Wireless Waffle - A whole spectrum of radio related rubbish
Nuff sed...?signal strength
Friday 27 February, 2015, 15:09 - Spectrum Management, Much Ado About Nothing
Posted by Administrator
Experts at the University of Surrey have allegedly achieved wireless data transfer speeds of 1Tbps (Terabits per second), albeit in laboratory conditions and over a distance of just 100 metres. Sizzle! Then again, just imagine the cost of rolling out the 10 million or so cell sites that would be needed to cover the UK. Ow! Nonetheless this is a significant achievement. Yay!

1tbps zoom zoom

Mobile data connections working this fast would be able to transfer the contents of a blu-ray disk (typically 50 GigaBytes) in just under half a second. Wow! At typical current average mobile internet tariffs, the cost of transferring the data for the blu-ray would be around GBP200. Wowzer! Assuming you wanted to do this every day, the monthly cost of your mobile contract would be around GBP6000. Zowee!

Do we really need to say any more?
add comment ( 119 views )   |  0 trackbacks   |  permalink   |   ( 2.8 / 905 )

DAB Dead Line?signal strength
Friday 30 January, 2015, 14:48 - Broadcasting, Licensed
Posted by Administrator
ofcom logo 1Yesterday was the final day for applications to Ofcom for a new national digital radio (DAB) multiplex licence. The licence was first advertised on 1 July 2014 with a deadline for submissions of 31 October. The deadline was then extended to 29 January to, according to a516digital, "allow a prospective licence applicant sufficient time to obtain information from Arqiva, which owns many DAB transmitter sites."

Two companies have applied for the licence:
  • Listen2Digital: A joint application from Babcock Media Services and Orion Media, a commercial radio group. Babcock Media run the transmitter network for BBC World Service.
  • Sound Digital: A consortium of Arqiva, a transmission company, and commercial radio broadcasters Bauer and UTV Media GB. Arqiva is the monopoly who run the existing UK digital TV, DAB and the majority of FM transmitters.

This year will mark the 20th birthday of DAB radio. According to Ofcom's latest digital radio market report:
...over the full 12 months to June 2014, digital listening (including DAB, DTV and online) accounted for a 36.3% share of all radio listening hours.

Note that this includes listening on digital television (DTV) and online via the web. The same report also states that:
Two-thirds of digital radio listening is through a DAB set.

Taking both of these into account, the report shows that DAB accounts for just under 24% of all radio listening hours. Of the digital-only stations, only 5 have audiences of over 1 million listeners.

Station Audience Audio Quality
BBC 6 Music 1,855,000 128 kbps, stereo
BBC Radio 4 Extra 1,654,000 80 kbps, mono
Absolute 80s 1,168,000 64 kbps, mono
1Xtra from the BBC 1,099,000 128 kbps, stereo
Radio 5 live sports extra 1,039,000 64 kbps, mono

For comparison Absolute Radio reach 1 million listeners in London alone, using one FM station and not a network of dozens of national (and expensive) digital transmitters. Capital Radio, BBC Radio 2 and BBC Radio 4 all have over 2 million listeners in London. The cost per listnener, therefore, for digital services is far, far higher than for older technologies which is in part, forcing the quality of the services down (and into mono). That being said, these digital-only stations have larger audiences than any station outside London (Free Radio in Birmingham, arguably the largest station outside London, reaches around 380,000 listeners).

As is clear from the table above, many services, even the popular ones, are in mono on DAB (though in stereo on-line and on DTV) and use very low bit-rates (remember that these are encoded in mp2 not the more common and higher quality mp3). The low bit-rates and mono signals mean that many of the services sound dull and lifeless compared to their analogue, FM, competitors.

Though Ofcom paint an upbeat picture, in particular citing that digital radio listening has increased by 2.4% over a 12 month period, this hides the fact that digital's share of listening has stagnated over the past year (it was 36.8% in the second quarter of 2013 and exactly the same in the second quarter of 2014).

dab technologyThe new national digital radio licensee, once on-air, will be able to run DAB+ on their multiplex which will at least offer the use of mp4 audio encoding and hopefully, therefore, better quality audio (though it does not stop them using even lower bit-rate mono). The bigger question has to be whether there is really a business case for digital services. The cost of transmission is high, listenership is low (and not growing significantly) and the quality is poor. Which is exactly why medium-wave broadcasting is dying a death.

