Radio Communication (for emergencies)

Note that this contents is an unapproved draft and DOES NOT REPRESENT THE SETTLED VIEW OF CAMBRIDGESHIRE RAYNET. It may be wrong, incomplete or deleted on review.

Why Radio?

This discussion is an introduction to the use of radio systems for situations when more normal forms of communication such as telephones and internet are, or have become, become unavailable. Technical detail is kept to a minimum unless it's necessary to understand the issues. There's a presumption that the situation is an emergency rather than conditions-as-normal and the reader is determined to understand how radio systems might help. To do this, a small amount of both technical and legislative background is unavoidable.

What Is Radio?

Most people are familiar with using radio communications, either using broadcast radio at home or in vehicles, using cell (mobile) phones for voice and data or WiFi for internet access. These all make use of the fact that information can be sent through space from one point to another without needing wires - indeed, before the popular name of 'radio' came into use, this used to be known as 'wireless telegraphy'. Wikipedia has much more detail[1] if you wish to read it.

Radio-based systems are extremely common in modern life because of this ability to send and receive messages without needing a connection. Radio is exactly the same phenomenon as light - they are both a form of vibration in the electromagnetic properties of space.

The only difference between what's normally called radio and visible light is how rapidly the vibrations happen: their frequency, which we measure in Herz (Hz) - 1Hz is one vibration per second. Visible light vibrates somewhere around 500 million million times per second (500 TeraHertz or 500 THz) whereas most practical radio systems make use of frequencies ranging from a few million Hz (megahertz/MHz) to low numbers of GHz (giga hertz, thousands of megahertz). The frequency has a profound effect on how radio works at a terrestrial level, it's deeply relevant.

It's common to refer to 'radio waves' or 'signal' when talking about this phenomenon. Cellphone users will be familiar with 'I have a bad signal here' when almost out of range of the base station that is relaying your conversation.

Radio signals travel very quickly. Unsurprisingly, since they are essentially the same thing as light, they travel at the speed of light[2], very close to 300 million metres per second, 700 million miles per hour. For practical purposes, unless you are communicating via spacecraft, radio communications on Earth are instantaneous to human perception. People familiar with the Moon landings in the 60s and 70s will however remember that Earth-Moon-Earth communications experienced a delay of about two seconds for the round trip.

As examples: broadcast FM radio uses around 100 MHz, Air Traffic Control about 120 MHz, WiFi typically either 2.4 GHz or 5 GHz. Satellite TV in Europe is beamed down from space mostly in the range 10-12 GHz.

The frequency affects how the radio signals travel. Bodies of water are remarkably opaque to most frequencies with the curious exception of visible light - almost certainly the reason that eyes developed to detect signals in that frequency range. Conversely, the lower frequencies commonly used for radio communications can partly travel through modest obstructions like brick walls. Frequencies in the 0.1-3 MHz range have a strange property of 'hugging the earth' so they can go over the horizon and, remarkably, in the 1-30Mhz range, the sky can act like a mirror, reflecting radio signals back to earth instead of letting them pass and this is hugely useful for sending messages around the world - reflecting them off the sky. Predicting the reflective properties of the sky is a very specialised skill as it depends on the effects of sunlight on gases in the atmosphere. Online tools like VOACAP[3] are very useful for this task.

Radio specialists have a huge range of frequencies to choose from depending on what they need to achieve - there is no 'best', just an engineering choice of trade-offs between range, power and reliability requirements.

Because radio signals can travel long distances and because some are used for critical communications like Air Traffic Control and other safety-of-life purposes, the use of radio frequencies is strictly controlled by legislation at both national and international level via forms of licensing to ensure safety, reliability and lack of interference. Most frequencies are reserved for various uses including broadcast, commercial, research, military and similar purposes. Cell/mobile phones appear licence-free but they are actually using the telephone company's licensing. By international agreement some limited frequencies are available to be licensed for non-commercial/research/leisure purposes to individuals classed as 'Radio Amateurs', others are licensed in such a way that they can be considered 'licence free': these include

  • CB (Citizens' Band) Radio
  • Leisure Radio such as PMR446 across much of Europe, FRS in the USA etc.
  • Very short range devices like remote garage door openers
  • WiFi data links
  • other random carve-outs like personal locator beacons (PLBs) for those who fall off boats or get lost in wilderness

With the notable exception of CB radio which operates at around 27MHz, licence-free radios available to the general public are low-power low-range devices incapable of causing physical harm or interference to legitimate users far away. Even CB equipment is theoretically limited to relatively low power (a rule widely broken), but the power permitted is capable of covering useful distances - say 10-20 km or up to 15 miles or so under normal conditions. The choice of 27MHz is historic - when allocated, this was a frequency of little use to commercial users as it's too high for sky reflection most of the time and too low for small, efficient high-gain antennas[4]. This changes at peaks of the solar cycle[5] when, say, a UK CB user having a chat with someone a few miles away suddenly hears a very strong signal from a Russian taxi-driver in Moscow. The same effect is present on the 28-30MHz band allocated to Radio Amateurs where modest equipment no more powerful than a bright flashlamp may be able to reach Australia from the UK with ease (and luck).

