Wireless Waffle - A whole spectrum of radio related rubbish
Is it time for a 'Digital Switch-Off'?signal strength
Wednesday 21 May, 2014, 20:02 - Broadcasting, Spectrum Management
Posted by Administrator
poor cousinIt could be argued that before the switch-over from analogue to digital television broadcasting, the value of terrestrial broadcasting was on the decline. Faced with fierce competition from cable and satellite, each offering 10 or more times the number of programmes, terrestrial television was a poor cousin whose main use was often to deliver public service broadcasting and, through general interest obligations imposed by national governments, to provide an accessible (free-to-air) service to 95% or more of a country's population (measured both geographically and demographically).

As digital switch-over has taken hold, terrestrial broadcasting has had a repreive and is now able to offer true multi-channel television. Where previously it was only possible to broadcast a single television station on a single frequency, that frequency can now hold 10 or more standard definition (SD) channels, or 4 or 5 HD channels. Where there may have been 6 analogue stations on air, there can now be upwards of 60 stations. In many cases, 60 stations is enough for the average viewer and the bouquets of channels offered on cable or satellite may now begin to seem expensive compared to free-to-air DTT. In many countries the draw of cable and satellite TV is no longer the sheer variety of channels available, but the premium content that is on offer. Pay-TV services offering sport and movies continue to be popular, but such premium content is not usually available on DTT. Nonetheless, for many viewers DTT is perfectly sufficient.

biting at the heelsBut just as digital terrestrial TV (DTT) has had a new lease of life, the other broadcasting platforms are once again biting at its heels with new service offerings. Whilst 3D television seems to have taken a back seat for the time being, new, even higher definition television, is stepping to the fore. Ultra-High Definition (UHD) has twice the resolution of standard HD and large UHD televisions are already on show and on sale in many retailers. At present there is minimal UHD content, however a hand full of new UHD channels are being launched and, for example, the World Cup football in Brazil will be broadcast in UHD.

To be able to see the difference that UHD makes compared to standard HD, a very large television set is needed (42 inches or greater) and it could therefore be argued that UHD will always be a niche product. Then again, many broadcasters believed that HD would be a niche, but it is becoming the de facto standard and average television sizes are on the increase.

Technically speaking, UHD requires a bit-rate of around 20 Mbps. Whilst such bit rates are relatively easy for cable and satellite networks to deliver, broadcasting UHD over DTT would require at least half of a DVB-T2 multiplex, and the most advanced video (HEVC) codecs. In practice this means that were a terrestrial frequency currently carries 10 or more SD, or 4 or 5 HD channels, it might, at best, be able to offer 2 UHD channels.


uhd samsung tvBut that is not the end of the story. Just around the corner is super-high vision (SHV), sometimes called 8K, which once again doubles the resolution of the picture compared to UHV. SHV will require around 75 Mbps to be broadcast and at this point, whilst cable and satellite are still in the game, DTT is no longer able to broadcast even a single programme on a single frequency (without very complex transmitter and receiver arrangements that would require, for example, householders to install new, and potentially more than one, antenna). Of course to benefit from SHV, an even larger TV screen will be necessary, but with the growth in home cinema, it is can perhaps be expected that in time, a goodly proportion of homes will want access to material in this super high resolution.

So where does that leave DTT? Arguably, within a few years, it will once again be unable to compete with the sheer girth of the bandwidth pipe that will be provided by cable and satellite networks. It's probably worth noting at this point that most IP-based video services (with the possible exception of those delivered by fiber-to-the-home) will also be unable to deliver live SHV content. This time there will be no reprieve for DTT as it simply does not have the capacity to deliver these higher definition services.

What is therefore to be done with DTT? Is it necessary to provide continued public service, universal access, free-to-air services that were the drivers for the original terrestrial television networks? Is its role to provide increased local content which might be uneconomic to broadcast over wide areas? Should it be used to deliver broadcast content to mobile devices where it has more than sufficient capacity to provide the resolution needed for smaller screens? Or, should it be turned off completely, and the spectrum it occupies be given over to something or someone else?

