and Long-Distance Communication
This page describes some of the types of radio that can be used for survival purposes. There are many different types of radio discussed and the page is quite long. Learning about and acquiring one or more of these types of survival radio would insure that long-distance communication is still possible following a disaster, war, economic collapse, and/or if lost in a remote area.
What's On This Page?
History of Long-Range Communication
Summary of Distances Possible
What Are Radio Waves?
Part 1: Survival Radio for Listening (Receiving) Only
Portable Broadcast Band Radios HOT
Basic Home Made Radios
Valve (Tube) Radio
Part 2: Survival Radio for Transmitting and Receiving
The Spark Gap Transmitter
Amateur (Ham) Radio HOT
Outback HF Radio
Radio Distress Beacons HOT
Underwater (Submarine) Radio
Electromagnetic Pulse (EMP) Attacks
Power Sources for Your Radio
Tasks to Complete HOT
In the modern world we're so used to having long-distance communication that we take it for granted. However most types of long-distance communication rely on vast amounts of high-tech infrastructure, most or all of which will fail in the case of a large-scale disruption to our modern way of life.
Depending on the nature of this disruption, some forms will have much more chance of working than others. Some types of communication, under some circumstances, are guaranteed to fail while other types under other circumstances are guaranteed to remain operational.
This page describes the most important of these communication types, and situations which they will work and not work. It includes both one-way (e.g. listening only) and two way (e.g. listening and talking back) forms of communication. The emphasis is on radio because it's the oldest form (apart from wired telegraphy, see below) and the most useful in major disaster-scale scenarios.
History of Long-Range Communication
Here is a brief history of the types of communication discussed on this page. Some history is useful because it gives an idea of what level of technology is required to be able to use the various communication methods. I've left out any controversial and/or unreliable methods such as telepathy.
Depending on exactly how "long-range" is defined, the first forms of long-range communication were visual systems, such as holding up large flags or creating some structure that could be seen at a long distance. A chain of signal fires, such as seen in the Lord of the Rings movies, is an example of this.
Long-distance communication (without using magic) in "Lord of the Rings".
After that was the invention of wired telegraphy in the 1830s. Wired telegraphy used wires (as does a landline telephone) to transfer Morse code messages over distances greater than 30,000 kilometres by 1851.
After wired telegraphy, the next two big steps were to remove the wires and to allow the use of actual sound (like voice and music) rather than just morse code. The terms "telephone" and "telephony" can be used for either wired or wireless communication. The telephone (using wires, known as wired telephony) was invented and went into commercial use in the 1870s in both England and the USA. It was extremely difficult technologically to lay wired cables across the large oceans, and it was not until 1956 until this was successful with the first transatlantic telephone cable. This was only one year before Sputnik, the first orbiting satellite, was launched (using a modified ICBM) and six years before the first commercial orbiting communications satellite Telstar.
The first commercial radio communications began in 1894. These were wireless telegraphy (Morse code) systems, rather than telephony (voice/sound). The first human voice was transmitted wirelessly (i.e. by radio) in 1900, not long after.
In 1901 Guglielmo Marconi was responsible for the first intercontinental radio broadcast, across the Atlantic Ocean between Canada and England. This was a pretty big deal because it meant that, for the first time, across-the-world communications were possible without having to sail a physical message across the ocean on a ship. Aeroplanes could not fly across the Atlantic until 1919. The first message was quite basic and consisted of the letter "S" in morse code being repeated over and over for four hours. The transmitting antenna had 54 wires, spaced about 1 metre apart on two masts about 50 metres high. In the picture you can see why the antenna poles became known as "masts" — if you squint your eyes it looks more like an old sailing ship than an antenna array.
Transmitting antenna as used for the first intercontinental radio transmission. (Source: MDS975)
The receiving antenna was a 150 metre long wire flown high up on a kite. Marconi got a Nobel Prize for his work, and also got his name better remembered by future generations than most of the pioneers of radio.
Marconi plays the Mamba,
listen to the radio,
don't you remember:
We built this city,
we built this city on rock and roll.
"We Built This City" song by US Band Starship, 1985.
Morse code remained in use for decades after that, mainly because it was capable of getting a message through more difficult conditions of radio reception than voice communication. It played a major role in World War II because of the extra distance capability compared to using voice, and also it was much easier to encrypt messages.
Reference: History of Communication on Wikipedia.
Commercial television began in the 1930s in the USA, England, and Europe. In Australia experimental TV began in the 1930s but mainstream TV was not until 1956. Much of the early history of television is more about patent rights and lawsuits than technical achievements.
Experimental colour TV began in the 1930s. The first mainstream colour broadcasts were in in the 1950s in the USA, though it wasn't until the mid-1960s that colour TV sets were sold there in large numbers. Colour TV was not fully released in Australia until 1975. The show Skippy, which premiered in 1968, was filmed in colour for overseas sales and was the first Australian TV show to be widely popular overseas.
The internet was first developed in the 1970s and 80s by universities funded by the US military. In the 1990s it became widely used in business and in people's homes. The first internet was only text based. Beginning in the early 90s the World Wide Web (WWW) allowed the distribution of text mixed with images (like the web page you're reading now), and then by the late 90s video and other media was also included. YouTube first began in 2005 which is really not that long ago in terms of world history.
Summary of Distances Possible
Here is a summary of some possible distances of radio communication.
||Possible Distance Range (aprox.)
|FM broadcast radio
|AM broadcast radio
||500km at night up to thousands of km at night under ideal conditions
|Shortwave (i.e. HF) radio
|UHF CB without repeaters
||3-10km, more on a high mountain (needs a straight line of sight)
|UHF CB with repeaters
|AM 27 MHz CB radio
||tens of km, occasionally hundreds of km under rare ideal conditions
|SSB 27 MHz CB radio
||tens to hundreds of km depending on conditions, occasionally thousands of km under rare ideal conditions
|Cheap low power walkie talkies
||A few hundred metres
|Better quality walkie talkies
||A few km up to tens of km depending on conditions
|Amateur (ham) HF 20 metre band
|Amateur (ham) HF 40 metre band
|Amateur (ham) HF 80 metre band
||a few thousand kilometres
|Smartphones with no available network towers
||About 100 metres (Wi-Fi range)
|Non-smart mobile phones with no available network towers
||About 100 metres
||About 10 metres for most devices
What Are Radio Waves?
A radio wave is an example of what's called an "electromagnetic wave". Like all electromagnetic waves, all they really are is electric and magnetic fields that change their strength up and down a particular number of times per second (known as the frequency).
Other types of electromagnetic waves are light, gamma rays (such as from nuclear explosions), radiant heat (otherwise known as infrared rays, e.g. when you feel warmth on your hand in front of a fire), micorowaves, X-rays and ultraviolet rays.
In 1820, Danish scientist Hans Christian Ørsted discovered that electric currents create magnetic fields. Based on this idea, in 1824 the first electromagnet was made. In 1831 Michael Faraday and others showed that a changing magnetic field creates electricity, which was known as electromagnetic induction.
A changing electric field will create a changing magnetic field. And a changing magnetic field will create a changing electric field. In the late 1800s, James Clerk Maxwell put these together and realised that the two types of fields could keep creating and re-creating each other. He showed mathematically that they would travel through space like that — as a type of "wave" where the thing that is "waving" up and down is the strength of the fields. He also calculated the speed of these waves based on known electrical and magnetic properties, and found that they would travel at the same speed as light. He therefore concluded that light was an example of an electromagnetic wave. For his discovery of electromagnetic waves and other achievements Maxwell is widely regarded as the third greatest physicist ever after Newton and Einstein.
Below you can see a 3-dimensional representation of an electromagnetic wave. The electric field (purple) and magnetic field (blue) are at right angles to each other and both are at a right angle to the direction the wave travels in. The vertical axis represents electric field strength. The axis that points downwards to the right represents magnetic field strength. The long axis that points upwards to the right is the direction the wave is travelling in, and could represent either distance or time in the same way that a water wave at the beach goes up and down as you look across it (distance) and also it goes up and down in time if you stay in the one spot.
An electromagnetic wave. (Source: University of Alberta)
The speed of light and other electromagnetic waves, including radio waves, in free space is a constant 299,792,458 metres per second (which is close enough to 300,000,000 metres per second or 300,000 kilometres per second). In other materials they travel slower then they do in free space. Air is comparatively not much denser than free space and they don't travel much slower in air than in space — 299,700 km/s (only about 90 km/s slower).
