Wireless Waffle - A whole spectrum of radio related rubbish

Ding dong, that's my song...signal strength
Saturday 27 January, 2018, 09:04 - Spectrum Management, Much Ado About Nothing
Posted by Administrator
It seems that we, here at Wireless Waffle are having a bit of a spate of 'told you so' type events at the moment. Last month we spotted that Vodafone had been rapped over the knuckles for their crafty roaming fee shenanigans. Now we have spotted that Ofcom have been called out to assist drivers who couldn't lock or unlock their cars due to radio interference.

key car lockedOn various occasions we have discussed how straightforward and relatively widespread the jamming of the frequencies used for your car keyfob is. Last time we discussed this it was because some miscreants had latched onto the idea and were stopping people locking their cars so that they could easily break in (more like stroll in) and take whatever they found in the glove compartments, foot wells and boots of the rich and not-so-rich.

ofcom logo 1The Ofcom story is even more worrying as it suggests that jamming these devices is far easier than even we though possible. In addition to the car keyfobs we are so keen on discussing, the same frequency range (433 MHz) is also used for a wide variety of other wireless devices including wireless doorbells. These devices are relatively low power (10 milliWatts) and the idea is that they shouldn't interfere with each other as the range of transmission is very small. It seems, however, that a button on one such doorbell got stuck in the 'on' position, meaning it was constantly transmitting. This was enough to stop people in the vacinity locking and unlocking their cars. Thankfully, the brave Ofcom engineers were able to track down the problem and sanity was restored. Hurrah for Ofcom!

Far be it for us to opine on the implications of this, but taking the earlier example from the BBC in which miscreants were jamming car locks but haven't Ofcom just provided these folk (and others with a similar inclination) with a simple, cheap and undetectable means of achieving the same outcome?

Just get hold of the push-button part of a wireless doorbell, put this in your pocket, and wander around a car park where posh cars park (maybe even buy a hi-viz jacket so it looks as if you are meant to be there). If it's a supermarket car park, collect a few trollies whilst you're waiting. When a particularly rich looking owner appears, go and stand close to their car and as they get out and get ready to press the button on their key to lock it, activate the wireless doorbell button. 'Hey presto', the car won't lock and you will be able to help yourself to their Gucci loafers and other luxury goodies.

From a radio spectrum management and perhaps more specifically a Wireless Telegraphy Act perspective, no law has been broken. From a Theft Act perspective, however, you still stand to be charged (or sit, depending on the layout of the court room).

Thanks Ofcom!

ding dong thats my song

Posted using my gold-plated iPhone X, whilst wearing Gucci loafers and sipping Bollinger RD '85 on my luxury yacht moored in Saint Tropez with my 3 Aston Martins parked alongside.
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Vodafone rapped over knuckles for roaming scamsignal strength
Saturday 23 December, 2017, 18:01 - Spectrum Management
Posted by Administrator
Back in June of last year, Wireless Waffle discussed the fact that Vodafone had hiked their roaming charges in a number of countries, making even a simple text message cost a fiver or more.

ofcom chastises vodafoneIt seems that we were not the only ones to notice this but that the powers that be took a dim view of it as well. As a result, Vodafone has been forced by the telecoms regulator Ofcom to allow its customers to end their contracts early, if they had been duped into the roaming scam.

On the one hand it's hard to feel sorry for Vodafone for sneaking in these additional roaming charges, when it was faced with a total loss of roaming income from anyone going to Europe as a result of European Commission Decision (EU) 2016/2286 which forces all EU mobile operators to abolish roaming charges between Member states, often dubbed the 'roam like at home' decision. On the other hand, it was a pretty underhand move, especially as the only notice that some Vodafone customers had was a text message - and who bothers to read text messages from their operators?
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Radio Caroline 648 kHzsignal strength
Wednesday 22 November, 2017, 15:31 - Broadcasting, Licensed, Pirate/Clandestine
Posted by Administrator
radio caroline 648 khzWireless Waffle previously sang the praises of the boat trips to visit the Ross Revenge, the home of former radio pirate, Radio Caroline. We also noted that they had been awarded a licence to operate a 1 kiloWatt transmitter on 648 kHz in the Suffolk and north Essex area.

Well, it seems the engineering bods on the east coast have managed to get it together, and recently test transmissions on 648 kHz were spotted by a number of listeners, such as a DXer in Humberside who posted the video below on YouTube.



Though you may not be able to interpret the waterfall display shown on the video, what you see is the Radio Caroline signal in the middle. The two bright lines either side represent radio stations on the adjacent frequencies (639 and 657 kHz respectively). Normally, for AM broadcasting, each station would be allowed to occupy half of the bandwidth between its assigned frequency and the adjacent channels, meaining that it would extend +/- 4.5 kHz either side of its centre frequency. It is this limitation they gives medium and long wave broadcasting their characteristic 'muddy' sound, as the limitation in spectrum also restricts the amount of audio bandwidth that can be transmitted.

It's therefore notable that the Radio Caroline transmission on 648 kHz extends far closer to the adjacent frequencies than 4.5 kHz. It appears closer to +/- 6.5 kHz wide (or maybe even more). This would allow the station to transmit a wider audio bandwidth and thus sound a little 'brighter' on-air. Such derogations from the norm are not unusual as the medium wave band has become emptier, as there is more space for stations to spread out and sound better.

