well
as the physical movement of messages.
For various methods mentioned below a knowledge of Morse code is very handy.
(See this online applet which will translate text to Morse
code and even play it back to you as audio.)
Another useful skill is a working knowledge of cryptography so that you
can hide and encrypt messages that you do send. Even a simple
cipher, a method of rearranging
or substituting words or letters in a pre-arranged way that the
receiver understands, can make your communications less vulnerable
to evesdropping. Prearranged code words or signals can also help.
Radio communication:
Regular In the Wake contributor MM actually emailed me a great
answer to the communication question several months ago and I
haven't posted it until now. MM suggests using ham radios for
communication in a collapse context. I think that's a great idea.
"Ham radio" is a catchall term that refers to amateur radios with
a wide variety of types and transmitting powers. You can find
out more general information about ham radio at this introductory how-to and at this
introductory page
of the (US) National Association for Amateur Radio. Ham radio
does require electricity, but a smaller model (with a shorter
range) can use surprisingly little. (There are other types of
radio, but mostly have a very short range or are not currently
accessible to amateurs.)
In most countries in the world you will currently require a license
to operate a ham radio. You will probably have to write a test
to get that license.
In terms only of range ham radio is by far the best of all options
discussed here. Depending on weather conditions a ham can transmit
incredible distances, even to other continents, by bouncing the
radio signal off the moon or upper atmosphere. It can also transmit
a variety of different forms of information, including Morse code,
voice and audio, data, and even video if you have access to and
electricity for all of the required devices.
One of the downsides of ham radio is that because it can transmit
so far it can also be overheard by a great many people and is
not an inherently secure or private means of communication. MM
points out that there are electronic devices called "scramblers"
which can encrypt and decrypt communications to increase your
communication's security, assuming you have electricity to spare.
You can also use general cryptography techniques as suggested
above.
For more information about ham radio in general, check you can
visit DXZone.com and also
the National Association for Amateur
Radio. Many ham radio users also have a lot of interest in
hacking or modifying their own equipment, and you can find out
more information about modifications that you can make at mods.dk
and HamRad.com.
Useful books about ham radio include Now
You're Talking!, 5th Edition (which focuses on ham licensing
requirements for the US), The
ARRL Handbook for Radio Communications 2005, and Ham
Radio For Dummies.
Visual communication:
Smoke signals are the one of the oldest methods of communicating
over a distance visually. The method is pretty simple. A campfire
is built, and materials like handfuls of grass or green leaves
are added to produce more smoke when needed. A cover (such as
a damp blanket) is placed over the fire to stop the smoke, and
then the cover is removed for a few second and then replaced to
create puffs of smoke visible a great distance away. You'll need
to prearrange a code for what different numbers and lengths of
puffs mean. So even though anyone can see your signal, they don't
necessarily know what it means. The higher up your signal fire
is the greater the distance it will be effective for.
Which brings up the concept of line
of sight. Although ham radio operators can bounce signals
around, visual communications are limited in distance by the line
of sight, which simply means the direct and uninterrupted line
between the signaler and the observer. Since the Earth is curved
your altitude and the terrain determines how far you can signal
when you are limited to a line of sight. If you are on completely
flat terrain and you are signaling from a height of 2 meters (6.5
feet), and the observer's eyes are at the same height, you could
signal to a maximum distance of ten kilometers (6.2 miles). Beyond
that, the observer would be beyond the horizon and not able to
see the signal. That distance in theory and not in practice, since
foggy or misty weather conditions and obstructions like trees
or other factors could reduce the distance. If your signal were
on a hill or tower that was 30 meters (100 feet) high, and the
observer was at another hill or tower the same height, your maximum
visible distance would be 32 kilometers (20 miles).
[To calculate the distance for your self, you can use a simple
formula that calculates the distance of a position to the horizon.
Metric: Square root of (13 x height in metres) = Distance to horizon
in kilometers.
Imperial: Square root of (1.5 x height in feet) = Distance to
horizon in miles.
Find the distance to horizon for both the signal source and the
observer, and add them together to find the maximum line of sight
range.]
Another simple method of visual communication is mirror signaling.
Mirror signaling is actually very easy to do and learn, and simply
requires reflecting light from the sun (usually) towards the observer.
You can read about how to make and use a small
signal mirror. The larger a signal mirror is the easier it
will be to see at a distance. You can improvise a large signal
mirror by taking a regular space blanket and stretching it taut
over a frame. You don't necessarily have to move the mirror to
change the signal. Many signaling devices historically placed
a set of shutters between the mirror and the observer which would
open and shut rapidly. This can make the signaling easier to do,
and allows you to easily use systems like Morse code.
