Bunch of lazy sods
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
Thoughts on Survival Radio
by LightSpeed - 6th January 2012
http://survivaluk.net/2012/01/06/thought...val-radio/
Two-way radio should not be overlooked by preppers, this article is written to assist preppers in making radio equipment
choices, and it is written on the premise of a post major event scenario in which all mains power utilities are permanently
down.
Without mains power it is likely that there will also be no television, no telephone, no mobile phone, no internet, no radio
repeaters etc. Radio will be the critical communications tool for monitoring the outside environment, communication with
other survivors, and maybe for summoning help.
The author’s personal plan is to assemble a station that will allow discreet communication, locally, nationally and globally.
The installation is required to be VERY covert so as to draw absolutely no attention to the station either pre or post event. The
station is planned to be operational over a long time period (say 10 years), to be powered by simple power generation methods,
and where possible be user serviceable using low(ish) tech solutions.
The manner of description of various issues has been very much simplified to aid comprehension of non specialist readers.
This is particularly true in the section on Propagation and antennas. For anyone particularly interested in this subject there are
many published articles that can be followed up.
1. Power supply considerations
Other than cats whisker crystal radios, all of the devices discussed in this article need electrical power. The most readily
available power to survivors is likely to be 12v and solar rechargeable 1.2v dry cells. Additionally 12v to 5.2v USB car
adaptors are now readily available at low cost. Recharging of these power supplies can be through mechanical generation of
12v and 5.2v by dynamo / alternators, or by solar cells. (for example, I have successfully run long term tests of solar
recharging of AA cells using a bank of solar garden light heads. The recharged batteries have kept a very modest radio station
running 24/7 for a whole year)
2. Basic specification of survival radios:
2.1 Low power consumption
Power will be a precious resource, which we will need to use carefully. Because of the power supply issues discussed above
we should be looking for radios that have just enough power to make communication possible.
OK, so how shall we define low power? Well, radios with power output of 0.5w (watts) to 10w are completely capable of
delivering reliable local and as well as global communications. (Radio amateurs refer to this as QRP power). It is logical to
assume that low transmit power radios draw proportionately less power than high power transmitters. This is largely true, but
not always so. (see section 8 Equipment Review)
Post-event, the number of privately held radio stations operating at high power will be extremely limited. This will have the
effect of making low power radio stations even more effective as radio generated interference levels will also drop, allowing
weak signals to be heard over greater distances.
Another aspect of using an appropriately small level of power is that it is more discreet, so attracting less unwanted attention
from folk who may not have your best interests in mind when they hear your transmissions.
2.2 Robust
The operating conditions for survivalist radio equipment can be expected to be poor. Only robust equipment, or equipment
who’s durability can be improved is likely to remain in service for long. As radios are sensitive (literally) electronic devices
1 / 7
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
their biggest susceptibility is to getting wet. We need to purchase waterproof gear, or more economically, find ways to keep
our gear in water-proof containers.
Again, power supply is going to be critical to long term viability of your equipment: The latest Lithium cell powered devices
are going to be fine for a number of years operations (provided you can charge the batteries which are usually 7.2v) Best is to
find devices that can be alternatively powered directly by a 12v supply, or by dry cells (AA, AAA etc)
2.3 Repairability
If long term usage is planned, it is a good idea to select equipment that is both repairable and within your competence to repair.
Repairs to commercially manufactured equipment will be outside of the capability of most people. Transceivers with ultimate
repairability are likely to be Amateur radio kits. However, a word of caution, by their very nature, such radios are inherently
less reliable than most commercial units so require more running repairs.