As an example, the three audio clips below have been filtered with different bandwidths. Just click on the relevant button to hear the difference (note that this doesn't work in all browsers.

Audio BandwidthPlay
15 kHz, stereo (FM Stereo)FM Stereo
6.5 kHz, mono (extended bandwidth AM)AM 6.5 kHz
4.5 kHz, mono (standard bandwidth AM)AM 4.5 kHz

trevor radio carolineGiven that of the neighbouring frequencies, the nearest stations on 639 kHz are in the Czech Republic and Spain (previously crowned the queen of medium-wave broadcasting) and on 657 kHz in Spain (again) and North Wales, it seems unlikely that the additional bandwidth being used by Radio Caroline will give any problems and we are sure that listeners will enjoy the cleaner, brighter sound that they will have on-air.
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Digital UK Magic Spectrum from Nowheresignal strength
Tuesday 21 November, 2017, 10:27 - Broadcasting, Licensed, Spectrum Management
Posted by Administrator
digital uk nov 2017Digital UK, the organisation responsible for promoting digital terrestrial television in the UK, has recently published a white paper it commissioned from consultants Aetha and Webb Search entitled 'The defragmentation dividend: A more efficient use of the UHF band'. The paper hypothesises that by re-organising the UHF (e.g. sub 1 GHz) spectrum available to mobile operators, it would be possible to use it more efficiently and deliver more service from the same amount of spectrum.

The paper identifies the fact that, at present, the 'digital dividend' spectrum (e.g. that which has been released from television broadcasting due to the increased efficiency of digital transmission over its old analogue counterpart), is broken up into a number of fragmented pieces whose usage is not optimum. This is certainly true: the figure below shows the current set of allocations within the frequency range 694 - 960 MHz.

694 960 mhz plan

The mobile allocations at present are as follows:

BandUplink (MHz)Downlink (MHz)Amount (MHz)Notes
900 MHz876-915921-96078Including GSM-R
800 MHz832-862791-82160
700 MHz (a)703-733758-78860FDD
700 MHz (b)738-75315TDD or Downlink
TOTAL213

In addition there is approximately 29 MHz set-aside for short-range devices. Thus, of the total of 266 MHz of spectrum between 694 and 960 MHz, 213 MHz (80%) is allocated to mobile services, 29 MHz (11%) for short-range devices leaving 24 MHz (9%) 'empty' (mostly for guard-bands to protect services on adjacent frequencies from interfering with each other). The theory is that by re-arranging the band, it is possible to use all of the small gaps that currently exist between the various mobile allocations (e.g. the 9% that is empty) for more mobile services.

One of the problems of the plans proposed in the report is that although they increase the amount of spectrum for mobile services to up to 250 MHz in their most extreme case, they also reduce the amount available for short-range devices from 29 MHz to just 16 MHz. Whilst you may be thinking, "isn't mobile a better use of spectrum than short-range devices", the fact is that an increasingly wide ecosystem of devices is supported in this spectrum. It includes radiomicrophones and wireless headphones but perhaps even more critically, a growing number of Internet of Things (IoT) technologies that are seen by many as being at the centre of the next stages in the development of the Internet. This includes sensors (e.g. thermostats, light sensors), smart meters (electricity, gas and water) and a wide range of smart-city applications such as transport management. Digital UK's proposed plans involve changing the frequencies used by these devices, which is notoriously difficult. How long, for example, do the keyfobs that unlock your car door last - as long as the vehicle itself in most cases. So clearing a short-range device frequency won't be completed until every device in a band has been replaced by a new one.

The report only pays passing comment to the new 600 MHz mobile band that is being implemented in the USA. In fact, the report seems to suggest that even its most conservative re-organisation option would release so much capacity that there would be no need for the 600 MHz band:
...even the more modest increase of 25% in Option 1 would be similar to the capacity that could be provided by repurposing the 600MHz band...

mobile uplink downlinkIt makes this claim as a result of an oddity of current mobile technology, in which the amount of spectrum (and capacity) that is available to a mobile user is roughly equally split in the uplink and downlink directions (e.g. to the network from the user, and from the network to the user respectively). If the band was re-purposed as Time Division Duplex (TDD), the share of uplink and downlink capacity can be changed, and the report assumes that 80% of overall capacity would be made available for downlink and 20% for uplink (this is in fact in line with current estimates of the real split of usage). If this is the crux of the argument, then doing nothing at all to actually change the overall amount of mobile capacity available, but changing all of the existing allocations to TDD would approximately yield a 60% 'improvement' in downlink capacity, but this would be to the loss of uplink capacity which would fall by 250%! There is no gain without pain. In addition, TDD operators in adjacent mobile spectrum need to fully synchronise their networks otherwise there needs to be a guard-band between them, reducing the overall efficiency of use and opening up new gaps.

Whilst the report makes a valid argument about whether the future of mobile should be TDD or FDD, it is perhaps no surprise that it chooses this solution to theorise about an improvement in the efficiency of use of UHF spectrum, over and above the use of the new 600 MHz band, whose use would obviously entail the loss of (yet) more spectrum for digital terrestrial television. Sadly for Digital UK, the required pain, in terms of re-organising existing mobile networks, and replacing all short-range devices is sadly never going to counterbalance the gain of a few extra MHz of UHF spectrum.
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