The use of the radio spectrum in Europe is determined by a range of different organisations. At the truly international level, the ITU dictates which services are allocated which parts of the spectrum in its Radio Regulations which are updated every 3 to 4 years as the result of the World Radiocommunications Conference (WRC) at which every country in the world's regulators sit down and agree on any changes. At the more regional level, CEPT propose and make decisions on the use of spectrum in Europe. In the case of both the ITU and CEPT, several working groups are established to consider different topics such as fixed links, mobile services and satellite services.

A recent meeting of CEPT/ECC Working Group PT-A which took place in June in Prague, Czechia, was considering the items that should go on the agenda of the 2023 WRC, as these need to be agreed at the 2019 WRC to be held later this year. At this meeting, the French spectrum regulator, the ANFR, updated a proposal concerning:

an agenda item for new non-safety aeronautical mobile applications.

Non-safety aeronautical mobile services are likely to consist of things such as the remote control of (military) drones. As a result of this submission, the meeting has proposed an item that will be taken by CEPT member countries to the next WRC which states:

New non-safety aeronautical mobile applications will support applications like: imagery, video, fire and border surveillance, environment monitoring, traffic/disaster monitoring. Such applications require ground to air, air to ground and air to air, communications on-board manned and unmanned aircraft. Use of innovative sharing methods may be considered to ensure the protection of existing services while offering the possibility to have access to new frequency bands. Several frequency bands are proposed for investigation within different ranges in order to meet the various operational requirements for new non-safety aeronautical mobile applications.

It is proposed to study the bands 162.0375-174.000 MHz, 862-874 MHz and 22-22.21 GHz in order to evaluate the possible revision or deletion of the "except aeronautical mobile" restriction and the bands 144-146 MHz, 5000-5010 MHz and 15.4-15.7 GHz for possible new allocations to the aeronautical mobile service.

Hidden amongst this is a potential time-bomb for radio amateurs. The French administration is effectively proposing that the 2 metre amateur band (144 - 146 MHz) which is currently allocated for the exclusive use by radio amateurs, should be shared with non-safety aeronautical mobile services. Note that this is already the case in China and that in Region 1 (Europe) the spectrum immediately below the 144 MHz band is already allocate for Aeronautical Mobile services. The proposal does not state whether the new allocation should be on a secondary basis (in which case radio amateurs would continue to be protected from interference) or whether it would be on a co-primary basis (in which case both sets of users would have equivalent interference protection rights).



Wireless Waffle understands that the proposal was originated by French defence manufacturer Thales, and that their preferred outcome would be a co-primary allocation. Should this happen, notwithstanding the fact that there would be an interferer in the 2 metre band, the aeronautical services, if they suffered interference from amateurs, could them potential claim protection. It is not completely impossible that as a result of this, the amateur service could be either reduced to secondary status, or told to leave the band. Such an outcome would take at least 12 years, as it would first have to be put on the agenda for a future WRC (which could not be until at least 2027), then studied, before a decision could be made (at the eariest 2031).

Should radio amateurs be concerned. In a word, YES! The 2 metre band is very heavily used and is one of the only primary and exclusive amateur radio allocations that exists. A number of other amateur bands have recently been reduced or lost to other services (e.g. 2.3 GHz, 3.4 GHz) and there is also consideration of removing the amateur service from the 23cm band from 1260 to 1300 MHz to protect satellite navigation systems. However inconceivable it may be that the 2 metre band could go the same way, it is not impossible.

What can radio amateurs do? It is the national radio spectrum administrations who attends the CEPT/ECC meetings and represents the views of their country. In the first instance, therefore, amateurs should write to their national regulator (e.g. Ofcom in the UK) and express the importance of keeping the 2 metre band primary and exclusive for amateur use.

International organisations such as the IARU and national organisations such as the RSGB get involved to support the interests of radio amateurs, but this can only succeed if the national administrations listen empathetically.

If national administrations fail to support the amateur service, the next step would probably be for radio amateurs to protest outside CEPT/ECC meetings to try and demonstrate to CEPT just how strongly they object.

Conduct a web-search for topics relating to 5G and on many occasions the answers which get returned are nothing to do with the next generation of mobile services, but relate to 5 GHz, which is one of the frequency bands used for WiFi (as well as several other technologies). It seems that both terms being of a wireless nature, those clever search engines are yet to be able to fully distinguish between them.

But there is more... If that isn't confusing enough, there's also a technology known as G5 which is designed to perform the job of allowing vehicles to communicate with each other, known as vehicle-to-vehicle (V2V) communications, and with infrastructure (such as traffic lights) known as V2I. And to really throw the cat amongst the pigeons, the frequency band used for G5 is 5 GHz (5850 - 5929 MHz). Got that?

So, just to be really clear and helpful in exactly the way that Wireless Waffle always isn't, here are some bullet points which don't make everything far more translucent:

• 5G is the term used for the next generation of mobile technologies which will follow after 4G (LTE). The technology involved is also known as New Radio (NR).
• 5 GHz is a range of radio frequencies often considered as being 5150 - 5925 MHz, which are used by a wide variety of applications including WiFi, 4G (including LTE-U, LTE-LAA and MulteFire) and G5.
• G5 is a vehicle communication technology designed to enable Intelligent Transport Systems (ITS) such as autonomous vehicles.