Ofcom has set criteria that will determine when the time is right to switch-off analogue transmitters and go fully digital. It requires that 90% of the UK has a digital signal and that 50% of listening is on digital radio. With digital radio listening stuck below 40% and no real signs of growth, it looks as if these criteria will never be met. Of course if you applied the same criteria to FM broadcasting, we would be switching off digital radio today.

dabradioUnless something fundamental changes, it's difficult to see how DAB is going to suddenly become the default method of listening to radio. Even listening via the Internet (using apps such as TuneIn) will be unlikely to become the default method of listening to radio given the simplicity and low price of FM radios (and the fact that listening on FM does not use any of your monthly mobile data allowance). The only way this could happen is if there is a ban on the sale of FM radios. It would, however, be political suicide for any regulator to enforce such a ban as both broadcasters and listeners would no doubt complain very vociferously.

So what is the future of DAB? Does it have one at all? Or is it time to set a DAB 'dead-line' and turn it off? Your views and thoughts very welcome!
1 comment ( 153 views )   |  0 trackbacks   |  permalink   |   ( 3 / 1081 )

Martian radio amateurs appeal spectrum allocation decisionsignal strength
Thursday 22 January, 2015, 10:48 - Amateur Radio, Broadcasting, Licensed, Radio Randomness, Spectrum Management
Posted by Administrator
Radio amateurs with designs on operating from the planet Mars are appealing against a decision by the Consultative Committee for Space Data Systems (CCSDS) to allocate the 70 cm amateur band (430 - 440 MHz +/-) for communications between satellites in orbit around the red planet and the numerous rovers that criss-cross its surface.

In a statement, released by the Mars United People for Planetary and Earth Transmissions (MUPPETs), tea-drinking general secretary Arthur Dent said,
MUPPETs have been planning a DX-pedition to Mars for some time. To discover that our officially allocated radio frequencies are already in use is just not fair. It constrains our ability to talk about radio stuff to each other and means other radio amateurs around the solar-system will be denied extra points in the forthcoming 'talking about radio stuff with other radio nuts' contest.

Responding to the accusations, Prostetnic Vogon Jeltz of the CCSDS commented,
prostetnic jeltzThe 70cm frequency band has been used for communications on and off Mars since the Viking lander first set foot on the planet back in 1976. The MUPPETs have had plenty of time to comment. The plans for frequency use on Mars have been available at the local planning office on Alpha Century for fifty of your Earth years, so they've had plenty of time to lodge any formal complaints and it's far too late to start making a fuss about it now. I'm sorry but if they can't be bothered to take an interest in local affairs that's their own regard.

Appallingly obvious references to the Hitch-Hikers Guide to the Galaxy aside, it may surprise many people to learn that there is, indeed, a frequency plan for Mars. And that there are already 5 communication satellites in orbit around the planet! For communication from the rovers on the surface to the orbiting satellites, frequencies in the range 390 to 405 MHz are used. For the link down from the orbiters to the rovers, the frequency range 435 - 450 MHz is used, which falls inside the amateur radio 70cm band.

The choice of the particular frequencies in use (on Mars) is designed to try and stop anyone deliberately causing interference from the Earth, whilst retaining ease of use on Mars (i.e. the ability to use omni-directional antennas). The various satellites orbiting Mars typically get no nearer than around 400 km from the surface and communication with rovers typically takes place when the satellites make their closest pass. The shortest distance between the Earth and Mars is typically around 60 million km. The table below shows the path-loss at 415 MHz of these distances.

Route Distance Path Loss
Satellite to Mars surface 400 km 137 dB
Earth to Mars 60,000,000 km 240 dB

So the difference in path loss is just over 100 dB. For a transmitter to cause interference from the Earth to communication on Mars, it would therefore have to have a radiated transmitter power 100 dB higher than the signals passing between the rovers and the satellites.

mars uhfA very good description of the communications with Mars is provided by Steven Gordon (from whom the diagram on the left is shamelessly plagiarised). The transmitter power used on Mars is 5 Watts (7 dBW), so in order to cause interference from Earth, a transmitter power of around 107 dBW, or 50,000,000,000 Watts (a.k.a. 50 GigaWatts) would be required. Would it be possible to generate such a signal?