Speed equals distance divided by time (think of a familiar speed unit like kilometres per hour, i.e. distance / time, and this will make sense). This can be rearranged to give time = distance / speed. Which can be used to calculate the time elapsed during one wavelength of an electromagnetic wave, known as the period. The frequency is the number of periods that fit into one second, i.e. frequency f = 1/period, which is the same as f = speed /distance, which is the same as f = 300,000,000 / wavelength in metres. Using this formula you can calculate the frequency of any electromagnetic wave based on the wavelength. The formula can be rearranged to wavelength = 300,000,000 / frequency, to find the wavelength if you already know the frequency. For example, radio station 2JJJ in Sydney transmits at a frequency of 105.7 megahertz (i.e. the electric and magnetic fields are waving up and down 105,700,000 times per second). To calculate the wavelength of 2JJJ in Sydney, using the formula of wavelength = 300,000,000 / 105,700,000 metres gives (using a calculator) 2.84 metres.
The diagram below shows the frequency and wavelength of the different types of electromagnetic waves. Radio waves are at the bottom end of the diagram. The frequency scale is hard to see but starts at 106 at the bottom, which means 1,000,000 Hz (which is also 1000 KHz or 1 MHz, and has a wavelength of 300 metres). It then goes up by multiples of 10, so 107 is 10 MHz (with a wavelength of 30 metres), 108 is 100 MHz (with a wavelength of 3 metres), and so on. Most people are quite surprised that radio waves can be so long.
The Electromagnetic Spectrum. (Source: Wikipedia)
The Carrier Wave
In radio terminology, "carrier wave" usually means a plain, unaltered, electromagnetic wave in the radio frequency range that doesn't contain any information.
The carrier wave is usually represented by a drawing of a sine wave like in the image below. The horizontal scale refers to distance (it can also be thought of as time), and the vertical scale is the intensity of the electric field (or magnetic field) which goes up from zero to full strength and then back down to zero and then into the negative (below the midline) where the field is pointing the other way, and then back again. The number of times per second this happens is called the frequency.
Radio frequency carrier wave. (Source: Electronics All-in-One for Dummies)
If you look at the above wave, it does not contain any information or message. Assuming you had the technology to transmit and receive a wave that looked like that, have a think about how you might alter the wave to be able to send and receive a message of some sort...
Modulation refers to the way the signal information (e.g. someone's voice) is inserted into the plain radio "carrier" wave, so that a message (or radio show, etc.) can be sent and received. The most common types, which you have probably heard of, are AM and FM.
Morse Code a.k.a. "CW"
The simplest type of modulation is to just turn on and off the carrier wave at the transmitter. And then the listening station can detect the wave being turned on and off. This was used in the first radio transmitters to send messages using morse code. For this reason, the term "carrier wave" (abbreviated to CW) is sometimes used to mean sending messages in morse code.
The picture below represents the carrier wave being turned on and off in the pattern that represents the letter "R" in Morse Code, which is usually written as ".-." or dot-dash-dot. Note that the horizontal scale is not accurate in that there would be a lot more oscillations (i.e. cycles or wavings) of the carrier. For example, if the dash lasted for 1/5th of a second, and the carrier frequency was 30 MHz, there would be 30,000,000 / 5 = 6,000,000 up and down wavings — though only 24 are shown since it would be impossible to fix six million up and down cycles onto the image.
The letter "R" in Morse Code. (Source: Louie E. Frenzel, Jr.)
The be able to send real-life sounds over the radio, such as voice or music, the first type of modulation that was developed is called "Amplitude Modulation" or AM.
The word "amplitude" means size, so in amplitude modulation, the size (i.e. strength or level) of the carrier wave is changed (i.e. modulated) to correspond to the shape of the sound waves that are being sent. A microphone is used to convert the moving air particles (i.e. the sound waves) into moving electrical current. The frequency of sound is much less than that of the carrier waves. The human ear under ideal conditions can hear sounds with frequency between 20 Hz and 20,000 Hz. Low frequencies are low bass notes and the high frequencies are high pitched treble notes. However most sound transmitted over the radio has a much more limited range, e.g. from 110 to 4,500 Hz for AM broadcast radio and about 40-7000 Hz for FM. The increased range of FM explains the more hi-fi sound compared to AM radio, and the reason why almost all music stations are on FM now.
When you combine the slower sound (a.k.a. audio) frequency with the carrier (radio) frequency, you get something like this:
AM Radio Modulation. (Source: Electronics Hub)
In the image above, the "Modulating Sine Wave Signal" is the sound wave converted to electricity, and the carrier is the radio frequency wave as before. As for the CW image, the carrier wave here is also shown with a much lower frequency compared to the audio wave — i.e. there would be more waves of the carrier in between each wave of the audio frequency signal.
Historically AM was the first type of modulation to be used (apart from morse code), because it's simpler technology to design and build than any other type of modulation (apart from morse code).
FM stands for "Frequency Modulation" and you can see how it works below, compared to AM. Instead of changing the amplitude (i.e. strength, or height on the graph) of the carrier wave, the frequency is changed. The FM drawing is exaggerated in that the change of frequency would be more subtle than it looks in the image.
AM versus FM radio modulation. (Source: Wikipedia)
Commercial Broadcast Radio (Analogue)
Commercial broadcast radio consists of what is usually called the "AM" and "FM" bands. The AM band is between about 500 and 1600 KHz (which is the same as 0.5 to 1.6 MHz), and AM modulation is used on this band. The FM band goes from about 88 to 108 MHz, and (as you can perhaps now guess....) FM modulation is used on this band.
Commercial Broadcast Radio (Digital)
See here further down the page.
Single-Sideband (SSB, USB and LSB)
In an AM signal, the audio frequency sound waves are combined with the much higher radio frequency carrier wave. When two waves are combined in this way, an effect of this is to create new waves at both the sum and difference of the frequencies of the original waves. That is, combining a 1000 KHz radio carrier wave with a 1 KHz sound wave would create waves with frequencies of 999 KHz and 1001 KHz.
SSB Modulation. (Source: University of Hawaii)
[Optional technical paragraph, click here to skip]: The reason for this can be hard to get your head around, because the two "new" waves of frequencies 999 and 1001 KHz are actually exactly the same thing as the combination of the 1000 KHz wave with the 1 KHz wave, except viewed in another way. Kind of like a more complicated version of a glass being half full is the same as the glass being half empty. If you've heard of the idea that any wave at all, no matter how complicated, can be made up from particular combinations of pure sine waves, it's the same principle as that. Mathematically, you could use the "prosthaphaeresis trigonometric identities" such as sin(A) * cos(B) = [sin(A+B) + sin (A-B)] /2. Which is taught in advanced high school maths and basically says that multiplying two waves together (e.g. an audio wave of frequency A and a carrier wave of frequency B) is the same thing as two waves of frequencies A+B and A-B added together (and halved for conservation of energy). Another way you could think of it is the "beat" frequencies that can be heard when tuning musical instruments — it's the same principle as that but operating the other way around. (Using the equation above backwards, from right to left.) When you play two musical notes of almost the same pitch (like when tuning a guitar for example), you will hear what sounds like just one note of pitch in between the two original notes, and the loudness (amplitude) of the note will vary up and down slowly. In this case the pitch of the note you hear is like the carrier wave, the slowly changing volume (the actual "beat") is like the audio wave that's being sent over the radio, and the frequencies of the two original plucked strings are like the two sidebands (e.g. 999 and 1001 KHz in the example above). The difference between this analogy (and the formula above) and AM radio is that the modulating signal must always be positive, so it's actually (1 + sin (A)) * cos (B), and when you expand that and use the trig formula you get both sidebands and the original carrier frequency. Which is explained even more technically here. It's not so much that the modulation creates the sidebands, although it does, it's more like the sidebands are just there as another way of viewing the modulated signal.
Here is a diagram showing the combined modulated wave on the left, and the sidebands together with the carrier wave on the right. A single pure sine wave of audio frequency (the red line) would combine with the carrier to give the two sidebands as shown below, which would have a particular frequency of exactly the sum and difference of the carrier and the modulating wave (i.e. fc + fm and fc - fm). A real audio signal from a microphone (assuming the only sound wasn't a pure sine wave) consists of a combination of different frequencies. That will give a range of frequencies for the sidebands, like shown in the yellow diagram above.
SSB Modulation. (Source: Principles of Electronic Communication Systems)
So, when using AM, what you get is the plain carrier wave plus two identical (but mirror image in frequency) "sidebands" which is what carries the actual audio signal. The practical outcome of this is that it's possible to remove the carrier itself, and one of the sidebands, and put all of the transmitting power into the one remaining sideband (hence "single" sideband), giving a stronger signal that can be heard over greater distance.
There are two main downsides to using SSB. One is that the receiving equipment must reconstruct the carrier to be able to demodulate the signal (so you can listen to it), so the receivers are considerably more complicated to build and therefore more expensive. The other is that having to artificially add back the carrier means the sound quality is not as good. For both these reasons, standard AM has been used for commercial broadcast stations.
