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Why change from analogue to digital broadcasting
And what is this digital dividend anyway? (With apologies to Bob Pease)

This short article questions why the world is changing from analogue to digital TV broadcasting and goes on to explain the term 'digital dividend' which is used by governments and agencies to quantify the benefits of changing.

August 2010

Why make the change from analogue to digital?

I have heard and read of some odd reasons for doing this. Most of them are meant to sound altruistic. That is to say reasons given will infer there is a benefit to the consumer. As with most things, there are part-truths and a lot of nonsense spoken along the way.

The oddest reason I read of was that parts to make analogue products; TV sets, transmitters etc will become hard to obtain. This is an absolute nonsense. Believe me, the parts used to build analogue TV's, DVD recorders and analogue transmitters have 90% in common with their digital counterparts. There is no way we have suddenly forgotten how to make analogue equipment.

Reason no.2: It is becoming more expensive to build analogue products.
Well, you can argue that this is true, but it is true only after there has been an established trend away from making analogue things. Manufacturers have reduced or stopped their analogue production lines in favour of digital and this has been happening now for the past 10 years or so. This groundswell to digital in the manufacturing sector does mean that it is now a more expensive proposition to reverse the situation and recommence building analogue products. But this is not 'the reason' that we need to go digital, it is simply an outcome from the trend that has occurred already. If there was a will to do so, those analogue production lines could be re-established and aside from an initial start cost, analogue products could be built for the same money that they used to be built for. It is unlikely we would go back, nor am I suggesting that we do so, but the point is that manufacturing costs were never the reason for commencing a path away from analogue broadcasting.

Reason No.3: You get more channels.
You do, but who asked for that and who benefits from it? Not the broadcasters. FTA broadcasters are currently simulcasting. That is, they have to broadcast their existing programmes on analogue AND digital platforms. This situation in New Zealand has been with us for 3 years already and will continue for 3 to 5 years more. Double transmission costs for broadcasters and no extra income. Only when Analogue is switched off will the broadcasters costs for transmission reduce. What about all these extra channels? The broadcasters don't want this either. It costs more to run these extra channels and their income streams don't keep up with the additional costs. TVNZ currently have two digital-only services called TVNZ 6 and TVNZ 7. The costs of these two are largely borne by the government because TVNZ couldnt otherwise afford it. MediaWorks have two digital-only services called TV3+1 and C42. The TV3+1 service is just a copy of TV3 running an hour later and is dirt cheap apart from transmission costs. C42 is a jukebox music channel indistinguishable from the existing C4 and with minimal setup costs. Kordia run the 3rd multiplex on the Freeview N.Z DVB-T platform and this does offer some minority interest programming such as Parliament TV and Chinese channels; things which could not happen under analogue.
What about the viewer? Do these extra programmes benefit the viewer? Always going to be arguable but how many hours can you spend TV watching.

Reason No.4: Better quality on digital
This also is a part truth. Digital terrestrial TV removes reception problems. Viewers who didn't live in the best analogue reception zones used to get a variety of picture defects such as snow, ghosts, interference lines and so on. With digital, these don't exist. Instead, you get..... no reception. Or, perfect reception. Those same analogue reception problems are still present, but, with digital transmissions, they don't determine your picture quality, just whether you get any reception at all. Digital terrestrial transmissions can have high-definition. Not all digital transmissions are HD; in fact only a very few at the moment. HD is used as a sweetener to promote digital over analogue, but the truth is that the system cannot support all channels in HD and those that are not in HD are the same quality that you used to get in analogue, if you had good reception. Even HD doesn't mean perfect quality. I must admit I am aggrieved by seeing the term 'crystal-clear' being parroted by all and sundry, when advertising digital TV and digital TV products. Some of the programme quality out there now is so poor, they must be using a very cloudy crystal.

Reason No.5: Reduced radio spectrum occupancy for digital TV.
This one is certainly true and the rest of this article explains this further. This is what the government refers to as the 'digital dividend'. Governments all over the world 'own' the entire radio spectrum in their country and they lease bits of it to anyone who wants to pay for it. However, this is a consequence of going to digital TV and not the reason for wanting to change in the first place.

And the real reason for changing from analogue to digital broadcasting? The whole impetus came from the manufacturing sector. They realised people already had their TV's, their VCR's and DVD players. Products generally lasted for years and sales were reducing rapidly. They needed 'new' products to make and sell, which of course made existing appliances obselete. That was where the push came from and it worked. Digital TV is now a fait-accompli. Along with it, the manufacturers sell you blu-ray, set-top boxes, PVR's, and HDMI cables at exorbitant prices and now look, they are hitting us with 3D. All good for the makers of products and not good for the users; you and me.

What is the digital dividend

This term refers to the economic benefit to the country when analogue TV is finally turned off. The reason that there is an economic benefit relates almost entirely to the fact that it takes less of the radio spectrum to broadcast digital TV than it does to broadcast analogue TV. Governments can then lease the freed-up spectrum to other parties and charge them fees, of course.