Radios for Emergency / Resilience Use

Please note: the information below is UK-specific unless otherwise stated. Much will be valid for other jurisdictions but to save repeatedly having to remark 'in the UK ...' that should be taken as implied. It also explains the last c in licence, and not in licensing.

Anyone planning for resilience or emergencies where normal telephones or internet are dead is likely to want to be able to communicate with

  • their own group of helpers / volunteers
  • outside the affected area for help from police, rescue, ambulance
  • outside their area to coordinate supplies, logistics and welfare messages

This requirement is endemic if you read articles or online forums discussing these matters. There are, unfortunately few good answers for the average unprepared citizen, partly due to the regulation through licensing that's discussed above.

There are some 'obvious' solutions which tend to occur to those struggling for a solution, amongst them being

  • Satellite internet such as Starlink[6]
  • Satellite phones of various kinds
  • CB or other licence-free radio - readily available equipment, modest cost
  • Amateur Radio - needs the relevant licence, but cost-effective equipment readily available
  • Officially licensed radio systems

Each has different strengths, there is no 'ideal' fit. But: first and foremost, anything that is obtained 'just in case' tends to be used once then put away and forgotten about. When the emergency hits there is a real risk that

  • Nobody remembers how to use it
  • It has stopped working
  • There is no plan or agreement to use it effectively
  • There is a lack of skill in deploying it

For evidence of this the article Living Without Electricity[7] is a sobering read. It describes how satellite phones suffered from those issues when needed after a major storm caused city-wide power failure. Let's look at each

Satellite Internet and Voice

This is an excellent idea. Starlink[6] (other competitors are emerging) works extremely well and has proved its worth in trying conditions such a the battlefield in Ukraine. It's small, effective and providing you can justify the subscription fees and are prepared to test it regularly is very likely to be useful. Via a flat antenna resembling a dining tray, broadband internet/data can be accessed.

It's popular with caravanners, campers, sailors, film crews, relief workers and adventurers who have to travel where there is no guaranteed infrastructure for internet. It's also found as a primary source of broadband in areas where fibre is not available. The data speeds typically achieved allow for the use of voice and video conferencing applications or voice calls over suitable software including landline phones if they are digital.[*1]

Along with data connectivity, satellite providers like Starlink are also developing direct-to-phone connectivity so that ordinary cellphone devices can connect directly via satellite - a development to watch as it not currently available in the UK (early 2026). Where this service is available it seems likely to supplant the older style of satellite phone mentioned below.

A location using satellite communications will need enough electric power for the equipment being used so it's most likely to be found where there is already a backup plan for electricity provision.

The only note of caution is to ask what will happen in the case of, say, a national power outage. Low-earth satellites need to relay messages to ground stations relatively close-by and if the power outage is widespread there is a question not only of the ground stations having reliable power but, even if they do, do they still have internet access to what you need? In all probability they will be a great help, but perhaps they should not be the only egg in your basket. Prudence suggests belt-and-braces.

Satellite Phones

These are potentially useful but you should read the 'Living Without Electricity' report. Traditional satellite phones need to be kept charged-up or their batteries may fail, they typically have high monthly rental charges, you have to know how to use them and you need to be sure the people you want to call will be accessible by phone (not guaranteed in widespread power failure situations). Do your homework. They seem appealing but the appeal fades the more you learn: occasional emergency use is not a strong point in most cases.

CB And Other Licence Free Radio

These have the attraction of requiring no licence and having little or no running costs. There are numerous suppliers, plenty of equipment to choose from and costs are low to moderate.

PMR446

PMR 446[8] radios are endemic in the countries that permit them (FRS is perhaps the equivalent in North America) and potentially have a role. They have limited range in most circumstances and require an eye on battery maintenance so they need regular use and charging. They can be very useful on a single site or small area especially if the users are reasonably well-rehearsed in their use. They are available at almost throw-away cost and their specification is such that they all work the same no matter who manufactures them, they are compatible with each other. Sports clubs, schools, building sites and many others are often found using them.