SSB however is used much more often than AM or FM in long distance "DX" amateur (and even CB) radio communications, where it's desirable to maximise the distance you can communicate over versus transmitter power.
SSB is sometimes referred to as USB (upper sideband) or LSB (lower sideband) in order to specify which of the two sidebands is being used. In amateur radio, by convention, USB is used on frequencies above 10.000 MHz and LSB is used on frequencies below that.
With modern transmitting equipment, the choice of which sideband to use is made by turning a switch on your radio. The listener must have their radio switched to the same sideband (LSB or USB) that the signal was transmitted on, otherwise the transmission will sound like a foreign language that can't be understood. Listening to a signal sent using SSB on a plain AM receiving set will also be unintelligible. Listening to an AM signal on a SSB receiver is possible but it will sound better (higher quality) if the receiver is expecting AM. Almost all receivers that can pick up SSB can also be set to AM by turning a switch.
See here for more about SSB.
Part 1: Survival Radio for Listening (Receiving) Only
This part discusses radios you can own that can listen only, without being able to talk (transmit) anything.
Portable Broadcast Band Radios
The easiest, cheapest, and one of the most useful types of radio to have is a small portable "broadcast band" radio, that is, one that can pick up the familiar AM and FM bands that most people listen to. In the 1970s and 80s these were called "transistor radios" meaning that they were not valve radios.
They can be bought very cheaply, carried easily, can pick up the AM band, and almost all modern radios have the FM band as well. Some of them have other bands such as shortwave, or VHF bands which may be called "aircraft" or "TV". The TV on these refers to analogue TV which is no longer being transmitted. And example of such a radio is the Sony ICFS10MK2 which sells for about $35 Australian dollars. Cheaper brands are also available for as little as $5 including postage from China, however a known brand like Sony or Panasonic etc. would be expected to be more reliable and give better reception (i.e. be better at picking up weak and/or far away radio stations). Some radios sold in America have a "weather" band, which as far as I'm aware does not work in Australia.
Click here to browse "Emergency Radio" on Amazon.com.au
Sony ICFS10MK2 Portable AM/FM Battery Operated Radio. (Amazon.com.au link)
The Sony ICFS10MK2 and similar radios run on two AA batteries which can be disposable or rechargeable such as NiMh. There are only a few controls meaning they are easy to operate, with nothing to program, or install, or update so that it will work correctly.
The Sony ICFS10MK2 is known for being a quality radio, with extremely good reception both FM and AM, for it's size and price. It's been discontinued but can still be found. It's now sold as the updated model is the Sony ICF-P26 (Amazon link which claims it ships to Australia) which is probably also very good. The Panasonic equivalent is the RF-P50, which also has mostly extremely good reviews, though people say the Sony has better long range AM reception (which is important for a grid-down situation).
The longest range of reception with one of these is on the AM band in the evening and at night, when interstate stations can be heard in Australia.
The next step up (in price and complexity) from these types of radios would be one which can also receive the shortwave band.
Sangean MMR-77 Portable Crank and Battery Powered Emergency Radio.
The Sangean portable radio has a built-in hand crank to recharge the Ni-MH battery, perfect for emergency situations. It features FM/AM bands for your favourite radio stations and is powered by dynamo, battery or AC power adapter. It has an illumination lamp, charging and tuning LED indicators and is water resistant. The built in Ni-MH battery pack is replaceable, which is important since rechargeable batteries generally only last about 5 years. Many models of small portable crank powered radios are quite cheap and nasty, however this has a reputation as a solid, quality made radio.
Purchase from Amazon.com.au
Purchase from Amazon (US) (lots of reviews, probably doesn't post to Australia, though they sometimes may, they used to a few years ago?)
Detailed review of the Sangean MMR-77 with lots of pictures (external link)
Digital radio uses digital forms of modulation, where a stream of bits (on or off states representing ones and zeros in binary) is coded and then decoded using computer technology. The receivers are more expensive than analogue ones, the possible distance range is less, and the receivers use more power (meaning shorter battery life).
Often this type of digital radio is referred to as "DAB" or "DAB+" (with the "plus" version being the newest standard), which stands for Digital Audio Broadcasting. DAB+ is used in most countries, except for (according to Wikipedia in July 2020) Ireland, UK, Romania and Brunei who still use a significant number of DAB (non-plus-version) services. And except for North America, which uses a different system/standard called "HD Radio".
The channels are usually (and perhaps always?) free-to-air (like traditional analogue radio), meaning you don't have to pay for a subscription.
There is perhaps some chance that in a crisis situation, digital radio broadcasts are still working where analogue radio and other forms of communication (e.g. TV, the internet, and the phone network) are not. In that event it would be extremely beneficial to have a digital radio. However it seems to me this chance is fairly small.
ACMA Digital Radio FAQ
Digital Radio on Wikipedia
View digital radios for sale on Amazon.com.au
The crystal radio is the simplest and most basic type of radio in terms of it's design and the number of parts needed for construction. It's also the only type of radio (that I know of) which can be built entirely from simple household items, without any specialised electronic parts.
It's also the only type of radio I can think of which runs without any power source. I don't mean that it has a solar panel or something local to power it, I mean there is no power source as such in the circuit at all. I've asked a lot of students to try and think of where the electricity to power the earphone comes from, and almost no-one thinks of the answer. See if you can. (The answer is given below.) As a hint, there is no speaker, the crystal radio only uses a special "high-impedance" earphone which requires very little electrical power, and even that isn't very loud.
Crystal Radio Kit. (Source: De Radio Verzamelaar)
Here is a crystal radio kit from the 1970s. The kit ones you can buy now probably aren't much different except probably less plastic and more cardboard. This particular one has the circuit diagram (i.e. "schematic") printed onto the radio itself, so it's a good one to learn from the picture. There are very few components, and you can see them all on the plastic baseboard, except for the underside of the variable capacitor which is the business end of the tuning knob. It's marked as VC for variable capacitor on the radio above. The other parts are the earphone, a diode which is the "crystal" in this radio, and a coil of wire wrapped around a rod made out of ferrite. Ferrite is used because it has high magnetic permeability (meaning it is easily magnetised) and low electrical conductivity, though other more ordinary materials can be used, even a toilet roll. The diode needs to be germanium, not silicon, because of the very low power of the signal in the crystal radio. The only other parts are wires to connect the individual parts, and also to function as the long wire antenna and a ground wire to connect the radio set to earth (i.e. the actual earth as in the ground outside). The antenna and ground wires are not shown on this radio but they would connect to the terminals on the left. This radio has two options for the antenna connection depending on how long or short the antenna wire is.
How It Works
It's not that difficult to understand the basics of the theory behind how a crystal radio works. Read the sections on carrier waves and AM modulation first if you haven't already.
Below is a basic schematic (circuit diagram) for a crystal radio. Note how it matches the actual radio in the picture above. The parallel lines with an arrow through them, in the middle of the diagram, is the variable capacitor.
Crystal Radio Schematic. (Source: OldRadios)
A capacitor is an electronic component that blocks low frequencies and allows high frequencies to pass through it. A coil (often called an inductor) has the opposite effect, it passes low frequencies and blocks high frequencies. By using a capacitor and a coil connected together like they are here, both the high and low frequencies are blocked and only frequencies within a particular very narrow range are allowed to pass through. This will have the effect of selecting a particular radio frequency. This is known as a tuned circuit. Because in our radio the capacitor is variable, it's value (technically called its capacitance) will change as you turn the knob, which means the exact frequency that is allowed to pass through can be changed so you can tune in a radio station.
What you would have after the tuned circuit is something very like the waveform below (also shown in the section on AM modulation).
AM Radio Modulation. (Source: Electronics Hub)
Connecting the signal above directly to an earphone will not produce any sound, because the fast radio frequency (RF) oscillations (i.e. the signal going up and down at RF frequencies such as 1,000,000 times per second) are far too fast for the earphone to physically keep up with. This is where the crystal comes in. Connecting a crystal such as a diode into the circuit has the effect of passing electricity in one direction only and not in the other direction. This is called "detecting" the signal, and results in a signal like shown in graph B below in the wires after the crystal/diode detector.
Because the earphone is too slow to move back and forth with the fast RF oscillations (the jagged peaks on the graph), what happens is as it tries to follow them, it ends up moving like the waveform in graph C below, which is basically the audio signal. Close enough that you can hear it in the earphone.
AM Detection in a Crystal Radio. (Source: Wikipedia)
An optional improvement often seen is to connect an extra capacitor (a fixed value one this time, not a variable one) across the earphones, which will short out (i.e. remove) the high frequency RF by letting it pass through the capacitor, and leave the low frequency audio (AF) remaining. So the signal will look like graph C even before it gets to the earphones, improving the sound.