2.4 Appropriate frequency ranges
It is important that the radios we acquire operate at frequencies that are either:-
in wide usage (to contact other survivors)
Broadcast FM receive bands for local Government Broadcasting
Broadcast AM receive bands for National Government Broadcasting
Broadcast LW receive bands for national and European Gov Broadcasting
Shortwave AM receive bands for worldwide Governmental Broadcasting
Shortwave Amateur Radio Bands
VHF / UHF FM Local Amateur Radio
High Frequency (HF) SSB and CW ( Single Side Band and Morse Code) Global amateur radio
or in restricted usage (for more covert group communications)
2.5 Availability:
We need to consider which users and equipment is most active and readily available pre-event as these will probably most
prevalent after event as well. Standard radio receivers to pick up commercial and national broadcast stations: FM, MW
(Medium Wave), LW (Long Wave) and SW (Short Wave) Available everywhere at very low prices. For local communications
PMR446 family hand held walkie-talkie radios are the most prevalent radio transmitters in the UK today. Think about it:
Probably most families with children will have several these radios in one form or another. All of these radios are simple to
operate, somewhat child-proof and therefore robust, and they also conform to a very tight standard in terms of channel
frequencies. They are not very repairable, but can be readily replaced.
Amateur Radio: Generally good quality and reliability, but complexity can be difficult to master without prior operating
experience. Amateur radios can be a good choice, but remember most will be locked to frequencies allocated to amateur use. It
is legal to own this type of radio, and indeed to use it as a receiver, but to transmit a license is required. (see Getting and
Amateur radio License) Be warned that at the current time the amateur radio frequencies are policed and pirate stations are still
tracked down and prosecuted in law.
CB Radio: Rather gone out of fashion in the UK, but radios are still available on e-bay at very low prices. Probably good only
for pre-organised group local communications. Post event it is assumed that some dormant radios will be come back onto air,
but there is no way of assessing what numbers are likely to be.
Marine VHF radios: Again, legal to own, but transmission not legal without a license. Restricted to marine band, which
includes Coastguard, air-sea-rescue and Mountain search and rescue. Often bullet proof waterproof construction. If you live
near to the sea, or better still a marina or even navigable rivers, there may be useful numbers of transceivers in place.
3. Understanding Propagation
Propagation is the technical term to describe how radio signals are radiated over various distances. Propagation is of great
2 / 7
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
interest to us as it tells us what is possible, what is not possible with various pieces of equipment at various times.
3.1 A little science needs to be understood to make sense of propagation:
Radio waves are the lowest frequency section of the electro-magnetic radiation spectrum that includes infra-red, visible light,
ultra-violet and x-Rays. Like visible light, radio waves generally travel in straight lines, and identically to light they travel at
approximately 300,000km per second (186,000 miles per second in old money) in vacuum. From a point source (an antenna)
radio waves will radiate in hemispherical pattern, much like half of a soap bubble. Using the same analogy, the bigger the
bubble gets the weaker the signal that will be heard, a bit like the thickness of the wall of the bubble getting thinner and thinner
as it expands. Like light radio waves will travel to infinity in a straight line. For example NASA’s communications with the
voyager space probe used just a few watts of power to communicate half way across our solar system.
The concept of radio waves travelling is a straight line is important. Another way to look at it is that radio waves will only ever
travel as far as Line-Of-Sight unless reflected, refracted or re-transmitted. Over the sea, line of sight is approximately 20 Km
/12 miles. (see KD4SAI's VHF/UHF Line of Sight Calculator) But this is far less than the distance we know radio waves can
travel, how can radio waves overcome the “line of sight” statement made earlier? Well the most simple way is the elevate the
antenna: The higher it is the greater its line of sight. This is why mobile phone masts are located on hill tops, church towers
and tall masts. At certain radio frequencies / wavelengths, radio waves are reflected and refracted by the upper layers of our
atmosphere that get ionized by sunlight. These layers are like the layers of skin on an onion and are called the ionosphere.
They exist at altitudes of between 85 and 250 Km. Radio waves hitting the layers of the ionosphere at critical angles and at
critical radio frequencies / wavelengths, are reflected / refracted off and between the various ionized layers. In effect the
ionosphere is a giant spherical mirror 100s of km above the earth that reflects certain radio frequencies (but not all) back to
earth a great deal further than terrestrial line of sight.
