53

How I've practiced is I hold my left hand palm out, and I create a "V" between my ring and middle fingers with the plane or person between my fingers. I then hold the mirror by my face and shine the mirror between my fingers. You should see the light on your hand to confirm you are shining in the right direction.


26

A modern (Korean War era and later, at least) signal mirror has a hole in the center, and the hole is surrounded by a grid of retroreflectors. You aim the mirror spot at something close by, then look through the hole. The grid makes a very bright spot where the mirror's reflection is going. You then simply tilt and rotate the mirror to put that spot on your ...


23

In both the U.S. and Canada, amateur radio operators serve an important role in providing emergency radio communications during war, disaster, terrorist attack, or whatever other emergency. So amateur radio operators take an extremely dim view of unlicensed operators using frequencies allocated to amateur (or sometimes commercial) radio. Many will even hunt ...


20

There is a definitely a risk of starting a fire with a flare gun, for this reason they are discouraged by the National Park Service (at least in Grand Canyon-Parashant National Monument). Not Useful: Cell phones do not have service in the monument Flares are not always visible to pilots flying overhead during hours of sunlight or in heavy overcast skies. ...


19

This answer applies only to signal mirrors which are two-sided and have an aiming hole in the middle, which should be the case with any good signal mirror. My answer will partially duplicate a prior, but will add some rough pictures and also give a description of the geometry behind how it works. The process Stand facing roughly half-way between the sun ...


18

Charles Brumbaugh's answer is correct if a helicopter rescue is underway and you need to warn an approaching helicopter that it should abort the approach due to some problem you have spotted. (From Charles's second linked document: "Should the helicopter move in close before you are ready, or you see a problem, face the helicopter, cross and uncross your ...


15

Your signal mirror is likely polished on both sides, with a hole in the middle to help you aim it. Although the principle is simple, it's fiddly and takes a little practice. With the mirror in roughly the right position, arrange for its shadow to fall somewhere suitable (e.g. flat rock) so you can see the central spot of light. Now, line up the hole with ...


11

From Scouting For Girls, Official Handbook of the Girl Scouts Whistle Signals One blast, "Attention"; "Assemble" (if scattered). Two short blasts, "All right." Four short blasts, calls "Patrol Leaders come here." Alternate long and short blasts, "Mess Call." From Scouting for Boys: A Handbook for ...


11

Iridium uses radio frequencies around 1.6 GHz or 18.75cm wavelength. Atmospheric absorption at these frequencies is very low: Clouds contain water droplets, though. So, let's have a look at rain attenuation: ...no problem either at 1.6GHz. So your answer is: overcast weather should be absolutely fine. The designers wouldn't have picked a frequency that ...


9

International standard and very easy to remember is the Y or N signal. If you want to communicate more than that, your signals should be easy and self-explaining. If you are e.g. climbing and it's not that obvious who needs help you could also inform the rescue team in the helicopter by pointing to the casualty after signaling Y.


8

There used to be an article on the homepage of the Austrian mountain rescue service concerning behaviour during helicopter rescues, originally published in Berg und Steigen 3/02 (a professional periodical on mountaineering safety, but in German). This article was written by actual rescue helicopter crew and contains a section about helping in the search ...


6

The sun isn't a laser, so you don't actually have to be very accurate. The further away your target is, the less accurate you have to be as the reflection will spread.


6

I would say that the alternatives in the the answers to the linked question would be a better idea, but if you had to use a flare then there are a couple of things that could lessen but not eliminate the risk. Shoot the flare in such a way that when it comes down, it ends up in a body of water such as a lake. If that is not possible shoot it in such a way ...


6

Flares ignite at 191 °C (376 °F) and burn as hot as 1,600 °C (2,900 °F). This makes them incredibly dangerous since they are well above the ignition temperature of most flammables found in a forest or wildland. My experience firing a parachute flare such as a Pains-Wessex at sea level, the air is thicker and they tend to hit the ground unlit. Further in ...