The tuning is quite primitive compared to more modern and sophisticated radio receiver circuits. That and the low sensitivity mean that usually only one or maybe two stations can be heard on a crystal set.
Historically, many people used crystal radios because anything more elaborate was too expensive. In the early days of radio, from about 1900-1930, a radio was an extremely expensive item and could cost as much as a house or an "automobile". Therefore many people built their own. Crystal radios were the most popular type of radio until the mid 1920s.
There are currently three main uses for a crystal radio:
- To learn about radio theory and understand how a radio receiver works.
- To listen to the radio when there is no better technology available, not even a basic battery powered radio receiver. This was done by soldiers in the trenches and in POW camps in World War II.
- As a hobby/game to try and make the best possible radio that uses no power source.
The answer to the question above, where does the power come from to drive the earphone (so you can hear something in it), is that it comes from the radio waves themselves. Large amounts of power are used at the transmitting station, which go out into the "airwaves" i.e. the radio waves, and a tiny fraction of this power is available at every place close enough to the transmitting station to be able to pick up a signal. Because there is no amplifier in a crystal set, not even a very basic one built into the radio circuit, the received signal needs to be reasonably strong, and generally only strong local AM broadcast stations can be heard on a crystal radio set.
If you're interested in building radios from scratch, you could start with a crystal set and then gradually increase to more complicated receivers which can hear more stations and do more things (e.g. power a speaker). If you want to build transmitters, this is also possible. Building your own radio transmitters, other than extremely low power / short-range transmitters, will require an amateur radio licence.
The great disadvantage of the crystal radio is that they aren't very good radios. Due to having no power (other than the radio waves themselves) and such a basic design, they can only pick up a small number of very close and strong AM radio stations. Since in a grid-down type of situation, there may not be many radio stations left on the air, it would be much better to have a more powerful radio which can recieve distant stations.
Basic Home Made Radios
Other than the crystal set (above), there are many improvements that can be made by adding extra components, and changing the circuit around to give greater performance.
Since electronic equipment is so cheap compared to how it used to be, there is much less practical reason to build your own radio gear from scratch, apart from education and being interested in it. It's also possible to buy old gear and then restore or modify it.
More to be added later.
You can find more here.
One Tube Regenerative Receiver NEW
The one tube regenerative radio receiver is another simple radio which can be built at home. This radio uses a "tube", also known as a "valve" (or "thermionic valve"). They are DIY (do it yourself) radios and you have to either build one from scratch, build one from a kit of parts (if you can find one), or buy one already built by another hobbyist.
The one tube regenerative receiver has much better reception than a crystal radio. Apparently a well built one is quite good even compared to modern radio technology. Like many DIY projects, they are easy to build, but somewhat of an art to build a really good one.
Unlike most valve (i.e. tube) radios, only low voltages are required, so it can run from batteries. Unlike any non-tube (i.e. solid-state i.e. semiconductor based) radio, they are generally safe from EMP, though one attached to a really long wire antenna may still be affected.
Look here for more.
With shortwave radio you can listen to international broadcasts (that is, transmissions from other countries) and you can listen to amateur radio operators (both local and international). In a large-scale grid-down situation, there may still be amateur and commercial transmissions coming from other countries (who may still have grid power) and also from more local amateur ("ham") radio operators who may have their own off-grid power. This is in contrast to the internet and the phone network, which will cease to function when there is no more electricity supply grid in a large enough area around you (e.g. your city) — especially if the mains power loss lasts long enough for any backup generators or UPS at phone exchanges, ISPs, etc., to run out of fuel and/or battery power.
"Shortwave radio" usually refers to listening to frequencies between the AM commercial broadcast band (which ends at about 1.6 MHz) and 30 MHz, which is also called the HF band. The information about bands for amateur radio applies here equally, except that when listening (and not transmitting) it's legal to listen on any frequency you like, not just the particular frequency ranges allowed for licensed amateur radio operators to transmit on. The only exception is that in Australia it's illegal to listen in on telephone conversations, as in conversations between people using the actual telephone network. This is extremely unlikely in the shortwave band, but occasionally possible in the higher frequency bands like VHF and UHF, largely due to cheap landline-connectable "cordless" home phones which use radio between the handset and the part that plugs into the wall.
Most large countries have official shortwave stations with very powerful transmitters, vastly more so than what's allowed for ordinary citizens such as amateurs. This means that these stations are much easier to pick up than radio signals sent by private individuals (e.g. amateurs), and the radios and antennas you need are much simpler (and cheaper). The national stations are often named quite simply, based on their countries, like "Radio Australia" or "China Radio International".
These shortwave radio stations can be heard right across the world with only fairly modest radio receiving equipment and constitute perhaps the most likely source of world information when your own country's communications and/or electrical grid is down, such as is likely to happen in a severe collapse or war.
Another likely source would be listening to amateur radio operators, either using amateur radio equipment or shortwave radio receivers. Shortwave radio receivers can pick up the long-distance HF amateur bands — though on HF most amateurs use the SSB mode for voice, so you would need a shortwave set that has SSB. You also need an SSB set to hear morse code (CW) transmissions. These are available but are more expensive than ones which only have AM (and maybe also FM).
Unfortunately some countries, most notably Russia, are ceasing to operate their national shortwave radio services and changing to internet based information services, which will not be of much use in a severe collapse or war.
Click here for a list of countries with shortwave radio services.
NEW: Sadly, Radio Australia terminated shortwave radio broadcasting effective 31 January 2017. Though in many locations that aren't too remote you can still hear local (if there are any) and maybe (depending on your location) interstate radio stations within Australia in the evenings and at night on broadcast AM radio. More here and here. Nick Xenophon is hoping to reinstate Australia's shortwave radio service.
NEW: Shortwave Radio Equipment
Unfortunately it's getting somewhat harder to find new shortwave radios, as many models are being discontinued and not replaced. This is because the internet has replaced radio for a lot of communications, however in a large-scale grid-down situation the internet isn't going to be available. There are still many models available, though not as many as in previous years, and the number is gradually shrinking. There are still a great many available secondhand, perhaps more than ever before as people shift their interest to digital communications (smartphones and the internet).
Typical Shortwave Radio — C. Crane "CC Skywave" model. Amazon link (Claims to ship to Australia).
Shortwave Radio with SSB — Sony ICF-SW7600GX model. Amazon link here or here (Claims to ship to Australia). Apparently these are discontinued with no replacement so they may not be available new for much longer.
You can see some pictures of more expensive higher-quality communications receivers here and here. Most of these aren't really portable radios, though a lot of them will work on 12 volts (like from a car battery). Note that a few of these images will be transceivers (which can transmit and receive). You can usually tell the difference by looking for a microphone socket on the front panel, which will be a large-ish round socket with several holes or pins inside it, unlike a headphone socket which is just one hole for a standard headphone plug. Most of these types of receivers cost around $1000 and up for a new radio and a few hundred and up for a secondhand radio.
Coming soon - more info on equipment.
Shortwave Radio Links
Shortwave Listeners Delight
The Australian Shortwave Radio Journal
Milcom Monitoring Post
International Shortwave Broadcast Guide: Winter 2015-2016
Prime Time Shortwave
How to Listen to Real Spy Broadcasts Right Now
Secret Cold War Radio Stations Still Broadcast
HFU HF Underground - Shortwave Pirate Radio Forums
Huge List of Shortwave Radio Links by VK5VKA
(Police, Ambulance, Fire, etc)
Still under construction...
A scanner is a radio receiver that can automatically tune, or scan, two or more discrete frequencies, stopping when it finds a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases.
The function of scanning could be applied to any type of radio receiver. However the term "scanner" is usually used to mean radios that receive in the VHF and UHF bands (as opposed to HF/shortwave) and can scan across many frequencies.
Over the last few decades, scanners have been used to listen to police, fire, ambulance and other communications. However due to the increasing use of encrypted digital modes (of modulation) some of these can no longer be heard. This is especially true of police radio in capital cities, which is almost all (perhaps all, I'll update this later) encrypted now. Some rural towns still have unencrypted police radio as far as I know. Ambulance and Fire are still unencrypted as far as I know.
In an emergency situation it can be very useful to hear what is happening from these types of channels.
Most scanners are also capable of receiving (not transmitting) the UHF CB radio band and the VHF and UHF ham radio bands. Some of them can also hear the commercial broadcast FM radio band (i.e. the one with radio stations like 2JJJ and 2MMM etc).
If you buy a scanner and can't hear much on it, the biggest weakness is probably the antenna. Adding an external base station type of antenna would give significantly better reception, meaning you could hear more signals and signals from further away.
Analogue Versus Digital
If you buy a much older scanner, or a cheap new one, it will only be able to receive analogue modes (like AM and FM). The newer more expensive ones can also receive digital modes, which means you can hear more things, though analogue FM and even AM are still used a fair bit.
