Wireless Waffle - A whole spectrum of radio related rubbish

Spot the Difference!signal strength
Saturday 28 May, 2011, 15:48 - Pirate/Clandestine
Posted by Administrator
Driving around London the other day, there was time to have a good old tune through the FM band to see how the various new community radio stations were getting on and whether Ofcom had had much success in shutting down the myriad of pirates. But the job was much more difficult that usual! The difficulty lies in the fact that many of the community stations sound like pirates, and the pirates that are still on air sound almost professional, at least as professional as the community stations that are slowly replacing them.

rinseTake Rinse FM (now legally broadcasting on 106.8) as a case in point. Now you might not particularly like the wack-a-jaffa, hardbeat, dirty garage or deep-boom gruffty music that they play (at least that's what it sounded like), but since their move to legality, the main thing which seems to have changed is that the presenters are marginally more professional (some of the street slang used before seems to have been tidied up), can read out a proper phone numbers, and can say where listeners are calling in from and give their names. So instead of 'big shout out to the hard-jaffa massive' and 'big up the 607', it's 'but shout out to Doreen of Tooting', and 'big up Dave who's cleanin' the missis's car'. It's lost it's edge a bit. Much the same can be said of Reprezent whose youth-orientated broadcasting sounds much of a muchness.

london pirateOn the other side, it looks like Ofcom has been doing a reasonable job on some of the pirates. There were certainly a lot fewer on the band with many of the smaller stations seemingly off-air (though this could be because it was mid-week). There was only a brief glimpse of Point Blank, whose signals on 90.2 and 103.5/6 were staples for house-heads. A scratchy sound on 90.2 was all there was and 103.5 has been dead for some time now. Passion FM was still audible on both 91.8 and 97.9 MHz. Unknown FM seemed completely absent but there was a strong signal on 89.4 around North London with no RDS and no announcements which was assumed to be them. One new station was Pulse London who were on one of Unknown's old frequencies of 108.0 MHz. Listening to them, it's clear that they have set up as a streaming web radio station and even state on their web-site that they are 'not available through digital or analogue broadcasts' - a common ploy amongst modern-day pirates, so that they can deny knowledge of the FM transmitter and pretend to be totally above board.

The thing is that with pirate stations increasingly claiming to be legit (and probably paying their PPL and PRS dues) they can start to be a bit more daring with phone numbers and names too. The upshot is that they sound much like the legitimate community stations. The fact that both often fill their daytime schedule with pre-recorded non-stop music makes the situation even worse.

As a result, telling what is legit from what is not is getting increasingly difficult.

Surely it's time for Ofcom to hold an amnesty and work with the more established pirates to find a solution. Give them a licence (cf. Rinse) and bring it all under control. The new 'Vibe1076' for Watford is a case in point. It's test transmissions sound just like any other commercial radio station of which the need is rather dubious. But in North London (much the same area) there are three Turkish language pirates (Bizim FM on 101.8, Radyo Umut on 102.8 and DEM Radyo 90 on 104.2). Surely sitting down with the Turkish community and finding a way to give them something they need would have been much better use of the frequency. (The irony of Umut being just 500 kHz away from London Greek Radio is not lost!) Alternatively, perhaps setting up a London-wide DAB multiplex to be shared by pirates might have the double effect of getting them away from their illegal FM transmitters and encouraging sales of DAB radios. Either way, the true 'pirate' sound of London is morphing into a less exciting, homogenous, slightly blandified version of its former self, but perhaps that is the way of progress!
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Bye bye broadcasting, hello mobile donglesignal strength
Tuesday 5 April, 2011, 13:15 - Broadcasting, Licensed, Spectrum Management
Posted by Administrator
squeezeeApparently, mobile phone operators are beginning to run out of capacity on their networks due to all the data traffic that is being generated by smart-phones and people using broadband dongles in their laptops. Of course, whether or not this is true or not today or whether it is just an excuse for poor service quality, there will almost certainly come a time in the relatively near future when it the squeeze on spectrum becomes reality.

