Before we get into the specific equipment I thought it is worth mentioning a little about radio waves. All wireless communication uses radio waves to send and receive messages. Radio waves are similar to the waves on a beach. Waves have two main properties, firstly the frequency (how often the waves hit the shore) and secondly the amplitude (how tall or powerful the waves are). The light we see is also a type of radio wave, the colour changes with frequency. Red is a lower frequency and blue is higher. The higher the amplitude the brighter the light and the further away it can be seen.
To send messages the transmitter creates little imperfections into each wave and the receiver then decodes those imperfections to give you a message. The higher the frequency the more information you can encode (because there are more waves per second). This means clearer voice or more data. The larger the amplitude the stronger will be the signal when it is received, which means less information lost along the way. So you clearly want the highest frequency, highest power transmitter, right? Not really. High power means rapid battery drain (which adds to your pack weight). Also, the higher the frequency the shorter the distance the signal will travel before getting messed up.
Line-of-sight refers to a signal limit to travel in a straight line similar to your torchlight.
If there is a big object like a hill, then it will absorb the entire radio signal. Many radio systems use repeater stations to retransmit signals giving you wider coverage. Mobile phone and two radio networks place their repeaters on top of hills and satellite systems place their repeaters in space. With space-based repeaters, there is less often anything significant between you and the repeater, so they offer the widest coverage, higher frequencies and lower power use.
At lower frequencies (between 1 & 30MHz) signals can bounce off the atmosphere similar to light off a mirror. The AM CB uses this frequency range, but since the atmosphere is not as smooth or as stable as a mirror you can’t really predict where your signal will bounce too.
At about 2MHz the radio waves “bend” and tend to travel with the ground, allowing the signal to travel very long distances, but the equipment and power use are very large and the quality of the signal very low. These lower frequencies are generally used for Morse code rather than voice.

Okay, let's run through a bunch of ways of sending and receiving messages. I know there are other options. I have not included avalanche beacons, carrier pigeons nor messages in a bottle. Here are the more common, well know or more useful examples. These are broken into three main areas, very short range (low tech), ground-based radio systems and satellite systems.

Short-range communication can be easily ignored but they have their place. These systems are great for staying in touch with people in your group or others nearby. They work well with longer range communications, to help rescuers in the last few hundred metres.

Voice
If you are in a group and you’re struggling. Speak up before things go bad. If you are solo and struggling then speak to people you pass. Your voice can travel a few hundred metres. If you are waiting for emergency services then make sure you call out if you can hear them. If you are lost and waiting for help, move away from running water and into an area where you will be able to hear and be seen more easily. You can only shout for a fairly short time, so save your voice for when it is most effective.

Bright material
$10 or just use existing clothing.
If you are waiting for emergency services layout high contrast material that can be seen from a helicopter from a long distance. Make a large “V” for “require assistance” or a large “X” for “require medical assistance”. Just do what you can to get attention. Using a mirror to reflect sunlight towards a searching helicopter can help in difficult search terrain. If a chopper is close enough to be able to see you raise both hands in a “Y” shape, wave to get their attention and to let them know you need help.

Whistle
$10
A whistle is a helpful medium range communication device. If you become separated from your group then blowing
a whistle early enough will allow you to regroup with little fuss. It is much easier to blow a whistle then shout. A pealess is a loud and two-tone whistle. It is great that it’s accessible whilst wearing your pack. The two tones make it easier for people to pick the direction the whistle is coming from. A well-accepted international system is that three things (light flashes, horn blasts, gunshots, fires, whistle blows) communicate you need help. Blow your whistle for three seconds, three times in a row once a minute. Two whistle blows is a response meaning ‘come here’ and a single blow says ‘where are you’. Some groups also use a whistle to communicate in noisy environments like when abseiling in a waterfall.

Sending a runner
In a group, it may be possible to split so some people stay with an injured person and others take a message back to 'civilisation;. Splitting the group limits the resources available and can be a very slow way to get a message out. If you are sending a person to walk out a message, chat with them about the importance of the message and that they should take care, not rush. If they are injured and not able to continue then you end up in a very sticky situation (that you may not even be aware of). Handwrite a message for them to carry. Include a detailed description of your location, nearby helpful features, details of the injury (illness) as well as the person injured. Also details with your ability to cope with the situation (food, water, shelter, medical supplies, skills etc.).

Ground based radio systems are fairly common and easy to use. They have limited coverage but do cover many popular walking areas.

Mobile Phone
$30-$800 (+ connection)
Smartphones give you a bunch of other tools, not just a phone. Many contain GPS that with the right app and data can give you invaluable navigation help, even when out of mobile phone range. When in range you can check formal weather forecast, fire and flood information and update friends and family on your progress. Phones are not droproof or waterproof. Rugged cases for phones are a great way to protect you phone in the bush. Also consider carrying a spare battery or a portable charger for your phone. Keep your phone off or in airplane mode to save your battery and peacefulness.

