Resilient Group Communications

Introduction

Note: this article is predominantly relevant to the UK, though most of the information will be applicable in many other areas also.

Telephone (fixed or cellular/mobile) and internet based messaging is an integral part of life. These depend on advanced technical infrastructure outside of our own direct control and which is itself dependent on electrical and communications supplies from yet other organisations - a complex web of dependencies. If any of these fail - and there is a particularly high dependency on electricity - any of our own communications which depend on them are likely to be seriously hampered.

For some of us that will simply be inconvenience but for essential services the situation will be worse. Emergency 'blue light' services typically do have resilient communications with backup power but they will not be able to help everyone who normally relies on cellphones and instant messaging. There are some stand-alone options that can be employed to bring full control of communications back into our own hands, the simpler and thus more likely ones are explored in this discussion.

A typical solution would consist of individuals using battery powered hand-held (walkie-talkie) equipment, often coordinated through a base station to form the communications hub.

All the options discussed here depend on the use of radio technology. Anyone who uses a cell (mobile) phone is used to this already - the phone uses radio to communicate with a base station, behind which lies the technology for call set-up, billing, and transfer of the connection between base stations if the user is moving. Because of this we are also familiar with situations where there is no signal e.g. railway tunnels, dead spots in urban areas and, in rural areas, larger dead spots at times too. These are normal and unsurprising aspects of any radio-based communication system.

A short summary is next for those short of time, followed by more detailed information.

Executive Summary/Conclusions

Limited-range (single-site, say 1km max) resilient communications between up to maybe 30-50 individuals is relatively easy to arrange at modest outlay. Coverage for a similar number over a wider are of operations of 5-10km radius is achievable with more planning but still feasible without extensive preparation.

Wider area (say county-wide or further) coverage or for larger numbers of users is a significant challenge. Solutions exist, of course, but are far from simple and require planning not only for equipment but staffing also and regular exercises to ensure readiness. Satellite phones may be an important consideration where the cost of line rental and calls can be justified.

The only realistic solution for internet access during infrastructure failure is satellite, for example (but not limited to) Starlink^[1].

As the author of this item, I have personal experience of arranging and participating in exercises using fallback communications and speak to others who share it as an interest. From a Civil Contingencies point of view I'm not aware of any well-developed planning in the UK on an official basis apart from that done by the designated emergency services: Police, Ambulance, Fire and Rescue, Coastguard.

Any other group or organisation wishing to set something up will have to do it for themselves, though they may get help from existing volunteer groups on a small-scale and local area only basis. Nothing will happen without planning, equipment acquisition and prior preparation including some training.

Whilst the provision of equipment alone may work for short-term emergencies, logistics support will also be needed for staff over longer durations - obviously their health and welfare - but also practical matters like power or battery charging as necessary and spare/replacement units.

Discussion

Options

There is a range of options for radio communications. Here, we look at the simple and relatively low-cost options that can easily be deployed when needed in an emergency.

Key factors when choosing any option are:

What features does it have?
What training and procedures (if any) are needed to use it?
What range does it have?
What licensing is required?
What does it cost?

Features

Simple radio communications differs from telephone usage in important ways:

Telephone conversations are usually one-to-one with each person able to interrupt the other. With simple radio communications there is a group of individuals, all potentially able to hear each other and only one can talk at a time. You are either talking OR you are listening. The radio will have a push-to-talk button - push it and talk, release it and listen.
There is no dialling or call set up. Each radio typically has a number of 'channels' that can be used (it may be preset to one only) and the group of users all use that channel and hear all that is said even if some of the messages are not personal for them. Channels resemble instant messenger group chats, without history - if you miss a message when it's sent, it's gone.
Telephone conversations are assumed to be private. Radio is public, anyone could be listening to you. If another unrelated group nearby happens to pick the same channel as you, you may well interfere with or confuse each other.

Training and Procedures

Assuming that your users have a specific need for communication, you will want it to be accurate and reliable, especially under difficult operational conditions which may include pressure and stress. It's instructive to hand a few radios to a group such as scouts/guides or hiking parties and then put them under pressure: without agreed procedures and training the communications rapidly becomes chaotic and ineffective.

Simple procedures which have been explained before hand will make a big difference. There are well-established conventions for organising group communications and a discussion of those is given at the end of this document. Users can be trained in just a few minutes (though longer is better) and, ideally, reasonably regular exercises can be arranged to help embed good practice. This cannot be ignored but it is not onerous and in general people learn it quickly and easily.