Scanning the NSW GRN (Government Radio Network).
In Sydney, the Government Radio Network (GRN) is used for police, fire, ambulance, and many other services. (Note that the police are encrypted now).
Only a few scanners are capable of receiving the NSW GRN, and they need to be programmed to do so. The scanner needs to be able to receive APCO P25 transmissions. According to nwsgrn.com, there's only one currently sold model which can do it, the Uniden UBCD396XT, which is a handheld model. There are a couple of slightly older models which also can scan the NSW GRN, the UBCD996T (base/mobile) and the UBCD396T (handheld) scanners.
Also there are the Radio Shack/GRE PRO-96, and the DSE (i.e. Dick Smith) DTS-96, which are almost the exact same radio. These can be found second hand for around $150-200. The programming may be harder on these than the Uniden ones. I think that originally it was only possible with additional PC computer software and a cable to connect the scanner to your PC, and then later changes to the GRN meant that it could be done via the scanner itself (without needing a computer) — but will confirm this later.
There may be other models but these are the only ones I know of.
I'll update this later with some information on programming these scanners for the NSW GRN.
Valve (Tube) Radio
Vacuum tubes (a.k.a. thermionic valves) were used before "solid state" components like diodes and transistors became available in the 1960s and 70s. They're usually called "valves" in England, "tubes" in the USA, and either in Australia, with "valve" being the original Australian term and "tube" being used more recently as the world and our country becomes more Americanized [sic].
Valves are still used in a few applications: Hi-fi sound systems, guitar amplifiers, collectors of vintage gear, and by some people concerned with EMP. Valve electronics is vastly less susceptible to damage from EMP than newer gear.
Valve radio equipment is available for both just listening (the vast majority of valve radios that were made) and also for transmitting (both commercial and amateur equipment). Popular high-quality brands of valve amateur transceivers were Heathkit, Drake, and Collins.
Read here about using tube radio for survivalist communications.
Part 2: Survival Radio for Transmitting and Receiving
This part discusses radios that you can own which can both receive and transmit.
The Spark Gap Transmitter
The most basic type of radio transmitter is the spark gap transmitter. It can only be used for morse code but is by far the easiest to construct from scratch out of basic electronic components. The spark gap transmitter was historically the first type of transmitter, e.g. as used here.
These are available, often sold in pairs, from many electronic retail shops. They require no license and are only capable of short range communications, perhaps up to a few hundred metres, more in ideal conditions (like both of you high up on hills).
CB (Citizens Band) Radio
This is a form of two way radio (meaning transmit and receive) that was most popular in the mid-late 1970s. Mobile CB, meaning CB sets installed in cars, was very popular. You can see it used in the 1977 movie "Smokey and the Bandit", and in "The Dukes of Hazzard".
CB radio does not require a license to operate in Australia (and in many other countries). There used to be a requirement for the operator (e.g. you) to pay for a license, however it was never seriously policed and was dropped completely in 1994. The current licensing system for CB radio is called a "class license" which means the radio set itself is licensed (by the manufacturer conforming to government regulations in the design and manufacture of the radio), and no further license is required to operate the radio. This also means that to stay legal, the radio must not be modified, and only approved radios may be legally used on the CB bands. Approved radios will have been made to comply with laws that limit the maximum transmitting power. They also are limited to a fixed number of specific frequencies (i.e. channels). The number of channels can be changed by the government periodically e.g. in Australia, the UHF CB band was increased from 40 to 80 channels on 27 May 2011. A few channels are designated as emergency channels and it is illegal to transmit on these without a valid reason.
In Australia there are two types of CB radio, UHF and HF. The radio sets themselves are different, i.e. a UHF set will not work on the HF band and vice versa. UHF is newer and by far the most popular. HF is the older system and is also known as "27 megahertz". UHF stands for "Ultra-High Frequency" and HF for "High Frequency". See here for Australian CB radio history.
The current Australian UHF CB band has existed since 27 May 2011 and consists of 80 channels from 476.4250 MHz to 477.4125 MHz. The type of modulation is analogue FM. Older CB radios can only operate on the older 40 channels. The older 40 channel radios will become illegal to transmit with after 30 June 2017. Both systems use the same frequencies for the first 40 channels. In the new 80 channel system, the new channels 41-80 fit in between the first 40 channels, which means there is only half as much "bandwidth" for each channel. Another way of saying this is that the new 80 channel sets transmit a signal that is half as "wide" in terms of frequency. In the 40 channel band plan, the channels are spaced at 0.025 MHz (i.e. 25 kilohertz or KHz) apart. In the 80 channel band plan, the channels are 0.0125 MHz (i.e. 12.5 KHz) apart, i.e. they are half as "wide". If you use an older 40 channel set to listen to people talking on an 80 channel set, you will still hear them except not as loud as if you were listening on an 80 channel set. (Because the 80 channel set is transmitting a narrower signal than the 40 channel set is expecting.) If you talk on a 40 channel set, there is the potential for the wider signal to interfere with the new channels that have frequencies on either side of the channel you're talking on, which is the reason why it's going to become illegal. They didn't make it illegal straight away so people had a few years to upgrade to newer radios.
Uniden UH8020S 80 Channel UHF CB Radio. (Source: Transport and Logistics News)
HF (27 megahertz) CB
The older type of CB in Australia is usually called "27 megahertz" after the frequency range that it uses. As far as I can tell it's the only type allowed in the USA.
Most 27 MHz sets used AM modulation and had a power limit of 4 watts. Some more expensive sets use SSB (single sideband) modulation which gives a greater possible distance range and the legal power limit is 12 watts. Sets which have SSB (at least almost all of them, and probably all of them) also have AM. I think there used to be license requirements for SSB sets, however as far as I can tell this is no longer the case. If you use an AM only set to listen to people talking on sideband, their voice will be unintelligible, like listening to another language which used to be called "duck talk".
The 27 MHz CB band has a wavelength of 11 metres and is very similar in characteristics to the 10 metre amateur (ham) radio band.
Shown below is a basic AM only 27 MHz CB radio designed for the Australian market:
GME TX2720 27 MHz AM CB Radio. (Source: GME)
It is still possible to buy new sets in Australia, although they are getting harder to find, and only seem to be AM rather than SSB. There are heaps of sets available second hand
(both AM and SSB)
which still work perfectly well. Secondhand AM only sets can be bought quite cheaply (less than $100 and perhaps less than $50).
I think (I'll confirm this later) that the USA 27 MHz CB channel frequencies are the same as the Australian ones, meaning that you can use a 27 MHz CB radio made for the USA here in Australia.: YES, they are identical. Comparing here and here, all 40 US and Australian 27 MHz CB frequencies are exactly the same. This means that a 27 MHz CB from the USA will work in Australia. The only thing to watch is if it's called a "base station" model, it probably runs on 120 volt mains power. A "mobile" model will normally runs on 12 volts and will work just as well inside a house or anywhere (it doesn't need to be in a vehicle, "mobile" just means it could run in one).
A 27 megahertz SSB set with a really good antenna is capable of the longest unassisted (i.e. without using repeaters) distance range of any of the CB radios. And probably the longest range of any transmitting device that's legal to own and to transmit on without a radio license.
27 MHz CB Discussion on Whirlpool
Shown below is a 27 MHz AM/SSB CB radio. You can tell it has SSB by the presence of the switch (on the left) that says USB, AM, and LSB. It has a built-in SWR meter.
Pearce-Simpson Super Lion Mark II 27 MHz AM/SSB CB Radio. (Source: YouTube)
There are a few classes of marine radio. One is similar to the 27 MHz CB band, however (I think) licenses are required. To be updated shortly....
I read that there have been a lot of crackdowns on people using marine radios illegally, and this is one of the few cases where the ACMA has taken a lot of action against people for "pirate" radio operation. Some survivalist literature recommends for people a long way inland to buy marine radio equipment on the grounds that hardly anyone near them will have marine radio, and after a collapse of society they can use it for semi-secure local communications with friends who also have the same types of radio gear.
Amateur (Ham) Radio
Amateur radio (also known as ham radio) is the most "serious" of the types of radio transmitting available to ordinary people, meaning there is a higher level of investment and education involved, and a correspondingly greater number of things you can do with it, and greater ranges of distance that can be communicated over.
Using HF amateur radio equipment it's possible to communicate worldwide without relying on any third parties such as ISPs or telephone companies or satellites or overland cables or undersea cables or any of the vast networks of supporting infrastructure that these things need to function. All that is needed is your equipment and that of the person you're talking to, and electricity to power the radios (which can of course be off-grid electricity such as from solar panels).