The word critical has been used several times here. When light is separated by a prism into spectral colours the angle at which
the incident light beam make with the glass prism is critical in determining if the light gets transmitted straight through the
glass, reflected off its surface, or refracted within the prism. So it is with radio waves, other than at the critical angle the radio
wave will pass straight through the ionosphere and out into space. Things are made more complicated as different radio
frequencies have different critical angles, and the various reflective layers change in altitude and intensity throughout the solar
day/night cycle. What is more some radio frequencies are not reflected by the Ionosphere at all. Frequencies in the VHF and
UHF region are never reflected. This means that they are only suitable for line of sight communications. If you live on a
mountain top this may mean 100Km or so, but generally it should be expected to get no more than 20km in ideal conditions.
Ideal conditions get compromised by foliage buildings and other physical obstructions between transmitter and receiver.
3.2 Time of Day
At the lower High Frequency end of the Short Wave band, the frequencies of approx 2MHz to 30Mhz will all be reflected and
refracted by the Ionosphere to a greater or lesser extent. Because of the variable critical angles and frequencies we can
generally view Ionospheric propagation divided into usable daytime and night time frequencies. Broadly speaking, frequencies
greater than 7Mhz will achieve longest propagation distances during daylight hours and frequencies below 7MHz will achieve
longest propagation distances at night. The converse is also true after nightfall frequencies above 7MHz become progressively
more line of sight, and after daybreak frequencies below 7MHz become progressively more line of sight (and the lower
frequencies are affected by high levels of noise as well)
Ionospheric propagation frequently supports multiple reflection within the ionosphere without too much signal absorption.
Under the right conditions trans global communications are possible at very low power. Communications between UK and
Australia using 0.5W is possible. Here is an actual communication between USA and Indonesia using just 5w. These
phenomena are possible only because of Ionospheric reflection.
3.3 Yearly and 11 year Cycle
The degree to which ionization takes place to the various layers of the ionosphere varies month to month and also within an 11
an (approx) 11 year cycle of solar sun-spot activity. Simply put, the higher the level of ionization the greater the efficiency of
the Ionospheric reflector. This is particularly true at the 27/28/29MHz end of the spectrum which is almost worthless for long
distance communication during low points in the 11 year cycle, but which becomes arguably the best long distance frequency
3 / 7
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
at the high points of that cycle.
3.4 Dawn and Dusk
Dawn and dusk see some abnormal behavior of the Ionospheric reflector and sometimes offer conditions of enhanced long
distance propagation. Monitoring at this time of day will often yield radio signals from unusual parts of the globe.
3.5 Skip Zone and NVIS
We know that radio signals travel by line of sight (say 20Km) unless reflected or refracted. So when a signal is successfully
reflected from the ionosphere to a station say 1,500km away, what happens in the space between 20km and 1500Km? The
answer is that nothing is heard in this zone. The radio signal beam is overhead at this time and cannot be detected at ground
level. This is called the skip zone or Dead zone. This creates a dilemma, how do we communicate with stations within the skip
zone, i.e. nationally, not internationally. Well the solution is to use an antenna technique developed for tactical military
purposes. It is called NVIS (Near Vertical Incident Skywave). NVIS offers propagation to stations between the limit of line of
sight and up to approx 1000Km.It is covered in the antenna section of this article (below)
3.6 Amateur Radio Repeaters
The purpose of Amateur repeaters is to extend the range of VHF and UHF communications by receiving signals on one
frequency and re-transmitting them on another. Repeater masts located at the edge of a stations line of sight, and ideally in an
elevated position will greatly extend the transmission range of the otherwise local only capability of this equipment. Indeed
some repeaters are internet enabled and permit trans-global communications using simple hand held transmitters. In this article
it is assumed that Amateur radio repeaters will be out of commission due to mains grid power failure, so will not be discussed
further here. Again, for anyone wishing to find out more information on this aspect of Radio technology, much information is
in the public domain on the www.