There is also a logistical issue of ensuring that battery-operated equipment has suitable recharging opportunities. This may be overnight if operations are not 24 hours, or you may employ a system of exchanging charged batteries for depleted ones. Consideration should be given to the carrying of spare full batteries by individuals if charging or swapping will be difficult for them. Equipment breaks or gets lost: you will need some spares.

Range of radio equipment

Everyone wants to get an exact answer on range but sadly this is impossible to give. It's important to understand why. Factors affecting the range of equipment are

the radio frequencies the equipment uses
the power of the equipment
the quality of the antenna (this is the part that 'launches' and receives the radio signals)
the terrain where the equipment is being used

A brief note on each follows in ascending order of importance.

Radio frequencies

Radio waves and light are essentially the same thing - a form of vibration that travels through space. Light vibrates at extremely high frequencies, usable radio waves at much lower ones, analogous to music with high and low notes. Just as low pitched sounds travel further than high pitched ones (foghorns are always low-pitched), radio waves can, unlike light, at least partially penetrate obstructions like bushes, trees, buildings and so on. Different radio frequencies have somewhat different characteristics meaning some are better for long distances, some for short.

Typical short-range communication is done using radio frequencies of 400-500MHz. Efficient antennas (ideal length around 30cm) are easily mounted on poles or vehicles and there is widespread availability of low-cost equipment. Hand-held devices are affordable and vehicle/base station equipment is by no means expensive.

Power of equipment

The power of the equipment has a direct impact on the range of the signal but only up to a point. For small hand-held radios the power is always kept to a minimum for safety reasons and to preserve battery life. Radios mounted in vehicles or fixed ('base') stations are less constrained and typically have more power available and hence greater range, but in all cases there comes a point of diminishing returns where adding more power has at best only marginal effects on the range.

Antenna quality

The antenna has a large and direct impact on the range of the equipment. It's simply not possible to fit a good antenna to a handheld radio, they are always heavily compromised. Vehicle and fixed stations can have much better antennas and can potentially mount them higher-up, which (see terrain below) dramatically affects performance.

Terrain

Terrain means geography and surrounding features. At the radio frequencies most likely to be used, woods, trees and shrubbery only have limited effects on range, but large buildings (say in the centre of a city) will definitely have an obstructive effect. Large pieces of geography such as hills can entirely block radio signals. Barely visible ridges or hillocks can make the difference between good signals and no signals. Torrential rain has also been observed to affect range though it's fortunately a rare occurrence.

If the antenna can be positioned well above ground this usually has a transformative effect on the range that can be achieved. Simple low-power hand-held radios which can manage at best a few hundred metres in a built-up area can sometimes, from hilltop to hilltop, achieve ranges of tens of kilometres instead and record distances of hundreds of kilometres have been achieved under ideal conditions. Similarly, moving from ground-level to the upper floors of a building will greatly alter the effective range of a hand-held radio.

There is just no answer to 'what range will I achieve?'.

Range in Practice

For hand-held to hand-held radio, the effective range is particularly limited by their inherently poor antennas. It may be adequate for a single building or a single site like a concert or festival or sporting event but in general it's unwise to expect more than some hundreds of metres and dead spots are likely at the limits.

Typical ranges achievable with a mix of handheld and high-powered, well-located base stations tend to be of the order 5-10km or maybe double that for vehicle to base station communications.

So, for all but the least demanding situations it's normal practice to allocate hand-held or vehicle-mounted radios to individuals who are then coordinated by a strategically placed base station. The base station ideally has an elevated antenna located somewhere near the geographic centre of operations although in exceptional cases the base station could simply be another hand-held (or vehicle) located high up.

ALL messages go via the base station to avoid the situation where 'A' wants to speak to 'B' but they are out of range of each other. In many situations there will in any case be little need for A-B conversation, but instead individual units will be reporting or querying operational control which will be done via the base station. When needed, more than one base station can be employed for greater geographic coverage provided that good procedures for calling and message-passing are understood by all concerned, implying slightly more need for training.

Wider areas are not easy to cover with simple equipment operated by untrained people. If greater distances are essential then solutions can be found but not without planning and effort. Some radio frequencies will, for example, give highly reliable communications over hundreds of miles: prior to ubiquitous internet and fixed or satellite communications they were extensively used for commercial and government or military purposes, nowadays they remain in use mostly by specialised operators. Planning fallback communications over ranges of multiple tens of kilometres is a specialised subject. It's entirely possible, but it's expert territory.