Mobile phones (irrespective of whether you want to use the internet or just the phone network itself) are not like this and can only function when there are functioning base towers (and the rest of the telephone system) for them to communicate with anything. Which means that in the future, in an emergency or collapse situation when the phone network (and internet and/or power, etc) is no longer functioning, mobile phones will be useless and amateur radio will be going strong (provided there is electricity available locally and the radios haven't been destroyed by EMP or any other act of war or damage).
Although worldwide communication is possible, it's not reliable/repeatable in the way that a telephone call is reliable, where you can dial up any person in any country you like at any time. More localised communication, such as around Australia / interstate, is much easier and more reliable. Atmospheric conditions make a huge difference to "propagation" of long distance radio signals, and this includes what time of day or night, what season, and what part of the Sun's 11-year sunspot cycle it's up to.
The term "amateur" implies not used for commercial purposes, i.e. people in their spare time and not for profit. A license is required in Australia and most other countries in order to transmit. No license is required to listen to amateur radio transmissions with the right type of radio receiving gear, such as a shortwave receiver or a scanner.
It's illegal in Australia to own amateur radio transceivers or transmitters without a license, although its extremely unlikely (as far as I know, probably impossible) to be prosecuted for this unless you try to use it to transmit while unlicensed. Especially if you have a semi-valid reason for owning it i.e. you're studying to get your license. Even most people who transmit on the amateur bands illegally will simply be told to get off the air by other amateurs (who can easily tell if someone is unlicensed), and otherwise ignored, which results in most people getting bored of their pirate radio operations pretty fast. Doing something really dumb like transmitting over the top of police frequencies or a major commercial TV station may bring the authorities down on you like a SWAT team drug bust from a movie.
There are several different "bands", i.e. ranges of frequencies that amateurs are allowed to transmit on. These can be referred to by either their approximate frequency or their wavelength. (See here for how frequency relates to wavelength). See here for more information.
Each band has its own characteristics of how the signal will travel through the atmosphere. This means that the distances possible and the times of day and atmospheric conditions that give the best communications are somewhat unique to each band. Bands close together (e.g. 17 and 20 metres) will be somewhat similar. In general, the low frequency (long wavelength in metres) bands are good for across-Australia communications, including interstate communications, especially in the evening and night. The middle range HF bands like 20 metres are good internationally (because signals of this wavelength can bounce off the upper atmosphere and re-appear much of the way around the world). Higher frequencies (shorter wavelengths) like 28 MHz (which is 10 metres) are best for local communications.
This table shows the most popular amateur radio bands. The table was taken from eHam.net and modified to the Australian frequency ranges current as of January 2016.
||1.8 - 1.875
||3.5 - 3.7
3.776 - 3.8
|Night and local day
||7.0 - 7.3
||Night and local day
||10.1 - 10.15
||Like 40 metres but longer range
||14.0 - 14.350
||World wide day and night
||18.068 - 18.168
||World wide day and night
||21.0 - 21.450
||Primarily a daytime band
||24.890 - 24.990
||Primarily a daytime band
||28.0 - 29.70
||Daytime during sunspot highs
||50 - 52
52 - 54
|Local to world-wide
||144 - 148
||Local and medium distance
||430 - 450
* Bands in bold font are the most popular. This is the approximate wavelength of the radio waves in metres. To convert exactly between a frequency in hertz (symbol Hz) and a wavelength in metres use the formula wavelength = 300,000,000 / frequency. One megahertz (MHz) is 1,000,000 Hz. So for example, 21.450 Mhz is 21,450,000 Hz and its wavelength is 300,000,000 / 21,450,000 = 13.98 metres. To convert the other way, use frequency = 300,000,000 / wavelength. The value of 300,000,000 (i.e. 300 million) is the speed of light in metres per second.
** This column shows which Australian license types are allowed to use the bands. A = Advanced License, S = Standard License, F = Foundation License. Many other countries are similar but not identical.
*** Based on the physical/electrical characteristics of the band and how the radio waves travel through the atmosphere. It should be noted that band conditions vary for many reasons and thus all of these bands can at times take on the characteristics of others. See the section on Propagation. This table should be considered a general guideline.
The Australian amateur bands are shown here (PDF) in detail. If that link is expired, you can probably find it here under "Current Band Plans" in "Files for Download" near the bottom of the page.
HF stands for "High Frequency" and refers specifically to the part of the radio spectrum between frequencies of 3 and 30 megahertz. Sometimes it's called "shortwave", usually in the context of listening rather than transmitting. In the old days of radio, the lower frequencies were much more commonly used, and they talked about longwave (LW) a.k.a. low frequency or LF, medium wave (MW) which can be also (but usually isn't) called medium frequency or MF , and High Frequency (HF) a.k.a. shortwave (SW).
HF is the best part of the radio spectrum for really long-distance (such as international) communication. This is because the upper atmosphere of the Earth acts like a reflector for some of the radio waves in this range, and they can travel out into the air and then bounce back down towards the ground very far away, travelling around the curvature of the Earth. This is known as a skywave.
The most popular HF bands are the 80 metre band (3.5 MHz), the 40 metre band (7 MHz), the 20 metre band (14 MHz), 15 metre (21 MHz) and 10 metre (28 MHz).
The best amateur band for long distance ("DX") communication, such as round-the-world / international communication is the 20 metre band. You need at least a Standard License to transmit on the 20 metre band in Australia.
There's also a 160 metre (1800 KHz, 1.8 MHz) band, which technically isn't HF (it's medium wave or MF) but is often included as if it is part of HF, and many HF transceivers can operate on 160 metres. You need an Advanced License to transmit on the 160 metre band in Australia.
Since the higher than high frequency parts of the radio spectrum were not really used until after World War II, the newer names sound kind of silly, like "Very High Frequency" (VHF), "Ultra High Frequency" (UHF), "Super High Frequency" (SHF), and so on.
Repeaters are automatically-operated (unmanned) radio stations (usually with a large tower antenna) that listen for transmissions on a particular frequency and then re-transmit the same thing on a different frequency but from a better physical location and/or with a higher power level and/or using a better antenna than the original transmission.
The purpose of a repeater is that you can talk to people over a much increased geographical area using the better location and antenna and/or higher transmitting power of the repeater.
They are usually located on high hills or mountaintops which gives a much better signal on the VHF and UHF bands, since these bands work best when there's a relatively clear line of sight from transmitter to receiver. Therefore repeaters are much more commonly used on the VHF (2 metre) and UHF (70 centimetre) bands than on HF, though a few HF repeaters do exist around 29 MHz (10 metres). The middle and lower-range HF frequencies can achieve long distance communications without repeaters.
Repeaters can be used in amateur/ham radio, CB radio, and other types of radio e.g. commercial radio. A lot of repeaters use special tones (e.g. CTCSS) to access them, which means some older radios without these features aren't able to use many repeaters.
To use a repeater, your radio needs to be set to transmit on a different frequency to the one it's listening on. This is achieved on modern radios through the programming settings, usually using an "offest frequency" which is the difference between the transmit and receive frequencies.
The disadvantage of using repeaters is that in some emergency situations, such as when the power grid is down, the repeater(s) may also be down and unavailable for use.
WIA Repeater Page
UK Repeater Page (Good info)
Amateur Radio: What You Need - The Minimum
The least you need to get listening is a shortwave radio that's capable of picking up SSB for the HF bands), and/or a scanner or other receiver for VHF and UHF. Also an antenna of some sort, though the antenna requirements for listening are vastly more relaxed than for transmitting. For HF/shortwave a really long wire strung as high up as you can easily manage will work well, and even better if you attach a ground wire to your radio.
The least you need for transmitting (talking) on VHF and/or UHF is:
- A license — see below.
- A handheld transceiver. These can be bought for as little as $50 new (perhaps less even), e.g. the Baofeng brand models. [View Baofeng transceivers on Amazon.com.au]
- Probably, a better screw-in handheld antenna than the one that comes included with the above transceiver (such as an extendible/telescopic whip which is much longer than the short "rubber duck" antennas). Almost certainly if you have one of the cheap $50 ones.
- The next step after that to improve your range would be a better non-handheld antenna.
The least you need for transmitting (talking) on HF is:
- A license — see below.
- Either a transceiver, or a separate transmitter and receiver. The cheapest good quality HF transceivers new are about $1000 AUD in 2016. Examples would be the ICOM IC-718 and the Yaesu FT-450D. Good quality secondhand transceivers can be found for $500 AUD and even a bit under if you look around. Searching for Yaesu FT, Kenwood TS, and ICOM IC in places that sell secondhand radios will find many models and you can type the model name followed by "eham" into a search engine to read reviews of the radio.
- Unless your transceiver accepts 240 volt mains power (many don't), a 12 to 13.8 volt high current (i.e. amps) power supply. The current required will depend on how many watts of power your transmitter can output. Around $200-300+ AUD for a 20-30+ amp one that can power a 100+ watt transceiver for long distance communications.