3.7 Propagation Conclusion (Applicable to transmission and reception)
Use frequencies below 7MHz for long range (DX) operating during hours of darkness.
Use frequencies above 7MHz for long range (DX) operating during daylight.
Use VHF and UHF frequencies for local communications day or night up to say 20Km.
For communications between 20Km and 1000Km NVIS antenna Techniques should be employed.
4. First seek to understand, then to be understood.
Recommendation is to firstly equip ourselves with a radio receives, so that we can listen for signs of activity in the surviving
world. Listening to other people’s radio communications will give us good intelligence on what is going on around us without
the need to leave our safe havens. It is very good practice to listen for an extended period in order to assess what is happening
in the outside world. Gradually patterns of operating behavior will emerge that we will be able to predict. We must not be
tempted into communication just for the sake of it. Listen first to see if predators are taking advantage of unwary stations in
order to raid their locations. Our primary advantage will be our pre-preparedness, we should not squander it by giving away
your location either directly or indirectly.
We should consider being able to monitor the following:
Broadcast bands: FM / AM / LW / SW
PMR446
Emergency services / Airband / Military (military comms will be scrambled)
Amateur Radio VHF / UHF (Local) and HF for world-wide transmissions
5. Transmitters and transceivers
5.1 Transmission Modes and efficiency
The method of encoding information into the transmitted signal is called the transmission Mode. The different modes available
4 / 7
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
each have advantages and disadvantages from a quality: efficiency standpoint. By quality we mean the easiest to hear and
understand, by efficiency we mean the greatest distance per Watt of transmitted power that the message remains intelligible.
FM Frequency Modulation: Highest quality but lowest efficiency. Excellent for VHF and UHF line of sight
communications. Also used on UK legal CB frequencies to good effect. Very resistant to interference, and good
intelligibility.
AM Amplitude Modulation: Similar characteristics to FM, but more prone to interference. Very inefficient
power-wise. Largely unused these days by Amateurs, but still a major Broadcast format of course. Some illegal
US import and vintage CB radios are still operative in UK on AM.
SSB Single Side Band: The most efficient voice transmission mode. Comes in two flavours Upper Side Band (USB)
and Lower Side Band (LSB). Requires careful tuning of the receiver to render speech intelligible. Almost all long
range voice communications are made in SSB mode.
Note: accepted operating convention is that for frequencies above 10MHz USB is used, below 10MHz LSB is
used.
CW Continuous Wave ( Morse Code) Do not discount Morse code as outdated. It is by a very long way the most
efficient transmission and reception mode available to us. 1/2watt power output (same as PMR446) but on HF
bands regularly achieves trans global contacts on CW. In a survival communications scenario we will have time to
study and learn the Morse code. Transmission can be very slow and repetitive to get messages across.
Tip: Morse code and to a lesser extent SSB can be resolved even on low cost AM receivers. Often the Morse code
pulses can be heard as nulls in the background noise. Try placing a second receiver very close to and tuning it to a
our active receiver and tuning it to a similar frequency. Often interference from the second receiver can be used to
make the CW tone appear, likewise SSB can become more intelligible. A low cost BFO ( Beat Frequency
Oscillator) kit is available from Ten Tec to perform this upgrade function more reliably.
Digital
Modes
A highly efficient digital mode called PSK 31 has been developed by amateurs. It involves the use of computers to
generate automatic tone based keying of the transmitter. While very efficient transmission wise the fact that it
requires a computer to drive it and interpret incoming signals disqualifies it as a low energy consumption
communications method in this article.
5.2 Types of Transceiver;
5.2.1 PMR446
Not all PMR Radios are the same. USA import PMRs with extended range are being offered on e-bay at this time. They are
illegal to use in the UK and are not compatible with the European PMR446 standard so cannot inter communicate with them.