A typical mobile operator in an average European country will currently have access to something like 100 MHz of radio spectrum - 50 MHz for the uplink from phones to base stations and another 50 MHz in the opposite direction - more commonly written 2 x 50 MHz. This will be in usually two (or more) of the commonly available mobile bands, such as:
  • 900 MHz (actually 880 - 915 and 925 - 960 MHz)
  • 1800 MHz (1710 - 1785 and 1805 - 1880 MHz)
  • 2100 MHz (1920 - 1980 and 2110 - 2170 MHz)
So when they do run out of spectrum, what can they do? Well help is at hand in the short term through two new bands which are being released. The first, known as the 'digital dividend', has become available due to the more efficient planning of television broadcast networks that has arisen as a result of the switch-over from analogue to digital broadcasting. The second, at 2.6 GHz, was (and in some countries still is) used for a multitude of purposes including wireless video cameras, wireless cable networks and fixed wireless broadband. Together, these two bands make just over another 200 MHz of spectrum available:
  • 800 MHz (791 - 821 and 832 - 862 MHz) - the 'digital dividend'
  • 2600 MHz (2500 - 2570 and 2620 - 2690 MHz) - note that the gap between 2570 and 2620 MHz is also available
If you assume that an average country has 3 or 4 mobile operators, this equates to something like another 60 MHz (2 x 30 MHz) each, resulting in a 60% increase in their capacity.

So what's the problem? Some observers (eg Cisco) claim that mobile data traffic is doubling roughly every year, so this 60% increase in capacity will amount to about 8 months of traffic growth, then the problem starts all over again. New technology will deal with some growth. Newer mobile technologies from HSPA+ to LTE and LTE-Advanced may offer a doubling in capacity over current 3G (UMTS) networks for each unit of spectrum. Another year dealt with, and only at the cost of changing over all of the network equipment and handsets!

On this front, it is perhaps no surprise that UK mobile operator O2 recently announced plans to offer free WiFi for all. Why is this no surprise? If the traffic from smartphones and laptops can be offloaded from the mobile network to WiFi hotspots, this will ease the burden on the mobile network. But this is a relatively short-term fix too. In the long term, the only way that mobile operators will be able to deal with the growth in data traffic is to get access to more spectrum. But where will this spectrum come from?

It has long been recognised that to offer a sensible (in terms of cost, coverage and capacity) mobile network, frequencies in the range 300 to 3000 MHz are best. Go any higher and things such as Doppler shift and cell handover become real problems. Go any lower and antennas become too large and unwieldy. The problem is that the remaining frequencies in this range are already being used. In general terms:
  • 300 to 430 MHz is military territory
  • 430 to 440 MHz is radio amateur land
  • 440 to 470 MHz is full with PMR systems
  • 470 to 790 MHz has UHF television broadcasters in it
  • 790 to 862 MHz is already mobile
  • 862 to 880 MHz houses all manner of low power devices
  • 880 to 960 MHz is already mobile
  • 960 to 1350 MHz is where aircraft radars and some radio amateurs live
  • 1350 to 1710 MHz is for satellites (including GPS and weather satellites), DAB broadcasting and more tanks, planes and guns
  • 1710 to 1980 MHz is already mobile
  • 1980 to 2110 MHz is partly mobile and partly full of military folk
  • 2110 to 2170 MHz is already mobile
  • 2170 to 2400 MHz is mostly military
  • 2400 to 2500 MHz is WiFi and bluetooth land
  • 2500 to 2690 MHz is already mobile
  • 2690 to 2700 MHz is where radio astronomers hang out (mostly in cardigans)
  • 2700 to 3100 MHz is aircraft and maritime radars
If any more space is going to be made for mobile services, someone else is therefore going to have to give up their claim to their territory. In some countries (eg Sweden) 2300 to 2400 MHz is being made available for mobile services but in the majority of European countries it is used by the defence services who, having already vacated other spectrum, are beginning to fight back.

Clearly, anyone who moves out for the benefit of mobile services will either have to stop doing what they do (unlikely) or go and do it somewhere else (costly). For any international service (eg boats and planes) this cannot be done unilaterally and getting international agreement is probably too slow. What's more, radars and things such as that need a lot of spectrum due to the way they work and furthermore, removing them might cause planes to fall out of the sky, which would seriously disrupt tourism in many parts of Europe that aren't very close to where you live (though it might have a potential commercial upside for undertakers).

Wireless Waffle is therefore going to stick it's neck out and make a proposal as to who should lose the battle for this important part of the spectrum and that is ... the broadcasters!

On a completely different, but not unrelated tack, the amount of energy consumed by a terrestrial broadcasting networks is, well, large. Not 'a whole power station' large, but still pretty big. The amount of energy consumed by a satellite is tiny. In fact, once it's up in the sky, it's zero (they are solar powered). A terrestrial broadcast network also delivers much less capacity than a satellite. So broadcasting by satellite consumes much less power (and therefore has a much lower carbon footprint) and offers much greater capacity (for services such as 'The Cartoon Network' in HD). Let's therefore turn off UHF broadcasting and give the spectrum to mobile networks - the broadcasters can go to cable and satellite and can continue to use the VHF band if they really want to.