Firstly, it ought to be possible to generate at least 100,000 Watts (100 kiloWatts or 50 dBW) of power at the necessary frequencies as television transmitters for the UHF band that reach this level are available. So what is then required is an antenna with a gain of 57 dB. This requires a dish with a diameter of around 150 metres. The largest dish antenna in the world is the radio telescope at Arecibo, Puerto Rico, which is 305 metres in diameter.

muppets cq dxIf a high powered television transmitter was therefore connected up to the Arecibo radio telescope antenna, it ought to be more than possible to jam the transmissions between the Mars rovers and the orbiting satellites during periods where the Earth and Mars were closely aligned. Of course this kind of power level is way beyond the normal licensing conditions of a typical radio amateur and the right conditions would occur roughly every 2 to 3 years when the Earth and Mars come closer together. Nonetheless, commenting on this finding, Arthur Dent of the MUPPETs jeered,
Safe from interference, eh? Who looks silly now then Jeltz!

add comment ( 76 views )   |  0 trackbacks   |  permalink   |   ( 2.9 / 1106 )

Ofcom proposes closure of stable doorsignal strength
Monday 19 January, 2015, 16:25 - Radio Randomness, Spectrum Management
Posted by Administrator
comtrend pltOn several past occasions, dating back to 2008, Wireless Waffle has reported on how several users of the short wave spectrum including radio amateurs, broadcasters, air traffic controllers and NATO, have raised concerns about interference caused by power-line telecommunications (PLT) devices (such as the Comtrend unit pictured on the right). PLT devices allow the use of home electrical wiring to carry computer data by injecting radio signals over the wires. As electrical wiring is designed to carry signals with a frequency of 50 Hz and not 5 MHz, the injected radio signals have a tendency to leak out everywhere and cause radio interference over a wide area.

Groups such as UKQRM and Ban PLT have long campaigned that PLT devices (also known as Power Line Adapters) should be taken off the market as they do not comply with the relevant emissions standards.

Over all of this period, the UK spectrum regulator Ofcom, has staunchly refused to accept that these devices contravene any regulations, though they have taken action in a number of cases where the interference they cause has exceeded even their expectations. Over the same timeframe, a number of other devices have also been found to cause high levels of radio interference, particularly cheap electrical devices, often imported on the grey market from China. These include things such as laptop power supplies, LED lighting and solar panel electrical controllers. Yet Ofcom continued to refuse to accept that anything needed doing.

It is therefore somewhat of a bolt from the blue that on January 15th, Ofcom released a consultation document, entitled 'Notice of proposals to make The Wireless Telegraphy (Control of Interference from Apparatus) Regulations 2015' in which it wishes to implement new controls over these devices by making it a criminal offence to operate them if they are causing interference to wireless telegraphy (e.g. radio services). Part of this seems to be driven by the fact that Ofcom were unable to deal with many interference complaints under existing regulations and that this could be regarded as a potential safety-of-life threat where the interference was caused to, for example, aeronautical services.

According to the consultation paper, there were 114 cases of interference reported in 2014, 'where undue interference was caused ... and capable of resolution'. Of those 114 cases, only 3 could be cured quickly using existing legislation and in the other cases it required voluntary action by the user of the equipment to bring about a solution. Under the proposed changes, all of these cases could be dealt with by law, meaning that instead of volunteering to fix the problem, users could be prosecuted if they didn't.

devil slop 2The big question has to be whether such a change would make any difference. Would those selling the devices stop doing so? Presumably not, as there is no law against selling them, just using them. Would they warn buyers of the new law? Not if it damaged sales. And what will happen if Ofcom threaten prosecution to someone who believes they have been using equipment quite legally, having purchased it legitimately, and having seen the various markings on the box that said it complied with the necessary standards? Will Ofcom then look silly for allowing such devices to have been sold in the first place? Sadly, the UK legislation on such things is still somewhat muddy. It is possible to sell, for example, FM transmitters, mobile signal boosters and even GPS jammers. It is just not legal to plug them in and use them.

ofcom horse boltingBan PLT are recommending that as many people as possible respond to the consultation, encouraging the changes to be implemented. No doubt organisations which manufacture or sell the devices will be arguing against the changes and so it is important that those who use the radio spectrum, especially the short wave spectrum, respond to show the strength of feeling.

There is an old saying in England, 'closing the barn door after the horse has bolted'. Effectively it means trying to solve a problem, after it has happened. The new powers proposed by Ofcom may have some effect in allowing Ofcom to convince users to turn off whichever device it is that is causing the problem, but it is by no means certain that the threat of 'turn it off or we will sue' is going to win anyone any friends, Ofcom, suppliers, BT and radio listeners alike.
add comment ( 45 views )   |  0 trackbacks   |  permalink   |   ( 3.1 / 957 )


| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Next> Last>>