Wireless Waffle - A whole spectrum of radio related rubbish
Adjø FM Radiosignal strength
Tuesday 28 April, 2015, 15:58 - Broadcasting, Licensed, Spectrum Management
Posted by Administrator
norway wave goodbyeThe Norwegian Communications Authority (NKOM) recently announced that FM radio is to be closed-down in Norway by the end of 2017. The closure will begin at the north of the country, and spread southwards. National broadcaster NRK will wave goodbye to FM radio first, followed by major commercial broadcasters. Some smaller, local broadcasters, will be allowed to continue broadcasting on FM but the rest will continue only on DAB or on other digital platforms (such as television or online).

The switch-over in Norway, follows a similar logic as that used by Ofcom in the UK (as previously discussed by Wireless Waffle). There are a number of specific criteria that the Norwegian government said had to be met for the switch-off to occur:
  • NRK's digital services have to have the same coverage as their FM service, and national commercial services need to cover 90% of the country.
  • There has to be an affordable solution for listening in cars.
  • At least 50% of listeners have to be listening to digital radio every day.
The regulator claims that these targets have been met but broadcaster claim that they haven't. The Norwegian Local Radio Association claims that only 19% of listeners use DAB and that other 'digital' listening is through other platforms. They also argue that an 'all digital Norway' would mean that any tourists driving from a neighbouring country who don't have a DAB radio would be unable to receive local traffic and weather information and that this could prove dangerous. Of course, if those tourists hired a car in Norway, presumably this problem would not occur.

radio snowBroadcasters also fear that driving people away from FM onto, for example, online radio would open up a much wider world of competition from the likes of Spotify. In this respect, FM radio represents a way of limiting listener choice and reducing competition so it is perhaps no wonder that broadcasters are keen to ensure the longevity of the medium.

Norway was one of the first countries to complete the switch from analogue to digital television and is no doubt hoping that it's bold decision to close FM radio will give it similar kudos. However there were good reasons for a digital television switch-over, including the greater choice and higher quality recption that digital offered and, perhaps most importantly from the perspective of the regulator and government, the ability to free up some radio spectrum which could then be sold of to mobile operators for lots of money. Wireless Waffle estimates that the sale of the digital dividend spectrum in the auction that took place in 2013 raised around GBP75 million, which is not that much compared to the very large prices paid in other countries.

nkom trailblazingThe FM band is a different proposition though, because other than for radio broadcasting, there are no other (harmonised) uses for the band. It could be used for mobile radio (e.g. walkie talkies) but there aren't any available that operate in that frequency range. It could be used to extend the aeronautical band (which begins at 108 MHz). It could be used for some, as yet uninvented wireless service. But unless neighbouring countries (and the local FM broadcasters in Norway who continue to use the band) also switch off their transmitters, the levels of interference from these stations would be too high to make the spectrum of any real value.

So what is the real benefit of switching to digital? For Norway, perhaps, a chance to be a trailblazer. For any other country, perhaps none at all.
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Polar Foil - virtually not antennas at all?signal strength
Wednesday 1 April, 2015, 11:01 - Spectrum Management
Posted by Administrator
It is almost a law of physics, that the best way to increase the coverage of a transmitter is not simply to turn up the power, but better still to increase the height of the transmitting antenna. Wireless Waffle has discussed the relationship between height, power and coverage before. It is, however, almost a law of nature, that increasing the height of an antenna through building a taller mast will incur the wrath of residents and environmental protestors and as such, there is a political limit to just how high antennas can be mounted.

birds antennaWouldn't it be great if someone invented invisible, or nearly invisible antennas? One option might be to use atom thin superconducting graphene tubes that were self-supporting but so thin as to be virtually invisible. The only downside of such an antenna would be that any bird that flew into it would be immediately sliced in two as the antenna would have almost infinitely sharp edges.

Another option could be to use multiple beams to project and focus energy at a specific point to materialise a virtual antenna. If force (thrust) can be generated by electromagnetic waves in an EmDrive, then could a similar principal be used to project an antenna at a point away from the source of the physical beams? This far-fetched idea is being considered by Professor Nisan Sakasi at the Communications and Spectrum Management Research Centre at the University of Bilkent, in Turkey.