What would a world without UHF broadcasting look like. In somewhere such as the Netherlands where 90% or more of homes are on cable, not a lot different. It would mean that people's holiday homes might need a satellite dish but these are so cheap and plentiful it should be no big deal. In the UK where most homes still have a terrestrial UHF receiver you might think this would be a bigger deal, but over 50% of homes have either satellite or cable already and again, having to buy a dish is no biggie, so other than the temporary inconvenience of swapping set top boxes and putting a dish up (or getting connected to cable) nothing much would change.

If they so desired, public service broadcasters could continue terrestrial television broadcasting using the VHF band - by switching off those ancient and largely unlistened-to DAB transmitters. DAB could be replaced by DRM and Bob's your uncle - no loss of anything important, just a bit of shuffling around.

If all this sounds far fetched, watch this space. Or, perhaps more accurately, watch outer space!
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What are the chances (Part IIa)?signal strength
Wednesday 25 August, 2010, 04:10 - Pirate/Clandestine
Posted by Administrator
Back in October 2009, Wireless Waffle brought to your attention the HF (short-wave) monitoring data produced on a quarterly basis by the ITU. Within these reports were a number of short-wave pirate stations and the original list of stations brought a lot of interest from these stations, both to see who had been 'caught' and to see how close the ITU had gotten to identifying their exact location. Based on the e-mails that were received following the article, it seems like some had hit the nail a little too closely on the head for comfort.

To see how the ITU were getting along, and who had been spotted more recently, a trawl of the montoring reports from January to June 2010 has been conducted and the results presented below. Those stations whose name is shown in CAPITALS were directly identified by the monitoring station concerned. Those in lower case have been identified using the various on-line blogs that report pirate reception.

DateTime (UTC)Freq (kHz)Monitoring StationLocationStation
03 Feb 100600-06004025Berlin, GermanyUKLaser Hot Hits
23 Feb 100000-06304025Tarnok, HungaryLaser Hot Hits
23 Feb 101830-23594025Tarnok, HungaryLaser Hot Hits
21 Apr 101830-24004025Berlin, GermanyLaser Hot Hits
02 May 100600-23594025Rambouillet, France0W10 52N01 (Baldock, UK!)Laser Hot Hits
23 May 100000-06304015Tarnok, HungaryLaser Hot Hits
16 May 101900-22125814.7Rambouillet, France0E17 52N45 (King's Lynn, UK)Radio Telstar South
16 May 100700-09155815Rambouillet, France6E11 52N30 (Zwolle, Netherlands)Orion Radio
27 Jun 100630-08205820Tarnok, HungaryOrion Radio
11 Apr 100854-09086203Vienna, AustriaRadio Scotland International
09 Feb 1010486210.2CCRM, BelgiumNetherlandsMISTI RADIO
10 Jan 101818-22466220El Casar, Spain11E24 44N27 (Bologna, Italy)Mystery Radio
20 Jan 101812-23506220El Casar, Spain11E24 44N27 (Bologna, Italy)Mystery Radio
30 Jan 1020026220Baldock, UK10E0 43N50 (Pisa, Italy)MYSTERY RADIO
28 Feb 101100-11376220Vienna, Austria11E0 44N0 (Prato, Italy)RADIO MARABU
06 Mar 101800-23506220El Casar, Spain11E24 44N27 (Bologna, Italy)Mystery Radio
21 Mar 102012-23556220El Casar, Spain11E24 44N27 (Bologna, Italy)Mystery Radio
06 Apr 101852-19176220Vienna, AustriaItalyMYSTERY RADIO
10 Apr 101900-23596220El Casar, Spain11E24 44N27 (Bologna, Italy)MYSTERY RADIO
13 Jun 101730-18006220Klagenfurt, Austria12E0 43N0 (Perugia, Italy)Mystery Radio
14 Jun 101700-19006220Rambouillet, France10E43 43N45 (Prato, Italy)MISTERY RADIO
15 Jun 100700-08006255Rambouillet, FranceNetherlandsCool AM
19 Jun 101530-16456374.1Rambouillet, France4E13 51N59 (Den Haag, Netherlands)Radio Baken 16
09 Feb 1009446299.2CCRM, BelgiumRADIO RAINBOW
30 Apr 101918-20056375Vienna, AustriaNetherlandsRadio Relmus
09 Feb 1009146376.6CCRM, BelgiumNetherlandsRADIO DUTCH WING
20 Jun 101015-16006399.9Rambouillet, France1W45 51N21 (Marlborough, UK)Laser 558 relay
11 Mar 101815-22006870El Casar, Spain9E7 45N18 (Milan, Italy)RADIO PLAYBACK INT
11 Apr 101500-17006959.9Rambouillet, France4E39 51N41 (Breda, Netherlands)Radio Jan Van Gent
03 Jan 1008007610El Casar, SpainItalyRADIO AMICA
10 Apr 100600-21157610Rambouillet, France12E56 43N55 (Pesaro, Italy)RADIO AMICA
11 Apr 100530-06007610Rambouillet, France12E56 43N55 (Pesaro, Italy)RADIO AMICA
10 Apr 101247-14077610Vienna, Austria11E30 44N30 (Bologna, Italy)RADIO AMICA