Licensing

Radio communications are generally subject to licences. Some low-powered hand-held equipment which conforms to suitable specifications is available under a general licence which means it can be purchased and used by anyone, but more powerful equipment will only be available after applying fo a licence to use it. The licence is typically granted for type-approved equipment to a specific organisation or body which then decides which personnel are allowed to use it. A different type of licence is granted to individuals in the case of Radio Amateurs ('hams') who have wide discretion in the types of equipment, radio frequencies and power that they use.

Cost

Naturally there's a range of costs. The licence-free handheld equipment at the simpler end of the scale can often be bought in bulk packs though the very lowest cost items may be flimsy and poor quality. Costs in 2022 are of the range of £20-50 per unit. Higher quality licensed handheld radio equipment may cost broadly double that. Vehicle or base station equipment again varies, maybe around £100-200 per unit depending on specification and power. Handheld devices typically come with batteries and chargers included, though it may be wise to budget for spare devices (breakage) and extra batteries if extended duration is needed.

Base stations and vehicle mounted equipment will also need cabling and antennas installing so a modest budget for installation will be required.

Types of Equipment

Licence-free Handhelds

handheld radio Equipment known as PMR446^[2] is a small low-powered handheld 446MHz radio sold as a consumer item needing no licence, as in the image (though they come in numerous styles). It must conform to particular specifications including an integral antenna (the black stub top left). These are specifically designed for short ranges and are commonly used for fun and leisure activities. When first released there were 8 channels available, later expanded to 16 - if buying new, get the 16 channel versions: the upper 8 channels are less congested. They are available in a range of qualities, some with built-in rechargeable batteries or some using disposable or separate rechargeable batteries, in which case they will usually be AAA or AA size.

When only short ranges are required these are capable units, but as it's not possible to get a licence for a base station, they are not particularly useful as part of wider area operations other than as an adjunct.

Handheld radios usually support a feature often mis-described as 'privacy' (CTCSS or DCMS)^[3] codes which, if set, will cause the radio only to receive a transmission with a matching code. If the same channel is in use by two separate groups with differing codes, group A will only hear group A messages (because of the code) and similarly with group B only hearing group B messages. A radio with no code set will hear everything that's in range.

There is also a digital version of PMR446 which is supported by few commercially available radios, costs more and is unlikely to appeal.

Licensed Handhelds

Licensed handhelds can be significantly more powerful than their unlicensed counterparts and are typically preferred by professional users.

In the UK, licences are handled by OFCOM and a range of licences are available^[4]. Wide area fixed and complex systems up to private cellular systems can in principle be licensed but for occasional standby use the 'business light' licenses are probably most relevant. As an example, in Cambridgeshire the volunteer RAYNET^[5] group uses an OFCOM licence to provide licensed handsets and a mobile base station with a pump-up mast/antenna to provide communications at user events and emergency call-outs.

Handheld to base-station range is typically of the order of a few km, but bear in mind the heavy caveats already mentioned with respect to range.

Licensed Vehicle-mounted Units

The OFCOM light licences do not preclude the use of vehicle-mounted equipment of modest power and, although OFCOM suggests that the licenses are intended for use in areas of limited range (e.g. 1km) there is no specific limit imposed. Vehicle mounted systems could be expected to obtain 2-3 times the range of handhelds.

CB Radio

An alternative to the 400MHz type of radios is the licence-free CB radio band at 27MHz. Legally in the UK CB is limited to 4 watts transmitter power and typically has characteristics not dissimilar to those already discussed above in terms of range. Antennas need to be substantially larger at this lower frequency (ideal length 5m) which means that vehicle-mounted antennas are not ideal and hand-held devices perform badly (so badly that they are very hard to find). Because of this CB is typically only used by base stations and vehicles and has an expected range of, say, up to 10km.

CB antennas are somewhat less affected by height above ground.

Base station and mobile CB equipment is easily available at modest cost, it may have a place in a plan for resilient communications and should not be discounted. In the UK, CB equipment is usually switchable between two sets of 40 channels, offering 80 channels in total. Whilst there is some hobbyist use in certain areas, the majority of those channels are very rarely used.

Data Communications

starlink antenna in use The main thrust of discussion here has been on voice communications between individuals. If organisations need to exchange documents, emails and so on, then they will need something resembling Internet access. There are a number of providers of satellite-based internet as an alternative to broadband. In particular the use of a recent entrant to this arena - Starlink^[1] has apparently transformed the battlefield for the Ukranian armed forces with reliable internet access available under pressing conditions. If internet-like access is essential then satellite is an important option to consider. The image shows a Starlink antenna mounted on a tripod at an outdoor film set.