- An antenna. Antennas for HF can be a few metes in size up to 80 metres long, with the longer wavelength bands needing longer antennas.
- A means of measuring the SWR.
- Unless your antenna is really well built (and optionally even if it is), an antenna tuner.
- A microphone and/or morse code key (these are the easiest/cheapest items to obtain on the list).
You can browse new amateur radio equipment here at Andrews Communications. This is debatable but perhaps the most popular brands are Yaesu, Kenwood, and Icom.
Most of the transceiver models are either HF or VHF/UHF, or for the higher frequency bands perhaps just a single band only like 2 metres or 70 cm. Many but not all the HF radios include the 160 metre band. A few HF radios include the 6 metre band, perhaps using an optional plug-in module. A very few radios cover HF, VHF and UHF.
When looking for transceivers, "all modes" in the product description means all common types of modulation such as AM, FM, SSB, etc.
Amateur Radio Licensing
It's become a lot easier to get an amateur radio license than it used to be. There are currently three levels of license offered in Australia: Foundation, Standard, and Advanced. The current system started on Wednesday 19 October 2005.
For the Foundation License, you need to sit an exam that covers basic radio regulations and operating procedures, and a practical exam operating a radio. Foundation License holders are limited to 10 watts of transmitter power, which is quite low for some of the bands.
For the Standard License, you need the above plus another exam covering radio and electronics theory which is expected to take 20-30 hours of study to pass. Upgrading to the Standard License means you can transmit on more bands (i.e. frequency ranges), use more transmitting power (up to 100 watts on HF), and build or modify your own radio gear.
The Advanced License has a more difficult radio and electronics theory exam which is expected to take 50-100 hours of study to pass. The advanced license allows still more bands and more transmitting power, up to 400 watts on HF.
Although this may seem difficult, this license structure is actually much easier to qualify for than the previous one, which was relatively unchanged from 1975-2005. The "Novice" license was introduced in 1975. This used to be the easiest license to get, and required a regulations exam, a theory exam (which is similar or identical to the current Standard theory exam), and a morse code exam; sending and receiving at 5 words per minute. And after all that effort, you were still more limited in what bands you could use than with a current Standard Licence. The previous full/unrestricted amateur license was similar to the current Advanced license except you also had to pass a morse code exam at 10 WPM (words per minute), which was originally 12 WPM when it was introduced in 1924. There was also a "Limited" license, introduced in 1954, for which you had to pass the regulations and the full/advanced/difficult theory exam, but no morse code was required, and you could only use the VHF and higher bands. Which was the same level of difficulty as the current Advanced license (i.e. the hard theory and no morse) but you couldn't use any of the HF bands which are the ones that almost all long-distance (interstate and international) calls are made on.
Licensed amateur radio operators have their details, including name and address, stored in a publicly accessible register. If you're concerned about privacy, the only legal way to not have your address published publically is to have a post office (PO) box and write your PO box address on the forms as the address of your amateur radio station. The cost of a PO box in Australia depends on which post office, and starts from about $126 a year, which is more than double the $51 annual renewal cost of an amateur radio license.
Shown below is a simple looking amateur radio station, G0RTN in the United Kingdom. The laptop computer is optional but useful. The transceiver (bottom left) is an ICOM IC-7400. The current version of this radio is the IC-7410 which costs $2000 AUD in 2016. Above that is an antenna tuner made by MFJ. The operator can talk using the handheld microphone in front of the transceiver. On the right behind the mouse is a morse code paddle, which is similar to a morse code key except it's moved side to side rather than pressed down. It looks like a printer behind the laptop. The two critical components that aren't shown in the picture are the antenna and the power supply for the IC-7400.
Amateur Radio Station G0RTN in the UK. (Source: Radioaficion.com)
Below is a more established and higher budget looking station DJ4PI in Germany. The radio in the bottom left is an ICOM IC-7800 which is one of the most high-tech and expensive ham radios available. The current model is the IC-7851 which costs $15,000 AUD new in 2016. You definitely don't need one of these to get started, any more than you need the latest model Ferrari to drive you around. The radio in the middle with the orange LCD displays looks like an ICOM IC-775, which is worth about $1500 AUD second hand.
Amateur Radio Station DJ4PI in Germany. (Source: Wikipedia)
In case you don't like mess, below is a nice looking amateur radio station using vintage 1960s tube/valve operated equipment, as opposed to solid state (i.e. transistors and integrated circuits a.k.a. "silicon chips").
Collins speaker, 75S-3C receiver and 32S-3 transmitter. (Source: Wikipedia)
Click here to see some more pictures of amateur radio stations. If they look intimidating, note that just one or two of these boxes is enough to operate an amateur radio station — but, like with other hobby related items, many people find it hard to stop at owning just one or two.
The Yaesu FT-990 is a quality amateur radio transceiver that's worth around $1000 secondhand.
Yaesu FT-990 HF Amateur Transceiver. (Source: Radioaficion.com)
You can search for amateur radio transceivers for sale in online auction sites and other places using the search phrases (without the quote marks) "yaesu ft", "kenwood ts", and "icom ic".
Antennas for Amateur Radio
Antennas to transmit, especially on the lower frequency HF bands, can be quite elaborate. Because the physical length of the antenna is related to the wavelength, long radio waves need long antennas to work efficiently, especially with transmitting.
On the longer wave bands, antennas are usually some sort of long wire(s) arranged in a particular way, such as a dipole, inverted vee, or end-fed antenna. The antenna that's probably written about the most in introductory radio material is the half-wave dipole, which is basically just two pieces of wire in a straight line, connected in the centre to the feedline (i.e. the wires that connect the antenna to the transmitter). The total length of the whole antenna (including both pieces of wire) is half a wavelength. So on 40 metres, a half wave dipole antenna would be 20 metres long, with each individual piece of wire 10 metres long.
While the half-wave dipole is perhaps the simplest antenna to understand the theory of, and requires the simplest design, it's not always the easiest or most practical. An easier antenna for many people is the end-fed antenna, which is only one long piece of wire connected to the transmitter at one end only. And end-fed antenna requires a balun and an antenna tuner. You can make one by following the instructions here. The balun can be built yourself (if you can solder) or purchased. If you want to buy one, try searching for both "baluns for end fed antenna" and "ununs for end fed antenna" (but without using the quotes in the search engine). These are also excellent for shortwave radio listening. The advantages of the end-fed antenna are 1. you only need to connect the long wire at one end, which gives you vastly more options for stringing it up on an ordinary house block and in many other situations, and 2. unlike a dipole antenna, the same antenna can be used on more than one band.
On the short HF bands such as 10 metres and on VHF and UHF, "Yagi" antennas are common, which look like TV antennas except they are much larger for HF and 6 metres. On VHF and UHF, amateur yagi antennas can be similar (in construction and size) to VHF and UHF TV antennas.
Mobile HF antennas exist, which use coils and other tricks to make the radio think the antenna is longer than it really is. This means you can transmit without frying your radio, though the signal isn't going to be nearly as strong as a long base-station antenna.
Standing Wave Radio, or SWR is a measure of how much of the transmitted signal is reflected from the antenna, back into the feed line between the antenna and the transmitter, and then back into the final stage of the transmitter. Ideally, SWR should be 1 to 1 (written 1:1), which means that all of the transmitter power is going out into the antenna (and then into the sky as airwaves) and none is reflected. The closer the "match" between the antenna and the radio, and the better tuned the antenna is to the frequency you're transmitting on, the lower the SWR. If the SWR is too high, a lot of power will be reflected back into the radio internals which will destroy them, and either you will have a large repair job or your radio will be completely dead. The closer to 1:1 the better, realistically anything under 1.5:1 is probably okay.
The easiest way to reduce the SWR and to match the antenna to the transmitter is to use an antenna tuner connected between the transmitter and the antenna. Using an antenna tuner is a bit like cheating in that it fools the radio into thinking your antenna is better matched than it really is. This means that your radio won't be destroyed from too much reflected power, but it also means your signal won't get out (i.e. be transmitted) as well as it would if your antenna was physically better matched.
To measure the SWR you need an SWR meter which works on the band you want, and can handle the power levels (in watts) that you plan to use. The wattage rating of an antenna tuner is the maximum power it can handle, so it's no problem having one with a higher power rating than you're using (except for the higher price of buying a higher power antenna tuner). Some transceivers and many antenna tuners have SWR meters built in, or you can buy standalone SWR meters.
SWR is more of an issue on the HF bands, because the allowed power levels are a lot higher (so there can be more reflected power to damage the radio) and perhaps for other reasons I can't think of at the moment.
Commercial Two Way Radio Systems
Morse Code is by far the most efficient method of radio, in terms of the distance that signals can be sent and heard over using limited electrical power and limited antenna technology. This means that in the future, or in an emergency, there will be a practical use for Morse Code that has not existed since the time of World War II.