From a survivalist standpoint PMR446 is of interest primarily because of its high prevalence in the community. US PMR
radios are only of interest if you plan semi-private group networks, but better solutions are available using the low cost Chinese
hand helds described below and in section 8.
The ones we are interested in are of the PMR446 standard. These are all FM mode with 0.5w power output on 8 standard
frequency channels through a built in, non removable antenna. Expect transmit range to be 1Km or less and you won’t be
disappointed. In the open or in a good elevated location these radios will easily achieve the claimed 5Km range but such
conditions are not the norm.
Ignore claims of hundreds of Channels this refers to so-called privacy codes (see below)
Features to look for are CTCSS and DCS tones and scanning, plug in headset sockets and the ability to operate with security
codes off. (some early generation Motorolla radios do not have a no code facility)
Variable Squelch control is an asset. Squelch is a user tuneable noise threshold over which the receiver operates. It is designed
so that your do not have to listen for signals within static as this is fatiguing, when a signal stronger than the background static
is received, the receiver is opened up and the signal heard, otherwise the radio will be silent.
Radios that are sold with only AA or AAA dry cell / rechargeable cell capability are a better long term survivalist tool than
those sold with bespoke power packs. Check to ensure that there will also run OK on rechargables and standard dry cells
(different voltage therefore different amps to deliver the same output power.)
Radios with cases that can be unscrewed and dismantled are preferred, as, if you intend fitting an external antenna to improve
reception you’ll need to get into that case somehow. But note that this will technically render the radio illegal under today’s
legislation.
5.2.2 Hand Held Amateur VHF and UHF radios
1.0w to 5.0w capability FM radios with CTCSS and DCS capability
Range 3 to 10Km in normal condition, and up to full line of sight from open / elevated locations.
5 / 7
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
100+ memory channels, usually nameable and in fast retrieve blocks make operation fast and simple.
Some new low cost variants are now available out of Asia that off wide band transmit and receive capability such that single
devices can now interact with Amateur VHF and UHF bands, Military Bands, PMR446 and Marine Band.
Marine band distress frequency as used by Coastguard, air sea rescue, mountain search and rescue.
5.2.2.1 Privacy codes and CTCSS / DCS tones
CTCSS and DCS tones appear on PMR446, CB and Amateur radios. They are all too often described a Privacy or secrecy
tones, when in reality they are no such thing. These tones are discreet audio and Digital tones generated in the transmitter with
are transmitted along with your voice signal. No encryption or secrecy coding is applied to the spoken message which can be
listened to by any receiver tuned to the correct channel frequency.
The purpose of the tone is to allow suitably equipped receivers to ONLY HEAR signals on the same frequency to which they
are tuned and also carrying the same discreetly injected tone (ie both transmitter and receiver must be set to the same
frequency/channel AND also set to the same CTCSS or DCS tone, otherwise nothing will be heard). The intention of the
technology is to enable concurrent multiple users of the same channel on PMR446 devices. It is only partially successful in this
respect.
NOTE: During the Olympics there should be a lot of PMR446 activity in London with friends and families using them as a low
cot way of keeping in touch. It will be interesting to monitor activity to see how well CTCSS and DCS systems work, also to
hear what the system sound like in conditions of possible overload.
Some older PMR radios ( Mororolla for example) can only operate with CTCSS tones activated, the description of PMR446
requirements above notes that tone scanning is desirable as persons using such equipment will not be able to hear signals from
you unless they carry the same discreet codes. Amateur radio has made most use of CTCSS coded as access codes to VHF and
UHF repeaters (see Propagation section)
Monitoring with codes OFF allows you to hear everything in your vicinity.
5.2.3 Amateur HF radio equipment
Amateur HF radio equipment comes in all sorts of shapes and sizes. In the low power, portable category evaluated in this
article the breadth of choice is somewhat reduced. There are both commercially constructed and kit type radios in this
category.