A look at the before and after radio spectrum for TV broadcasting

The following diagram depicts the existing spectrum used for TV at the top and what will be used for TV after the analogue TV services are switched off at the bottom.

spectrum diagram

At the present time, broadcast TV takes up 77MHz (11 x 7MHz channels) in the VHF bands plus 296MHz (37 x 8MHz channels)in the UHF band. [The UHF band in New Zealand is already less than that used internationally]
So, current total spectrum occupancy is 373MHz. After analogue is switched off, there will be no TV in the VHF bands and the UHF band will be limited to 23 x 8MHz channels for a total occupancy of 184MHz.
At the present time, there is very little interest for the soon to be vacant VHF spectrum, but the top part of the UHF band above 694MHz is prime real estate for the telcos who want it for 4G mobile use. They will pay millions to the government in order to lease that spectrum. That rake-off is much of what the government calls the 'digital dividend'. Analysts who are much cleverer than me have estimated huge benefits to the country as a whole but interestingly, that economic benefit is larger if the analogue services are turned off sooner; say in 2013.
If nobody wants the VHF spectrum, perhaps the VHF analogue TV broadcasts could just as well stay going, although the broadcasters themselves do face increasing costs in maintaining the ageing equipment

What could VHF be used for

There is no doubt that the extra spectrum of 112MHz to become available in the UHF band will be valuable, but so far nobody has expressed much interest in the 77MHz of VHF spectrum that will also become available. In the UK, the part between 174MHz and 230MHz is actually used for DAB (digital audio broadcasting). It is a good band for DAB, but in New Zealand none of the radio broadcasters really want to change to DAB. They are quite happy with FM and are resisting the move to digital. FM is well established, radios are cheap and the radio transmission system is relatively cheap to operate. Why change? Only time will tell if the all pervasive move to digital hits radio too. Other uses might include radio links and fixed to mobile telecommunications.

Power savings?

I have seen it written that another benefit of the digital dividend is that less electricity will be needed to be generated once all analogue transmitters are turned off. On the surface, it sounds good because all those high power TV transmitters operated by TV1,2,3 and 4 do use a lot of electricity. However a calculation shows that the savings are miniscule in the overall scheme of things.

I made calculations like this:
Current New Zealand TV transmitter stations can be categorised into high, medium and low power classes. The high power stations use transmitters from 5kW to 20kW RF power. Analogue TV transmitters of this power are about 25% efficient and there are 8 sites using transmitters of this power. Similarly there are 32 medium power sites using transmitters 1000 watts to 5000 watts. Low power sites use equipment under 1000 watts. Some TVNZ stations are only 20 milliwatts. Currently there are 260 TV sites in this low power category.
Then, from the site data I have added the transmitters for TV1, TV2, TV3, C4, MaoriTV and Prime and totalled the AC consumed based on the known efficiencies of each power class. I know these because I have measured many of them, but the total is an average.

The total AC power consumption of all operating analogue TV transmitters is close to 2.6MVA. By contrast, the current DVB-T system, using mainly 1kW transmitters uses about 135kVA total across the country. If the DVB-T system expands to 87% of the population, the power consumed in total will become about 195kVA. Less than 1/10th of that used for analogue.

These numbers are large in terms of individual domestic users like you and me, but are small bikkies in industry. The broadcasters will however, benefit to the tune of about NZ$3.3 million dollars per annum in power cost savings once analogue is turned off, but what does it mean for the country as a whole?

TV transmitters operate 24 hrs a day. All those analogue transmitters use about 23GWh of electricity per annum. After they get switched off the DVB-T network will use about 1.7GWh per annum. So the saving to the country is about 21GWh p.a. I have ignored transmission components other than transmitters because they are a very small part of the total power consumed. According to the M.E.D, New Zealand consumed 40,000GWh of power in 2007 across all sectors. The amount of electricity used by the entire analogue TV transmission system is 0.06% of that. An electronics engineer would say 'that will be lost in the noise' but in plain language, it is utterly insignificant and could not be measured as a saving.


But wait, as they say, there's more.

To receive digital broadcasts, people need to buy either a set-top box, a personal video recorder (PVR) or a TV with integrated Freeview. People who watch satellite cannot buy an integrated TV so they must have one of the other options. Only 75% of the country has terrestrial digital coverage now and that may increase to 87%. Therefore, at least 13% of the population will have to be on satellite, and many more are using Freeview satellite by choice. SKY satellite users also have a set-top box but assuming SKY penetration does not increase markedly from present, then they become neutral in any additional household usage from this point forward. Set top boxes use power and that power is, in a lot of cases, additional to whatever power the household uses currently for TV watching.

A ordinary DVBT set top box uses about 15VA of power.
A PVR uses about 40VA.
For the sake of argument, let us assume that 50% of Freeview terrestrial households buy an IDTV and lose their existing CRT television. This might be optimistic because some will consign the old TV to the office or bedroom and buy another STB to run that. Replacing a 29" CRT with a 32" LCD IDTV means nil change (broadly speaking) in power consumption. However, 50% or 1.2 million households are now going to require more power and as a starting point, let us use 20VA per household. (I use VA and not true watts because the VA figure is what the country has to generate) The conservative increase nationally then, is 24MVA and the more likely increase is 50MVA folks. Assuming you turn off your set top boxes and put them on standby for 16 hours a day, you will reduce the consumption by ...not much. Some set top boxes do not reduce their power drain at all when on standby. PVR's on standby might use half the power, but these products may not ever be put in standby if they are set to record something in the early hours for example. The upshot of all this is the country domestic power consumption will INCREASE due to analogue switch-off. As an estimate that will be an annual increase of 200GWh at least. Could be double that, especially as people trade in their old TV's for much larger ones which, yes, use even more power.

So, the national power savings that accrue by replacing the old analogue transmitter network are FAR outweighed by the increase in power consumption incurred by the public having to buy new digital receivers to get their shiny, crystal-clear digital TV service.

Note: A future article will explain why digital TV uses less spectrum space than analogue.


Axino-tech Consulting & Services , August 2010.