CB Radio

CB[9] is an option for vehicle-mounted and fixed station use, but hand-held radios versions are below optimal and hard to come by. It's fairly popular with off-road (4x4 users) some of whom volunteer in emergency transport or search and rescue groups. The farming community used to use CB extensively also and some still do, though PMR446 has eaten into the former dominance of CB. All these users tend to use the equipment frequently enough to be familiar with its use and know that it works when needed. Reliable range of several miles can be expected with good antennas although fixed-station antennas can be visually obtrusive. There's plenty of suppliers and reasonably knowledgeable installers.

Emerging Technology

You may occasionally come across mention of other licence-free systems called Meshtastic[10] and Meschcore[11] with claims that they are useful in grid-down circumstances. They offer some promise but unless widely deployed and used on a regular basis, they are unlikely to serve emergency situations well (there are some who will strongly argue otherwise, so this point is maybe contentious).

Officially Licensed Systems

The UK body responsible for licensing radio systems is OFCOM. They need to make money so they charge. There are some simple licences available for short-range systems such as building sites, campuses and similar uses which are very affordable (£75 for five years in 2026) but those rarely meet the needs of groups planning for wider-area resilience where a more specialised licence may be required. If radio can do it, you can probably get a licence for it if you have the funding! Few would consider the licence fees extortionate but each case will need to be examined.

There are specialist suppliers of Private Mobile Radio (PMR) equipment who will be able to advise you, although they will also be looking for a sale (naturally). If you have a local Raynet group, asking them for advice may uncover someone who has formerly worked in PMR and can provide guidance with little or no financial self-interest.

Amateur Radio

Amateur Radio typically comes with various classes of licence ranging from easy to obtain[12] but somewhat limited up to licences which permit individuals to build and certify their own equipment and to use power levels that would be dangerous in careless hands. As an example, one aspect of the pursuit is sending signals powerful enough to bounce off the Moon[13] and be received back on Earth. Amateur Radio is for non-commercial use and apart from an examination fee, has no up front or recurring charges.

Amateurs will have access to radio frequencies which can reliably cover any desired range from local to nationwide and are typically experienced in operating the relevant equipment if they possess it - not all are interested in every aspect of radio. They are numerous: unless you live in a remote place there's probably someone quite close to you who has a licence. There may well be a local radio club if you search for it online. Most will be willing to get involved in emergency communications if you cajole them, a few are so interested that they join the relevant local Raynet group and actively plan for events, typically representing only a fraction of those who could do so if they wanted to.

Amateurs who enjoy using two-way radios from their vehicles (very common with the 144Mhz and 430Mhz frequencies) have built an extensive network of radio repeaters, funded by a mixture of subscription, donation and regular bring-and-buy sales. These take an incoming radio signal and simultaneously retransmit it: by locating them on commercial broadcast sites with high towers, their horizon is far away, giving them extended range of 30-50 miles in many cases. So a vehicle 30 miles north of the repeater will be able to communicate easily with one 30 miles south, an all-in range of 60 miles whereas without the repeater 5-10 miles would be the likely limit. Some but not all repeaters have backup power and can be expected to work during power outages. Cambridgeshire Raynet, for example, has specific agreement from the repeater owners in our area that we are welcome to use them in emergencies and exercises.

An example of a particularly effective repeater near Cambridge is the 144Mhz repeater designated as GB3PI[14] which has a map on its page showing coverage from the northern outskirts of London up to King's Lynn on The Wash. The UK has several hundred repeaters of varying coverage, the authoritative reference is at The RSGB Repeater Site[15].

Whilst a licence is required to operate Amateur Radio, UK licencees are specifically permitted to allow 'User Services' to use their equipment in times of emergency or when performing emergency exercises, see footnote.[*2]

Anyone considering adding resilient communications to their plan is advised to contact their nearest Raynet group - the Raynet UK Web Site[16] would be a starting point. Raynet groups are not there just to be called on at the last minute, they will typically be happy to help advise and plan before the event.

Whilst there is no reason why CB and Amateur Radio cannot interwork, it requires the amateurs to use specific CB radio equipment (a requirement of the CB regulations) and since there is already a 30MHz allocation for amateurs, they are unlikely to have legally compatible equipment unless they have a specific interest in CB or a need to interwork.

Privacy, Procedure and Interference

Take Note! Many of the common radio-based options are neither private nor secure, which is very different from a typical portable phone type of communication. Radio is a broadcast medium meaning that anyone with a suitable receiver can listen-in. Also most systems are one-way-at-a-time, so one person speaks while others listen, then the conversation reverses, unlike a phone you don't have bidirectional talking with the option of interrupting the other. This is a little unnatural to those who are unfamiliar with it and experienced radio operators typically

  • adopt a formal radio procedure which structures the communications (terms like 'stand by', 'over', 'roger' etc derive from many years of military experience of doing this)
  • nominate an experienced person to be 'net controller'[*3] to mediate all message passing so that individuals don't talk over each other
  • regularly practise passing messages back and forth to develop communications 'muscle memory' that can be relied on under stress
  • have a well-rehearsed process of relaying messages if not everyone can hear everyone else

The licence-free radios are available to anyone and are sometimes the target of people who enjoy disrupting others' conversations with music, random comments or expletive-ridden language. At large events such as music festivals the limited number of frequencies available to PMR446, which is very popular amongst attendees, may become congested.