Mobile phone coverage varies. Networks are mostly designed to cover areas where there are lots of people, generally places we avoid to walk. The coverage in many remote areas is still surprising, especially on top of hills.
Telstra has a group of phones they label as “Blue Tick”. These provide better coverage in remote areas. And Telstra almost always provides the best coverage in remote area. If you don’t have a Telstra account you can get a pre-paid sim card pretty cheap for your trips.

In an emergency
You can dial 000 from a mobile phone in Australia even if the handset is locked or there is no SIM card (assuming the phone is less than ten years old) and it is switched on. If your normal network provider is out of range your phone will automatically look for another network that is in range, i.e. if you are on Optus and out of range it will try Telstra and Vodafone. The person who first answers will ask if you want to speak to the Police, Ambulance or Fire. If it’s a medical emergency request for Ambulance, if you are lost ask for Police. Be ready to tell them which state you are in (Tas, Vic, NSW etc.) and your nearest town or national park you are in. When you are in a remote area you will need to explain to the Ambulance, Police or Fire operator that you are not near a road and provide your latitude/longitude and description of where you are. They have a series of questions to ask, be patient it can take up to 10 minutes. They will also provide you with some advice over the phone. If they have not asked you something you think is important please let them know at the end of the call or where it is appropriate. If you are short on battery let them know early in the call and get critical information across first.
Coverage can be difficult to predict and varies depending on the device, weather, soil conditions, vegetation and many other factors. Check out Telstra’s predicted coverage to get a sense of what service coverage is likely where you plan to walk. http://www.telstra.com.au/mobile-phones/coverage-networks/our-coverage/

Two way Radio
Some bushwalkers like to use high-end walkie-talkies as a way of staying in touch. Although the handset may cost a few hundred dollars there are generally no ongoing or usage costs. These tend to be popular with search, rescue and commercial operators.

UHF CB
$40-$200
Relatively cheap two-way radio’s great for short distance communications between nearby groups or longer distances where repeaters are available. Used by some groups to give updates in areas out of mobile phone coverage. Very limited by line of sight, but a fairly extensive repeater network significantly boosts the range in many areas.
Channel 5 is the emergency channel both in repeater or direct (duplex or simplex) modes. These are not always monitored. If there’s no response try calling on channels with accessible repeaters, otherwise monitor other channels for people chatting and interrupt the conversation. Larger antennas can provide much greater range.

Amature
$40-$500 ($73 annual licence fee)
Ham radio operators hold a special licence giving them access to a very wide range of radio frequencies. There are many repeaters as well as some very cool data (and GPS tracking) networks. A Ham radio can also access to a small number
of satellite services for both voice and data. Ham radios are only for private communications and can’t be used for commercial purposes.
To get a licence you need to complete a 50 question multiple choice exam. There are some dedicated emergency frequencies set up, but these are not reliably monitored. Great for chatting between groups and for playing with GPS (APRS) tracking data. http://www.wia.org.au
There are also a bunch of commercial and government Trunked Radio VHF networks but these are not practical for general bushwalkers (but may be used by search and rescue organisations). The RFDS also have a great HF network but the equipment is heavy
and large and therefore not practical for bushwalkers.

Getting the most out of weak reception

If your reception with a mobile phone or two-way radio is weak and you can’t make contact here are a few tips to try:
- Extend the antenna (if possible) - keep the antenna as clear from any object as possible.
- Walk to the top of a hill
- Use headphones or hands free mode and hold the phone above your head
- For mobile phones - sometimes you can send SMS but not make a call, SMS a friend who can help (000 does not receive SMS)
- Use a high gain antenna (blue tick mobile phone).

AM/FM radio
$60
A simple battery operated radio will often allow you to listen to radio broadcasts in remote areas. You can also get portable radios that pick up long wave (LW & SW) worldwide broadcasts. ABC has pretty good coverage Australia wide on AM. This lets you keep up to date with weather forecasts, Fire Danger ratings and fire or flood emergencies.

Satellite based communications are getting cheaper every year and becoming much more common in remote areas. Satellite systems provide the widest and most predictable communication systems.

Transmit only satellite messenger
$200 (+ $140-$210 a year)
SPOT is the most popular satellite communication system I see in the bush. It allows you to send messages
(like “SOS”, “I am Okay” and “A little help needed please friend”), including your GPS coordinates to predefined friends. The device can also be set to ‘tracking mode’ to send your location every 10 minutes (or every 2.5 minutes – 60 minutes with different packages) to a map that your friends can follow. Using your smartphone you can type a more specific message, even when out of mobile phone coverage. SPOT is transmit only, so you get no confirmation that your message was actually sent. SPOT transmits each message three times to increase the chance it getting through. My experience with my SPOT is that most messages have gone through. If you trigger the “SOS” feature it will send the emergency message every 5 minutes until it is switched off or the battery fails. The “SOS” message bypasses your friends and is sent via GEOS International Emergency Response Coordination Center to the appropriate emergency service in Australia. “SOS” is intended for emergencies only. Although it sounds similar to a PLB it uses a completely different network and does not have a homing signal to help SAR find your exact location. On some models of SPOT the SOS button is difficult to press.