Additionally there is ex British military equipment available. The author recognizes that this equipment may be ideal for
survival communications, but has no experience of operating such equipment. Maybe someone with specialist knowledge can
offer advice or write a specific article on this?
Primary separator between commercial machines and kits is transmission modes. Kits tend to be Morse code only, whereas
commercial radios are voice and Morse code capable.
Commercial Manufacturers
Primary manufacturers are Yaesu, Icom, Kenwood and Alinco.
A lot of commercial transceivers are rated at 100w power output but gave variable power control, down to 5w. Read
specifications carefully before rejecting a radio as too powerful. In the review at the end of this article I have only included
radios capable of running at low power even if they are also capable of higher power output. Yaesu and Icom offer small form
radios (car radio size) that potentially fit all survival radio requirements into a single box. They are broadband receivers that
can tune the whole shortwave HF band, Air Band, Marine Band, VHF and UHF. They have sophisticated noise reduction
systems that aid reception of weak signals and are capable of transmitting in AM/FM/SSB/ CW and digital modes. Among
these, Yaesu’s FT817 is most recommended. Others from Yaesu are the FT857 and FT897 and from Icom the IC 706 and IC
7000.
Modern manufacturing processes are largely robotic, and components now used in construction of consumer electronics are
super small. Modern machines are very reliable, but fixing them when something goes wrong is a complex affair.
Commercial transceivers are in four formats:
Hand Held Self contained “walkie-talkies” for the VHF /UHF bands
Portable Self contained HF radio stations. Currently there are only three models in production. Yaesu’s FT817
(highly recommended) and the Albrecht AE 2990 10 meter hand-portable. Both offer Am /FM /SSB and
CW modes. And a soon to be launched Elecraft KX3 which promises to be an excellent product for HF
6 / 7
Thoughts on Survival Radio - 6th January 2012
by LightSpeed - Survival UK -
http://survivaluk.net
operating.
The Yaesu and Albrect both operate from rechargeable internal batteries as well as 12v external supplies.
Mobiles Small form factor radios for use in motor vehicles these are all 12v supplied, and available for both HF and
VHF/UHF.
Desk top Large form factor radios designed to be used in fixed radio stations.
5.2.4 Kit Radios
HF radio kits are the prime interest here. VHF and UHF kits exist but they tend to cost very much more and have less features
than their commercially manufactured equivalents.
Compared to commercial radios kits are far simpler and less refined, but are still capable of intercontinental communications.
HF kit radios are a fraction of the cost of commercial equipment, and have two big advantages in survivalist term:
They are extremely power efficient, and often will run happily on voltages from 7v to 15v.
They are user repairable long into the future provided you also have spare parts in your provisions.
Many of these kits are quite simple to construct. If you have built Airfix model in the past, the construction of many of these
radios will be within your capability. Basic equipment you’ll need is solder, soldering iron, clippers, magnifying glass, and a
test meter.
Although primarily Morse code only devices, there are a couple of SSB capable kits available too. Critically these are designed
for the primary 7Mhz and 14Mhz frequency bands (see 6.7 below)
These radios can be constructed into very small containers, making them easy to store in waterproof boxes and thus strong
contenders for inclusion in bug out provisions.
Consider this: With home brewed minimal solar cell battery power it has been possible to keep a receiving/transmitting station
on line 24/7 for an entire 12 month period in southern England. There was no equipment failure whatsoever during the trial and
it was considered probable that this setup could remain in service for several years. Communications across mainland Europe
and also to a number of USA states were achieved during the trial period. Cost of the entire station was under £50.00.
Kit Radios in this category come in two power bands:
1/2Watt and belowLowest cost, Morse only. Require LOTS of time and Patience to achieve contacts. But they do work.
2w and above
Powered by TCPDF (
http://www.tcpdf.org)
7 / 7
Search
Calendar
Help