And now you know. So if Mr Google comes a-calling to this here web-page, hopefully he will be enlightened and future search results will no longer confuse these very different technologies!

A while ago Wireless Waffle added an FM DX logbook listing reception of far distant (a.k.a. DX) FM radio stations which have been received in the UK at various times. Reception of such stations has also been discussed before in particular with reference to sporadic-E propagation.

FM stations being received over a long distance by sporadic-E tend to be very strong, and can often overwhealm reception of local stations. Those being received through tropospheric ducting are often somewhat weaker.

It was a surprise, therefore, on a recent drive around London's orbital motorway, the M25, whilst listening to community station Kane FM at a distance of approximately 13 km from the transmitter, that french station France Inter on the same frequency of 103.7 MHz, became stronger. So much so, that the radio in the car decoded the RDS of France Inter and switched between 103.7 and 99.6 MHz where a second transmitter could be received.

The transmitter of France Inter on 103.7 MHz uses a massive power of 400 kW from a site in Lille (approximately 260 km away). It is actually one of the highest powered FM transmitters in the whole of Europe. The France Inter transmitter on 99.6 MHz uses a transmitter power of 50 kW from a site in Caen (approximately 225 km away). If you consider the free space path loss from these sites, and their transmitter power, you can roughly calculate the expected signal strength that each transmitter would produce.

Radio Station	Frequency	Power	Distance	Path Loss	Field Strength
Kane FM	103.7	25 W	13 km	95 dB	56 dBuV/m
France Inter (Lille)	103.7	400 kW	260 km	121 dB	72 dBuV/m
France Inter (Caen)	99.6	50 kW	225 km	120 dB	64 dBuV/m

Assuming free space loss, therefore, the signals from France would be 8 to 16 dB higher than those from the nearby Kane FM transmitter.

However, this is nothing like reality: free space path loss gives a result which would represent the strongest possible signal that could be received. Of course none of the signals would be propagating in this way, as there would be innumerable obstacles along the way that would deviate wildly from 'free space' and the signals would come nowhere near these values, especially those that have travelled 200 km or more from France. Note that various studies have indicated that for reception in a car, a signal strength around 40 dBuV/m is needed suggesting that the additional path loss caused by propagation effects would have been in the order of 16 to 32 dB, which seems reasonable.

FM receivers have an effect called the 'capture ratio'. In general, if two signals are on the same frequency, and one is more than around 3 dB stronger than the other, then the strongest signal will win-out and the weaker one will disappear. So at least it is clear that the signal from France Inter on 103.7 was a few dB stronger from that of Kane FM.

None of this is groundbreaking nor even necessarily that interesting, but it does suggest that the actual path loss obtained during reception by tropospheric ducting can be relatively low. And for radio stations in areas prone to tropospheric ducting (predictions of which can be found on Willam Hepburn's excellent web-site), using a few extra dB of transmitter power may be necessary to ensure reliable reception. Stations, for example, on either side of the Arabian Gulf often use tens of kiloWatts of transmitter power even to provide coverage of just one city, as problems with ducting of signals from the other side of the Gulf are an almost daily occurrence.



Of course, the converse is that using more power then causes increased interference to those on the other end of the duct. Which in turn requires them to turn up their power to combat the problem. Which makes the problem worse. And so forth...

Back in December of 2016, the UK Government's National Infrastructure Commission published its 'Connected Future' report. It recognised that:

government must take responsibility to secure our digital future ... Government must ensure we have the infrastructure in place to deliver 5G

Amongst the various proposals in the report, many are based on the recognition that 5G will require access to orders of magnitudes more base station sites than are currently deployed for 4G.

This makes a lot of sense. Local planning restrictions already hamper the roll-out of mobile services, not just because local councils think that cell sites are ugly, or even that they damage the environment or health, but the application procedure to get permission to install a site varies wildly from one council to another. Simplifying, harmonising and streamlining the process is essential if the UK, or indeed any country, is going to benefit from whatever it is that 5G is going to offer.

It seems rather short-sighted then, that the Welsh Government is still pondering a change to what are know as Permitted Development Rights (PDR) to allow mobile operators to build masts with a height of 25 metres (82 feet) with reduced planning requirements. At present, in Wales, operators are only allowed to extend the height of their masts to 15 metres (50 feet), whereas in the rest of the UK, the limit is 25 metres.

Wireless Waffle has previously discussed the relative merits of increasing transmitter power compared to increasing antenna height and demonstrated the importance of antenna height. In an area such as Wales where the difficulty in providing coverage is exacerbated by the hilly terrain, and where a large number of mobile 'not-spots' exist, antenna height is of even greater importance. The reluctance to increase the permitted tower height comes in stark contrast to a previous move by the Welsh Government to invest £150 million in trying to provide coverage in these not-spots.



There is no doubt a fear that higher masts will make the countryside look ugly or cluttered, but the counter-balancing effect is that taller masts, means fewer masts. Imagine how many TV transmitter towers there would need to be if their height was limited to 15 metres. If Wales is to rise out of the valleys in terms of mobile coverage, the Welsh Government needs to act quickly, i.e. before 5G comes along, to ensure that the existing not-spot problems are not further heightened (see what we did there?)

As they say in Wales: "Nid yw tegell llawn caws yn cael ei ddefnyddio i ffôn symudol gyda chalon wedi'i dorri."