The downside is that signal mirrors are really only useful in
the day since they use the sun as their energy source. However,
you can use another light source and place shutters over it as
mentioned above. An array of LEDs with a focusing lens could be
visible at a very great distance and require relatively little
power. It could also be turned on and off rapidly without using
shutters.
For all of the visual signaling systems mention above, binoculars
or telescopes can significantly increase the observer's ability
to make out the signal. For more related information about visual
signaling, check out the Wikipedia article on semaphore communication.
Auditory communication:
Perhaps the simplest of all the categories, auditory communication
uses sound to send information.
Historically, bells and drums have been some of the most common
ways of using sound to communicate over a distance. Again, you'll
have to come up with your own signaling code. Drums and bells
can be effective at a considerable distance. Drums specially shaped
for communication, sometimes called talking
drums, can be effective at distances of up to 8 kilometers
(5 miles).
In some places whistling languages have been traditionally used,
which are effective at a range of 1 to 2 kilometers (3000 to 6000
feet), but can sometimes be used at up to 5 kilometers (3 miles).
For more information about whistling languages, see the Wikipedia article on
the subject.
Cable transmission:
You can build an electrical telegraph
very simply if you have a loop of cable which travels from the
transmitter to the receiver. All you require is a battery or electrical
current source, a switch on one end to open and close the electrical
circuit to actually send the message, and a light or buzzer on
the other end which will receive the signal. Morse code was originally
invented for this type of device.
With slightly more complicated equipment you could also improve
a phone or intercom system. One downside of this system is that
it could easily be tapped.
Another modern cable that you could make use of is fiber optic
cable. Fiber optics transmit light from one end to the other internally.
So you can use a flashing light at one end to transmit to an observer
at the other end of the cable. Fiber optics have become quite
common in the global telecommunications network, so you may be
able to find long lengths of cable to repurpose.
The disadvantage of all cable transmission systems is that the
cable has to be fairly long to be more useful than other methods
discussed; and the longer the cable is the more likely it could
be damaged or severed intentionally or unintentionally. If the
cable is buried for protection it could be even more difficult
to find a break.
Physical movement of messages:
It's pretty obvious that you can send paper messages by simply
passing them with trusted travelers from one place to another.
But there are some more creative methods. For example, homing pigeons have been
used to send messages for nearly a thousand years. Homing pigeons
are trained to return to a certain location. Once they have been
trained they can be carried away from that location, given a message
affixed to their leg, and then released to carry that message
back. However, as with any practice requiring the involvement
of any non-human animal various issues around ethics, good treatment
and consent emerge.
To be even more creative, if you need to quickly bridge a gap
such as a dangerous river or a valley, you might also consider
hurling messages attached to a weight like a baseball from a device
like a catapult. (see Trebuchet.com
and the How Stuff Works page
on catapults). As another option, a bottle
rocket similarly requires no electricity, just pumping to
build up pressure. Although most bottle rockets use two litre
pop bottles, you can use whatever you have available as long as
you select a bottle that won't burst and harm someone while being
pressurized. Custom-built competitive bottle rockets have reached
heights of up to 500 meters (1600 feet).
With such a variety of options to start from, I fully expect
that people will come up with all kinds of creative decentralized
methods of communicating and coordinating over long-distances.
The resulting system will probably be a patchwork over various
overlapping methods because no one method is appropriate for every
terrain, climate or group. Since every method (except for long
distance ham radio) has a limited range, important or interesting
messages will certainly be relayed from signaler to signaler over
much greater distances.
Update, February 1, 2006: After reading what I wrote
about homing pigeons above, Lierre
Keith writes:
I used to keep a small flock of homers. They're
great. The best resource is Racing
Pigeon Digest and the pigeon forum at www.poultryconnection.com.
One of the other good things about pigeons is that they are incredibly
intrepid and self-sufficient. Witness how they can survive even
in the middle of cities where other birds fear to tread. Lots
of poor city dwellers kept pigeons because it was a dependable
if small source of meat. They reproduce every six weeks, and remember
that until recently people understood that the organ meats were
the most nutrient-dense food. So every bit of the birds would
be eaten and then the bones used for broth.
Update, February 2, 2006: Justin writes:
Just so you know, recently a technique has
been developed for two way communication via carrier pigeons.
They are trained to receive their food in one location and sleep
in another. This technique is now employed in Puerto Rico and
Guatemala, and other places.
See http://www.nap.edu/books/030904295X/html/142.html
Justin's link is from a larger free book called Microlivestock:
Little-Known Small Animals with a Promising Economic Future
which has other interesting information in it.
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