6

Excluding the legality question, as to be honest, that's likely to depend on who detects you, and how much it interferes with licensed traffic, the safety angle has a couple of aspects: It doesn't look like you will clash with emergency services, however there is a risk that you will clash with local amateur radio operators who may be handling emergency ...


5

I am an amateur radio operator (Extra Class) active in Skywarn. Yes, PMR radios transmit in the amateur radio spectrum in Canada and the U.S. Yes, it is not legal. In the wilderness, far away from civilization, and with handheld radios that emit a few hundred milliwatts, you will absolutely, positively not interfere with anyone. If by the smallest of ...


5

What you are looking for is a walkie-talkie / two-way radio / private mobile radio with voice control. Normally, to communicate with a walkie-talkie, you need to press a transmit button. Some models, however, have voice-control: they will automatically start transmitting based on voice input. My friend and I used the Midland G7 XTR, that includes this ...


5

I'm sure this isn't what you were shooting for but using radios, satellite phones, cell phones, etc. would all count because they transmit the "noise" of your voice to your target where it is reproduced as noise. So in a way it is kind of like teleporting your words/noise exactly where you want it to go or speaking in a targeted echo chamber. :) The ...


5

Personal radio devices in Europe use a different frequency (446 Mhz). According to a quick google search the frequency range of GMRS/FRS (462-467 Mhz) is used by fire brigades in UK, police in Russia and licensed radio amateurs in Germany... blocking frequencies of police or fire brigades will certainly cause you trouble here.


5

Beyond the previously mentioned Scouting communication guidelines, Morse Code is definitely an option. However, Morse code isn't as widely known anymore and could potentially be misinterpreted as a call for help. Any distance coverable by a whistle in backcountry could also be covered by a two-way radio. Cheap'ish hand-held radios are a staple for the ...


5

Percussion Drums have been used historically to communicate over long distances in forested areas, so you could send messages simply by knocking on wood. Pick up a couple of hard sticks, and knock them against each other or something else that has some good acoustics. You could communicate with morse code this way, and the average traveler would just assume ...


4

I looked at some different plans and it looks like you could buy a prepaid plan and not activate it for up to 2 years. See the pricing here. However that seems like the really expensive option. Since you only want something for use in emergencys and want to be able to communicate with rescuers which rules out PLBs, I would suggest a inReach instead. That ...


4

I spent a summer with two brothers from the Dominican Republic and they would call out to each other with a loud howl-like "FOOOOOOOOOOOO" sound that carried very well through fields, forests, and over a lake. Later in life I spent some time with a friend of a friend who was essentially squatting and setting up a semi-permanent settlement in the jungle. Him ...


4

If anyone has hiked in the woods knows that noise may not travel very far, especially in dense forested areas. So the use of any whistle would imply that group members should be relatively close together. It is of little importance what "standards" a particular group uses for their whistle signaling for communications, as long as everybody uses the system ...


4

I have an inReach and have used it in all sorts of conditions and terrain. Overcast weather is not a problem but a reflective tarp or deep canyons can be. If a message fails to get through the device will flash red and that means you need a better position. Normally it’s not a problem.


4

Incoming messages count against the limit of text messages. Yes, any message sent back to your inReach device, including replies to preset messages, count against your monthly message allotment. Source But it will not cost the person sending you a message.


3

The nice thing about standards is that you have so many to choose from. - Andrew S. Tanenbaum While there are standards you and your companions need to know and agree upon what that standard is prior to having an issue. That said it's fairly common to understand ongoing whistle blasts to mean something isn't right or HEEEEEEELLLLLLLPPPPPP. A sampling of ...


3

Although the question specified using no equipment beyond a standard mobile phone, I think it's worth pointing out that VHF and UHF radio signals can typically be heard over greater distances than a phone signal, and shortwave signals even further. If you are planning to travel into remote areas with little or no phone service and with an elevated risk of ...


3

In the EU (including the UK), SMS to the general emergency number (112) appears to be widely supported technically, but several countries I checked appear to require pre-registration. It's not clear whether that means SMS from unregistered numbers would be rejected. In the UK, the British Transport Police have an SMS shortcode: 61016. This is intended for ...


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