In countries where cable and satellite penetration is already high, there is arguably nothing much to lose by switching DTT off. In Germany, for example, RTL have already withdrawn from the DTT platform and there is talk of turning off the service completely. In countries that have not yet made the switch-over, it might be more cost effective to make the digital switch-over one that migrates to satellite (and cable where available) than to invest in soon-to-be-obsolete DTT transmitters.

tv service goneBroadcasters should be largely agnostic to the closure of DTT. After all, their business is producing content and as long as it reaches the audiences, they ought not to care what the delivery mechanism is. Other radio spectrum users (e.g. mobile phones, governments) would surely welcome the additional spectrum that would become available. So who loses? Those companies who currently provide and operate the DTT transmitter networks, such as Arqiva in the UK, Teracom in Sweden and Digitenne in the Netherlands, who stand to lose multi-million pound (or Euro) contracts. For these organisations the stakes are high, but even the most humble economist would surely admit that the benefits elsewhere outweigh the costs. So let's turn off DTT - not necessarily today - but isn't it time to plan for a 'digital switch-off' to follow the 'digital switch-over'?
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90 years of the 'time pips'signal strength
Friday 7 February, 2014, 13:43 - Broadcasting, Licensed, Much Ado About Nothing
Posted by Administrator
What a disappointment it was to find a recording called 90 years of the time pips, to discover that it is a special version of the pips¹ designed to celebrate their 90th birthday.

Wouldn't it have been more fun to have calculated how many pips there have been in 90 years and then created audio that just pipped (or beeped continuously) through all 90 years? How many pips would that be?

90 years × 365.25 days × 24 hours = 788,940 hours²

The first 5 pips have a duration of a tenth of a second, and the final pip has a duration of half a second, so the total duration of the pips each hour is exactly 1 second (5 × 0.1 + 0.5). A constant tone of duration 788,940 seconds (which is 9 days, 3 hours and 9 minutes precisely) would therefore represent '90 years of the time pips' much more accurately.

So here for your listening pleasure, is the Wireless Waffle tribute to the pips... 90 years of pips compressed into 9 days, 3 hours and 9 minutes.

play 90 years of the pips
Just click the play button, sit back and enjoy!

gladys knight and the pips¹ Not to be confused with Gladys Knight's backing group who, whilst also played on the BBC from time-to-time, are not the pips in question here.

² Of course the pips have not been broadcast every hour over that period. Other time signals (such as the chimes of Big Ben) are used on some hours. Equally the BBC has not always been a 24 hour service, so this figure is probably a significant over-estimate.
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Local TV test transmissions on-airsignal strength
Wednesday 29 January, 2014, 11:01 - Licensed
Posted by Administrator
It's a surprise that there haven't been more reports of this, but it seems that the Local TV services licensed by Ofcom last year are beginning to come online. The video clip below shows test of one of the two national channels that will be operated by Comux (to try and generate enough profit to run the transmitters) as received in Clacton, Essex. The signal comes from the Crystal Palace transmitter in London.



There doesn't yet seem to be placeholder for London Live which will launch in the capital in March on channel 8 on Freeview, but the two national channels awaiting launch and currently sat on channels 791 and 792 so you can check whether you will be able to receive it (a re-tune may be necessary).

The first of the new raft of local TV stations on the air was Estuary TV in Grimsby, whose transmitter also does a pretty good job of covering nearby Kingston-upon-Hull.

Wireless Waffle previously reported on the lessons to be learnt from the failed attempts at local TV in the UK in the past, and on the uncanny similarity between Comux (the local TV network operator) and Arqiva (who are providing the transmitters to Comux.

There are still a large number of local TV transmitters to be put on-air, so keep checking your set-top-boxes for new channels. Oh, and whilst you're at it, see if you can get the additional Freeview HD multiplexes that have quietly launched around the UK providing such excitement as BBC4 HD and Al Jazeera HD. Why couldn't they have put something useful in HD such as Dave or Film4?

You can check the channel line up on Freeview at your location by using the handy form below.