By focussing very narrow microwave beams which cross in a specific quadrifilar pattern, the air atoms at that point can be ionised to become electrically conductive and with careful tuning,quadrifilar radiation can project a virtual antenna at a point separated from the microwave transmitters by several metres. Professor Sakasi has called the antennas 'polar foil', because the area where the virtual antenna is formed, if viewed from polar angles, glints a little like aluminium foil. Of course at night they are completely invisible.

The difficulty for the team at Bilkent is now to find a way of feeding the polar foil with RF energy so that it can actually radiate useful signals. The team believe that with the right beamforming, a 'virtual feeder' could also be created permitting injection of RF signals from a lower point. A secondary problem is that the amount of electricity needed to feed the microwave transmitters which generate the polar foil is 'in the region of kiloWatts', meaning that the power required to form the virtual antennas is currently far more than that required to generate the radio signals that would feed into them.

The advantages of such a system is that, with tighter beamforming, it may be possible to generate the polar foil not just metres away from the microwave transmitters but tens of metres away. As such, antennas could be virtualised far above the ground, without the need to build masts at all. The fact that the antennas are virtual, and not real, means that problems like slicing a bird in half as it flies into the antenna are virtually unreal and thus no damage would be caused.

A spokesperson for the Royal Society for the Protection of Birds, told Wireless Waffle that:
We are very concerned about the idea of superconducting graphene antennas being erected across the country, however we think that many birds would like the idea of a network of virtual feeders!

polar foil beams
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How Not To Install A Satellite Dish (Part I)signal strength
Tuesday 31 March, 2015, 04:51 - Radio Randomness, Satellites, Much Ado About Nothing
Posted by Administrator
It's been a long while since anyone at Wireless Waffle installed any satellite dishes, however as part of a project to improve language skills, it was decided that the WW HQ would be fitted with the kit needed to receive German television. This is the sad story of the trials and tribulations of what should have been a simple job in the hope that it may help others trying the same thing not to fall into the same traps that befell our attempts!

Firstly, a visit to Lyngsat and a browse through the dozens of satellites that cover Europe quickly yielded the fact that the channels that were wanted could be found on various Astra 1 satellites at an orbital position of 19.2 degrees East (19.2E). As a ready reckoner, the following orbital positions are the 'hot-slots' for various European languages:
  • English - 28.2E
  • French - 5W
  • German - 19.2E
  • Italian - 5W or 13E
  • Polish - 13E

astra 1m footprintThe next thing to do is find out what size of dish is needed to receive the satellite that's of interest. This is more complex as it requires a knowledge of the satellite's footprint and the strength of signal at a particular location. For 19.2E in the UK, even a 55cm dish should be fine pretty much everywhere, so a Triax 54cm dish was duly purchased together with a suitable wall bracket and an Inverto LNB.

The mounting of the dish on the wall was relatively straightforward, having made sure that there were no obstructions in the line-of-sight from the dish to the satellite (such as trees or other buildings). With the dish on the wall, the next step is to align it so that it is pointing at the satellite. In general a rough idea of the right direction can be gathered if you know your latitude and longitude and the satellite you wish to receive through many online tools (such as dishpointer.com).

Getting the dish pointing in roughly the right direction is not too difficult, but even a small dish needs to be pointing with an accuracy of better than plus or minus 1 degree (bigger dishes have to be even more accurately aligned) and so some form of fine tuning is needed.

In analogue days gone past, by far the best way to align a dish was to connect it to a satellite receiver, and connect the satellite receiver to a television, and put the whole lot in a place where the TV could be seen from the dish. With the satellite receiver tuned to a channel on the appropriate satellite, it was then just a matter of moving the dish about until a signal could be seen on the TV. Once the signal was found, gently moving the dish from side-to-side and up-and-down to a point where the quality of the picture was maximised was all that was needed. Of course the same method can still be used today, but there has to be a less crude way, right? Right...

slx satfinderThe SLX Satellite Finder costs less than a few metres of CT-100 coax, and provides both a visual indication of signal strength (using the in-built meter) and an audible indication (using the in-built buzzer). All that is then required to use this to align a dish is a 'patch lead' so that the dish can be connected to a socket on the meter and then a lead coming from the (indoor) satellite receiver connected to the other socket on the meter to supply power. So far, so good.