Amateur Radio is not entirely free of the interference and antisocial element but most of the time suffers much less from it. Amateurs may well have a wide range of frequencies to choose from and may be better able to avoid it.

Encryption is an option for officially licensed radio systems although it comes with drawbacks around license fees for the technology, management of encryption keys and incompatibility between various manufacturers. Specialist advice will be needed. UK Amateur Radio is generally prohibited from using encryption but with an exemption for when assisting official bodies on emergency business. The exemption is occasionally used (see Essex Raynet[17]). Most radio amateurs will not, however, have access to equipment capable of encryption. Adopting working methods which avoid the need for encryption (no passing of personal details for example) is a typical work-around.

Paying attention to privacy needs to be ingrained if it matters. Without training people will just assume that conversations are private and it can be alarming to hear just how much private detail gets discussed in casual conversations on PMR446 if you listen-in (which is easily done).

Walkie-Talkie Cellphone Apps and Devices

The one-to-many aspect of a group of people communicating by radio, where everyone can hear every message, can be very beneficial in providing situational awareness to a team. This is in direct contrast to the private one-on-one conversation that telephone conversations provide.

Although not obviously resilient in times of emergency, various smartphone apps such as Zello[18] and its many alternatives provide group voice messaging. They carry the voice over data connections and appear to have substantially replaced mobile radio equipment for many classes of users. The appeal is obvious, rather than having to have specialised equipment and radio licences that cover the country, just use a smartphone app and a data subscription. The low cost of entry is appealing to groups which otherwise could never have considered a private communications system - voluntary search-and-rescue teams, for example. A further advantage is that casual snoopers are unlikely to intercept any messages passed unless that feature has specifically been enabled.

IF you don't need resilience in the face of power failure and can rely on a good data service being available, this approach is appealing.

A number of manufacturers now make "PTT over Cellular" (PoC) devices - these look and work like a typical walkie-talkie device but use cellular and/or WiFi data as appropriate. Many are smartphones and can run typical apps as well. A specialised industry sector is growing up around them either as equipment alone or more broadly as managed communications systems for corporate users. Enhancements may include designated talkgroups, text messaging, private calls, GPS tracking, lone worker protection and more.

Although vulnerable to wide-area failures this has its place in a layered communications plan which makes use of high-level services if they are available and falls back in tiers as preferred methods fail. Search and rescue groups as mentioned above, for example, may use PoC devices when cellular services are available but fall back to point to point radio systems when not.

References

  1. ^ Wikipedia entry on Radio
  2. ^ Wikipedia entry on speed of light
  3. ^ VOACAP radio propagation prediction software
  4. ^ Wikipedia entry on radio antennas
  5. ^ Wikipedia entry on the solar cycle
  6. ^ Wikipedia entry on Starlink satellite Internet/data access
  7. ^ Report into Storm Desmond by the Royal Academy of Engineers
  8. ^ Wikipedia entry on PMR 446 Radio
  9. ^ Wikipedia entry on CB in the UK
  10. ^ The meshtastic low-power off-grid radio system
  11. ^ The Meshcore low-power off-grid radio system
  12. ^ Essex ham radio licence training course
  13. ^ RSGB web page re moonbounce communications
  14. ^ Cambridge Repeater Group GB3PI repeater
  15. ^ RSGB databae of amateur repeaters in the UK
  16. ^ Raynet UK website
  17. ^ Essex Raynet website
  18. ^ Website for the Zello software

Footnotes

  1. ^ As fibre replaces copper connections even to domestic homes, older analogue landline phones are being replaced by digital equivalents or analogue-to-digital adapters.
  2. ^ Extract from the amateur licence conditions: "User Service" means the British Red Cross, St John Ambulance, the St Andrew's Ambulance Association, the Royal Voluntary Service, the Salvation Army, any Government Department, any 'Category 1' responder, and any Category 2 responder as defined in the Civil Contingencies Act 2004;
    This presumably means that a non-licensed 'civilian' resilience group could affiliate to, say, the Royal Voluntary Service, and thereby legitimately gain supervised access to amateur radio services with the help of a local licensee. The local licensee could be one of their own members who has put in the estimated 10-12 hours study it takes to obtain the lowest level of licence.
  3. ^ 'Net' is a long-standing term used to refer a group of people mutually communicating by radio