Satellite Phones

An alternative to handheld radios, satellite phones are often used by explorers, long distance sailors and civil rescue groups. Satellite phones come in a variety of price and coverage options and in general offer a solution to the problem of range. Subscription fees tend to be high and thus to preclude them from being a general solution except for staff who have a pressing need to be in contact and for whom the monthly line rental and call cost is justified.

The "Livng without Electricity"^[6] report drily notes that in a case where satellite phones had been provided it was discovered that users, when pressed, didn't know how to use them, emphasising the need for regular training and exercises.

Cooperation with Amateur Radio Emergency Groups

Generically referred to as 'Amateur' radio users, a significant number of people hold licences for high-powered and long-range equipment for personal and hobby interest. Some are indeed amateur, others are communications professionals who use their licenses for a range of leisure purposes. Amongst them are organised groups with an interest in resilient communications. In the UK, amateur licence holders are specifically authorised to assist essential services on request.

As well as being experienced operators of radio equipment, amateurs will often have access to devices known as repeaters. Repeaters are typically located at highly advantageous locations (often on commercial masts at broadcast sites), receiving messages on one channel and simultaneously rebroadcasting them on another. Repeater-to-handheld ranges of 20-40 km are common, perhaps double that to vehicle and base station users.

Repeaters are re funded by subscription from hobbyists and not typically provided with backup power. If a repeater was to be used as part of an emergency plan, this would need to consider the issue of backup power and the duration of expected power outages.

More specialised radio equipment makes use of what used to be called short wave radio frequencies. Many but not all amateurs possess and use this type of radio which can be used reliably to communicate anywhere within the UK and near or mid Europe. Antennas for this are 30-80m lengths of wire and usually only employed by fixed stations, though field-deployable is also possible. A more detailed discussion of short wave capabilities is available here.

In the UK, the RAYNET^[5] organisation is specifically set up to provide fallback or emergency communications by volunteers from the amateur community. In practice, RAYNET groups vary considerably in the numbers and enthusiasm of the volunteers. The more active groups will typically (but this varies a lot) have a number of regular events at which they assist such as outdoor leisure and social events as also cooperating with search and rescue groups.

The availability of much higher powered equipment as well as repeaters means that amateur groups can potentially provide very much improved areas of operations than the other options discussed so far. However, established groups are usually scaled only for small numbers of users and in an emergency situation lasting more than a few hours would rapidly run out of personnel to rotate.

Whilst it would probably be possible to enlist larger numbers of licensed operators to participate in exercises to ensure readiness this will not happen spontaneously and would require effort and energy to ensure that it happens.

Training and procedures in practice

It's already been noted that simply handing walkie-talkies to untrained users rapidly results in confusion. There are very well understood and established procedures which can be adopted to manage this situation and users can be trained quite quickly in the basics. These will include:

The use of 'callsigns', unambiguous identifiers for each position or role, rather than personal names
Designation of main and fallback channels and how and when to use them
Procedure for calling and, if part of the procedure, switching to a working channel
Designation of one station (typically the base station) as the controller of the group
A procedure for requesting and obtaining permission to speak (to avoid long transmissions which clash with each other)
Procedures for acknowledging receipt of information, requesting retransmission and for the beginning and end of each message
The avoidance of easily confused numbers like sixteen/60 - done by giving each digit, e.g. 'sixteen, one six' or 'sixty, six zero'
The basics of simple phraseology like 'roger', 'over', 'stand by', 'out', 'say again' and related terms
Emergency procedure for safety-of-life messages which override normal communications

Messages have to be kept short and to the point. Long messages of no relevance to you are distracting if you are doing a complex job but obliged to hear them. If this is a frequent and necessary occurrence it may require the use of one or more separate channels used for longer conversation (this is common with ship-to-shore radio, for example - a 'calling' channel to get attention and one or more 'working' channels for detailed discussion).

Here is not the place to provide a tutorial, it's enough to point out that all groups which use radio communications in any but the most relaxed of leisure contexts find it essential to adopt a procedure similar to the above. A short course in the basics - backed up by occasional practice - makes for simple, reliable and stress-free communication, allowing the users to concentrate on their jobs.

Conclusions

See 'Summary' at the top of the page for concluding remarks.