Now, turn on the satellite receiver and return to the dish. In theory, the meter should only register a signal if the dish is pointing at a satellite. However, the modern Inverto LNB was obviously doing a far better job of receiving than the systems that the crusty SLX meter was being designed to work with resulting in a full-scale meter deflection (and an annoying beep that could not be turned off) almost regardless of the position of the dish. No amount of experimentation yielded anything other than full-strength or nothing, and the full-strength indication happened across a wide arc of the sky and with the elevation angle of the dish anything within 10 degrees of that which should have been right. In a word, beeping useless!

sf 95dr satfinderNot to be defeated, and rather than cart the TV and receiver outdoors, a second, seemingly more modern meter was purchased, the SF-95DR Satellite Finder. This proved to be marginally better, but having the dish within 'a few' degrees of the right position still yielded a full-scale signal. At least the beep could be turned off.

An old trick from the analogue days to reduce the signal to make fine tuning the position of the dish easier if the signal was very strong, was to cover the dish in a damp tea-towel. The water in the towel will attenuate the signal making the signal weaker and thus the dish easier to align. This trick was tried using the SF-95DR but alas, only resulted in the need to keep picking up a damp tea-towel from the floor, every time the wind blew it off.

Eventually, more through luck than skill, a point was found where the meter indicated a peak that was within a degree or so of nothingness in nearby directions, suggesting that the dish was aligned to a satellite. An excited scan of the receiver revealed some signals but alas, from the wrong satellite (13 East instead of 19.2 East). Of course the meter would no more know which satellite it was pointing at than an amoeba would know the difference between a car and a lorry, just that both seem pretty big. More fiddling, and a slightly damper tea-towel and a second 'peak' was found. Another tune of the receiver and 'Allelujah!' channels that were being transmitted from 19.2 East were found. But only from one transponder...

dish alignment girlWhat could this mean? Was it that the dish was roughly aligned but that only the very strongest signal was being received? Was it that the LNB was faulty? Was there a fault in the cable from the dish to the receiver indoors? Any (or all) of these could be the problem and with nothing more to go on, it seemed that the only way to resolve the issue was to resort to carting the TV and receiver outdoors so that the screen could be seen from the location of the dish. Doing this would mean that the 'signal strength' and 'quality' bars on the receiver's on-screen menu display could be used to point the dish more accurately.

A new patch lead from the dish to the receiver was fitted with F-connectors (thereby ruling out any problem with the coax feeding indoors). Power up... And the receiver is showing 100% signal strength (very good!) but a signal quality of only 60% (OK but not brilliant). No amount of dish repositioning would yield any improvement and still just the one transponder was receiveable. Before giving up and ordering a new LNB, and with an increasing level of suspicion building up, the meter was taken out of line so that the dish was connected directly to the receiver without the meter in circuit.

Hey presto...! Now the receiver was showing 100% signal and 80% quality and, wait for it, all of the transponders on the satellite could be received. A final fine-tune of the dish position and the quality of reception was increased to 90% - not a bad result at all. Moving the TV and receiver back indoors to the other end of the original run of coax and this excellent result was maintained. It seems that the meter may have been overloaded by the signal from the satellite and was somehow distorting the signal (possibly it was generating harmonics or intermodulation products).

So the lessons from this cautionary tale are:
  • Don't use cheap 'satellite finder' meters to help align dishes, they cause more problems than they solve.
  • Stick to the tried and tested methods and just move a TV and receiver to a place where they can be seen from the dish and use the receiver's signal meter for alignment.
  • Damp tea-towels should be used for wiping down surfaces in kitchens and not for the setting-up of sensitive electronic equipment.

At this point you're probably thinking that this is the end of this cautionary tale, but you'd be wrong... there's more to come! Stay tuned to Wireless Waffle for our next extremely uninspiring episode of: HOW NOT TO INSTALL A DISH.
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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?
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