Two way messengers
$360-$900 (+$12 or more a month connection - yearly contracts may apply) These are very cool, they’re getting cheaper and becoming more common. Think of them as a Satellite phone that only has SMS (no voice). You can get confirmation your message was sent and receive text messages from other people. Most allow you to also send messages to other units. Many now allow you to connect your smartphone to make typing a message much easier. The battery life on these devices are amazing and you can generally leave them running (not connected to your phone) for many weeks.
I have had a few of these for several years and found them a great way to stay in touch on longer remote walks. They can send regular GPS updates to a web-based map for people at home, and people at home can contact you if they need.
Although most of these units provide an “emergency” switch most just send an email or SMS to someone you nominate. InReach provides a monitoring service, but if used for emergency communication you need to make sure you understand where the emergency message is sent and the delay this may cause. They also do not have the homing signal as a PLB does. They do allow more detailed messaging in an emergency.

Sat phones
$700-$1500 (+15 up a month connection fee - yearly contracts generally apply
Satellite phones are both amazing and frustrating. They allow you to make calls almost anywhere but cost a lot, chew through batteries and can be a bit tricky to get a call through.
A satellite phone generally looks like 15-year-old mobile phone but they use space-based repeaters.
There are two main types of satellite networks. Ones that have many fast moving satellites (Low Earth Orbit, e.g. Iridium and Globalstar). And the others who may have just a few satellites that always sit in the same part of the sky (Geosynchronous, e.g. Thuraya, Optus). Geosynchronous means you can always know where the satellite is and where to move to get the best view, but you can get stuck in a 'shadow' caused by a large hill or cliff. The Low Earth Orbit provides both better global coverage and fewer 'shadow' areas in rough terrain.
Not all satellite phones allow you to dial 000 (or equivalent) so check with your service provider as what emergency number to use and where the call is actually sent. Many service providers in Australia now do allow 000 for no charge - but it is worth checking.
Call costs vary greatly upwards from $1 a minute. Many also charge you for incoming calls. You can send and receive SMS and many services allow (pretty slow and very expensive) internet access. Even voice mail can cost you a fortune. Battery life is a big issue on these phones so if you are carrying one you will generally want to leave it switched off and organise times to call or receive calls.
In an emergency these phones allow you to explain the exact situation and get some advice. Making a call is not guaranteed especially in narrow valleys or under dense vegetation, but in most open bushland settings they work fine. A satellite phone call does not provide accurate location information so with most phones you will need to tell the emergency operator your exact location. They also do not provide any homing signals.

PLB (Personal Locator Beacon)
$300-$600 (no ongoing fees, the battery in the device needs to be replaced every 5-7 years) A PLB is the most reliable remote area communication system in case of a life-threatening emergency. They are transmitted only and send an “I need serious help now” message via the COSPAS-SARSAT satellite system to the Australian Maritime Safety Authority (AMSA) who will then coordinate the potential rescue. PLBs use much higher transmitting power than systems like SPOT and are therefore much better in getting a signal through tree cover. PLBs actually send two separate signals - one contains your location (if GPS is enabled) as well as your unique identification number (UIN) the other is a homing signal that is used by both air and ground crew to find you.
A PLB should only be activated when there is a threat of grave and imminent danger. Before activating your beacon try dialling 000 on your mobile and other reasonable methods of communications first.
PLBs need to be registered (free) with ASMA. Registration allows them to call you to check that it is not an accidental trigger and to get more information about you, your group and walk - all very helpful when coordinating a rescue. The rescue team will try to cross reference the PLB UIN with any submitted walking plans with local police.
Free or cheap PLB hire is available by some park and police offices. In NSW the Blue Mountains offer a fantastic free service through their TREK program. Tas Parks also provide PLB hire for $40 a week. Neil Fahey provides PLB hire via the post on http://www.bushwalkingblog.com.au/ from $10 a day (including postage).

These devices like a clear view of the sky with as much sky visible as possible. Thankfully they also work in less ideal conditions. Here are some tips to improve reception.
• Keep the antenna vertical (or as directed in instructions) and keep them as far from an object as possible.
• Move to an area with the best view of the sky (avoid the base of cliffs and steep valleys if possible).
• Really dense vegetation can absorb a lot of the signal so try to move to an area with an open canopy.
• Conserve your batteries.

What the future holds for communication in the wilderness is an interesting question. We know that communication is likely to get cheaper, lighter and more reliable. This will have an impact both positive and negative. Currently, BGAN offers broadband speed internet connection in a unit the size of a briefcase, for those with a lot of money to spend. Google’s Project Loon is looking set to offer much cheaper, fast and widely available internet connectivity. It even seems likely that autonomous aircraft (drones) will be able to deliver medicine, books or other stuff to us on request. Check out the work of Matternet, as batteries get better the range and cargo weight limits will grow. I wonder if they will carry our packs for us?? Would you want them to?? There are so many questions worth thinking about before the technology arrives.