As of 2015 the United States Air Force still trains ten people a year in Morse. I'm not sure how many (if any) are trained in Australia. Morse Code is often referred to as "CW" by amateur radio operators. This stands for "carrier wave" which is the type of electrical signal used by the radio to send and receive Morse Code.
How to Learn Morse Code
If you want to learn morse code, the way to do it is to start with listening (receiving) rather than trying to practice sending. You write down the letters as you hear them using paper and a pen or pencil. You don't need any other equipment (such as a Morse Code key) to do this. Look on YouTube for morse code lesson. Such as here.
Once you can receive at about 5 words per minute (wpm), in Australia you can try listening to the practice broadcasts by the Wireless Institute of Australia (WIA) at 3.699 megahertz. I think there are some other frequencies can hear it, which I'll look up later on. To hear these you need a shortwave radio that can pick up SSB signals. The practice broadcasts run 24 hours a day and cover a range of speeds: 5 wpm, then 8, 10, 12, 15, 20 and 25 wpm for about 5-6 minutes of each speed, and then starting over again at 5 wpm. In between each there's a short identifying message sent at (I think) 10 wpm. If you tune into it and it sounds insanely fast, wait until it gets back to the slow 5 wpm and then see if you can receive it (by writing the letters down on a piece of paper as you hear them).
The slower three speeds of the WIA practice broadcasts use what's called Farnsworth timing (or Farnsworth speed) which means the individual dots and dashes in each letter are sent at a faster rhythm, and then longer spaces between letters are used to give a slower overall rate of words per minute. In the WIA broadcasts the three slowest speeds are described as being 5/12, 8/12, and 10/12 wpm. 5/12 means the overall speed of the message is 5 words per minute, but the spacing of tones in each letter is faster at 12 wpm, which makes the letter sounds easier for our ears to recognise.
Once you can receive Morse Code, sending is quite easy. Since you already know all the letters, all there remains to do is to focus on getting the rhythm correct — that is, getting the right length of the spaces between letters and between words. To practice sending you could tap on a desk, or perhaps use an app or your computer mouse, however it would be better to buy an actual morse code key and connect it to a buzzer of some sort, usually termed something like a "Morse Code practice oscillator".
Outback HF Radio
These use a set of fixed frequencies and no not require licensing exams or detailed technical knowledge like amateur radio does.
See here (mainly), and also here or here for now.
Mobile phones / cell phones don't work without a functioning base tower to communicate with, so they will be of no use without grid electrical power supplied to the towers. Without a tower to connect to, two perfectly functioning mobile phones are completely unable to communicate with each other apart from ultra short range protocols like bluetooth (range of about 10 metres) or Wi-Fi (range of about 100 metres). There have been some experiments to extend this to several hundred metres or more which may be useful in the future in certain situations.
While there is still grid power mobile phones are of great use in bushwalking and camping trips.
Radio Distress Beacons
See here on Wikipedia for more.
Personal Locator Beacons (PLBs) are lightweight and can be used for bushwalking. See here for more.
Emergency position-indicating radiobeacon station. These are larger and often used for boating.
Emergency Locator Transmitters are usually used for aircraft.
Underwater (Submarine) Radio
Electromagnetic Pulse (EMP) Attacks
An Electromagnetic Pulse (EMP for short) is a short lived pulse which can instantly and permanently destroy most electronic devices that contain semiconductors (e.g. microchips), including computers and communication devices. EMP will be the subject of an entire page which is coming soon.
NEW: Entire page on EMP.
A single nuclear bomb detonated high up in the sky (like 400-500km) would generate an EMP over a wide enough range to affect the whole of Australia, or the USA. In contract to a nuclear weapon detonated close to the ground, an explosion at that high an altitude will not produce physical damage on the ground like a usual nuclear attack, other than any physical damage that the EMP itself creates, like power lines heating up and setting things on fire.
The effect of an EMP like this would be to instantly put an end to our entire modern way of life. This is because of the huge dependency our modern lives have on computers and other EMP-sensitive devices. This would include the entire banking system, including all records of bank accounts, so that money (apart from cash in notes and coins) as we know it would no longer exist. Also the electrical power grid would be destroyed, not only because of the computers that run it but the long wires themselves are a massive antenna for EMP. Without computers and electrical power the water supply would also be gone. Cars are somewhat shielded against EMP already, because the body of the car is metal, and the engine bay, and the semiconductor circuits in cars are often encased in metal boxes on most or all sides. Due to this, the effects of EMP on cars is largely unknown and conflicting views may be found from searching the internet. All cars made after roughly 1980 have some amount of EMP-sensitive circuitry in them, however the degree of shielding the car's own metal construction provides is not well known.
A study done by the USA government is often quoted as evidence that cars (even modern ones) are not easily damaged by EMP. However in that study the cars were exposed to gradually increasing strengths of EMP fields, until any effect at all was noticed (like the blinkers turning themselves on), after which that car was not tested any more (i.e. using higher strength fields). Then that data was used to conclude that cars are not permanently damaged by EMP, which is obviously going to be true if the cars are not subject to strong enough levels of pulse.
Clearly it's impossible to actually test such a long-range EMP weapon, and because of this there are a lot of unknowns.
Protection Against EMP
The way to protect an electronic device against EMP is to have it shielded, which means to have it completely surrounded on all sides by a continuous layer of electrically conductive material such as metal. If there are gaps in the shield, it will reduce the level of protection. It's also important that the shield doesn't touch any part of the device being protected that's electrically connected to the device itself (like the antenna of a radio).
Perhaps the quickest practical way to shield a small electronic device (such as a radio) would be to put it in a plastic bag and then completely wrap the whole thing in aluminium foil, so that the foil goes all the way around on all sides with no gaps. It's suggested that 3-5 separate layers of aluminium foil will probably give good protection.
Another easy method is to buy a metal garbage can and put items in there, making sure the metal lid touches the metal can and nothing in the can is holding the lid up and stopping the electrical contact. The garbage can (and other metal boxes) can be further improved by wrapping conductive tape (such as copper shielding tape) all the way around the lid-can join, completely sealing the can to the lid electrically.
Higher levels of shielding can be obtained by using more than one shield, one inside the other (such as aluminium wrapped and inside a metal garbage can).
NEW: Entire page about EMP.
Another really good page about EMP protection (external link)
Tasks to Complete HOT
This is in order of priority, based on importance/usefulness and how easy and cheap they are to do. More pictures to be added soon.
Economic Instability List
If you follow this list step by step, you will end up with several different radios. This is intentional. Radio equipment increases in price exponentially, meaning you can have ten $10 radios for the price of one $100 radio. You can have ten $100 radios for the price of one $1000 radio. Starting from the cheap end of the list you can achieve a lot with little money or effort — and keeping these cheap radios while adding more expensive gear is a hugely more failsafe setup than having only one item of expensive radio gear.
- Buy at least one (ideally more than one) small, portable radio(s) that can receive at least the commercial AM and FM bands. The power source must be completely independent of mains electricity, such as batteries or solar panels or a wind-up crank. Keep the radio in a plastic bag which is covered completely on all sides by aluminium foil, and/or some other means of EMP shielding. The AM band in the evening and early part of the night is best for long-distance reception. These radios start from prices that are quite cheap (like $10-20 or even less) and can hear commercial broadcast stations up to hundreds of kilometres away.
- Add another radio receiver, ideally it should be kept in a different location (e.g. your car or office), and also EMP shielded. Everything in this list should be EMP shielded when not in use.
- Increase the range by adding a basic wire antenna (at least a few metres long) to pick up weaker and more distant radio stations. If the radio has an external antenna, this can sometimes be clipped onto it. Note that many cheap radios with AM and FM only use the metal telescopic type antenna for FM and have an internal "ferrite rod" coil antenna for AM, where the antenna is a coil of wire wrapped around a black rod made out of material called ferrite. In this case it may be difficult to connect an external AM antenna, and you want AM for long range reception rather than FM. Look for radios that allow an external AM antenna to be connected.
- Get a radio receiver that can pick up: the shortwave band. This will give a listening range of thousands of kilometres, and even worldwide reception with a good enough antenna.
- Get a sideband (a.k.a. single side band, or SSB) capable shortwave receiver.
More coming later.....
Bush/Wilderness Trip List
- Have some means of contacting others by radio. For most people this would be a mobile phone. Be aware of how to conserver battery power, including putting the phone in low-power mode, turning down the LCD brightness to minimum, turning off unnecessary things like Wi-Fi and Mobile Data, and using text messages rather than voice to both conserve battery power and increase range of reception.
More coming later.....
Preparing for an EMP (Electromagnetic Pulse)
Survival and Wilderness Skills Books
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