Your Postcode
House Number or Name
(Providing a house name or number is not essential but makes your results more accurate)

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Wave To Go!signal strength
Monday 27 January, 2014, 15:30 - Broadcasting, Licensed, Spectrum Management
Posted by Administrator
The BBC recently reported that Radio Russia have quietly switched off the majority of their long-wave broadcast transmitters. Whilst the silent passing of Russia's long wave service will not rattle the front pages either in Russia or anywhere else for that matter, it does raise the question of the long-term viability of long-wave broadcasting.

atlantic252During the early 1990s there was a resurgence of interest in long-wave radio in the UK caused by the success of the pop station Atlantic 252. But by later in the decade, the poorer quality of long-wave broadcasting compared to FM, together with the increased proliferation of local FM services in the UK eventually led to the demise of the station. Similar logic appears to have been used by the Russian authorities who now have a much more extensive network of FM transmitters and clearly feel that the expense of operating long-wave is no longer justified.

One of the great advantages of long-wave broadcasting is the large area that can be covered from a single transmitter. For countries whose population is spread over very wide areas, long-wave offers a means to broadcast to them with very few transmitters. Conversely, the large antennas and high transmitter powers required to deliver the service make it an expensive way to reach audiences. Presumably there is a relatively simple equation that describes the cost-benefit of long-wave broadcasting, i.e.:

worthwhileness equation


Where:
W = Worthwhileness of Long-Wave Broadcasting
C = Total cost of providing the service
A = Audience
FM = FM
LW = Long Wave
Tot = Total

As long as W>0 as A(FM) increases it continues to be worthwhile to broadcast on long-wave as the cost of providing the service is greater than the cost of doing the same thing using FM.

The cost of providing an FM service - C(FM) - is not constant, and will increase with the audience served, and not in a linear fashion either. The final few audience will cost significantly more than the first few. This is because stations which only serve small, sparse communities tend to be more costly (per person) than ones serving densely packed areas.

The cost of providing the LW service - C(LW) - however, is largely constant regardless of how many people listen to it.

It's therefore possible to draw a graph of the cost per person - C/A - of the FM audience and the cost per person of the long-wave audience, as the FM audience increases.

long wave fm graph

The figures used in the graph above are illustrative only. They assume that:
  • The cost per person of providing an FM service increases by a factor of 10 between the first and the last person served;
  • The cost per person of providing the long-wave service is initially only a third of that of providing the same service on FM.
Based on these assumptions, it is not until the FM audience reaches almost 90% of the population that the cost per listener of FM is less than that of providing the same service on long-wave. As FM coverage becomes more widespread, it is this factor that is causing many broadcasters to cease long-wave transmissions (the BBC has a plan to end its long-wave service too, though there is no date set for the closure yet).

Of course there are many other factors to take into account, in particular the difference in service quality between FM and long-wave, and the proportion of receivers that have a long-wave function. There are thus other factors that will hasten the end of long-wave as FM coverage increases. The same could largely be said for medium-wave where arguably, the problems of night time interference make it even worse off than long-wave (though more receivers have it).

long waveWireless Waffle reported back in 2006 on the various organisations planning to launch long-wave services, not surprisingly none of them have (yet) come to fruition.

There is, however, one factor in favour of any country maintaining a long-wave service (or even medium-wave for that matter), and it's this: simplicity. It is possible to build a receiver for long-wave (or medium-wave) AM transmissions using nothing more than wire and coal (and a pair of headphones) as was created by prisoners of war.
Prisoners of war during WWII had to improvise from whatever bits of junk they could scrounge in order to build a radio. One type of detector used a small piece of coke, which was a derivative of coal often used in heating stoves, about the size of a pea.

After much adjusting of the point of contact on the coke and the tension of the wire, some strong stations would have been received.

If the POW was lucky enough to scrounge a variable capacitor, the set could possibly receive more frequencies.

In the event (God forbid) of a national emergency that took electricity (such as a massive solar flare), it would still be possible for governments to communicate with their citizens using simple broadcasting techniques and for citizens to receive them using simple equipment. Not so with digital broadcasting! Ironically, most long-wave transmitters use valves which are much less prone to damage from solar flares than transistors.

So whilst long-wave services are on the way out in Russia and elsewhere, it will be interesting to see whether the transmitting equipment is completely dismantled at all sites, or whether some remain for times of emergency. Of course if every long-wave transmitter is eventually turned off, there is some interesting radio spectrum available that could be re-used for something else... offers on a postcard!
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