Please be assured that it is not our intention to name and shame these stations in any way, nor is the Wireless Waffle team opposed to hobby broadcasting (for want of a better word) but we do believe that the stations concerned should be aware that their location may not be as secret as they had hoped.

The question of how accurate these measurements are is a good one. The level of concern that seemed to arise from the previous list suggests that they may be relatively good. However, let's take a real example. There are 10 measurements relating to Mystery Radio. Of these, five different locations are logged. The map below shows the position of these loggings.

mystery radio italy

to catch a pirateThe distance between the closest of all these measurements is around 20 miles (32 km). It is possible that this is the best resolution that some of the monitoring stations can achieve. At this kind of resolution, a ground-based receiver would be unlikely to hear the transmitter. Ground wave signals would not travel this far, and it is the ground wave signal which is required for a person on the ground to be able to 'home in' on the location of a transmitter.

So should pirate radio stations be concerned about being tracked down as a result of the work of the ITU. From the evidence above, it seems that this data alone is probably insufficient to allow a station's location to be identified in one simple move. However, if you are running one of these stations and the location which is shown is more accurate than those for Mystery Radio - and certainly if its within 5 km at which point a man on the ground would be able to track you down - perhaps it's time to up sticks and find a new site!
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Height versus Powersignal strength
Tuesday 10 August, 2010, 05:17 - Broadcasting
Posted by Administrator
One of the most common questions that the Wireless Waffle team are asked by those setting up radio transmitters is, "How much power do I need to cover an area X miles wide?". Such a question is virtually unanswerable as there are so many factors to take account of including the frequency of operation, the topography of the area, the kind of structures (buildings, trees) which are in the required coverage area, what kind of receivers people are using and much more. The observant will note that these factors are not ones which can necessarily be changed by the person operating the transmitter - unless they fancied chopping down a forest for example. What can be changed at the transmitting site are two relatively simple factors: the height of the antenna, and the power of the transmitter.

Such discussions therefore end up focussing on how high the antenna needs to be and what power the transmitter should be. But which is most effective in increasing coverage: height or power?

Let's tackle height first. Assuming we are trying to provide a signal over the earth and that there are no obstacles at all and that the earth has no undulations (hills and so on), then the range of a transmitter can easily be calculated from a simple line-of-sight rule. This tells us that for a particular height above the ground, the horizon (and thus the edge of the coverage area) will be a specific distance away. One oddity in this is that radio signals tend to get defracted a little by the Earth's atmosphere which has the effect of making the planet appear slightly less curved and thus extends the radio horizon about a third beyond the optical horizon. The chart below shows the optical and radio horizons for a transmitting antenna mounted at a certain height.

optical radio horizon

With an antenna about 10 metres above the ground, the radio horizon is about 10km away. If the height of the antenna is increased to 50 metres, the radio horizon increases to about 24 km - a very healthy improvement. It's perhaps worth noting that 'height above ground' could be generated by raising the height of the antenna, or by mounting it on top of heigh point (eg a hill).

Increasing the transmitter power also increases coverage, but not in quite the same way. Getting signals much beyond the radio horizon relies on various odd propagation techniques including refraction, defraction and scatter. In free space, increasing the power by a factor of 2 will increase the distance at which the signal is of equal strength by the square root of 2. So, if the signal is 30 dB at a distance of 10km, increasing the power by a factor of 2 will move the point at which the signal is 30 dB to a point approximately 14km away from the transmitter. Sadly, the Earth is not generally a 'free space' environment and signals fall away much quicker than this, even before the horizon is reached. The chart below shows a simulation of coverage for different transmitter powers, assuming an antenna height of 20 metres.

distance versus power

The distance to the radio horizon for a 20 metre heigh aerial is 15 km and in 'free space', in this example, this is reached by a power of 10 Watts. For the 'real life' example, 10 Watts only achieves a distance of around 10 km because of the fact that the Earth is not a free space environment. To achieve 15 km in 'real life' requires a power of nearer 50 Watts. What is immediately clear is that enormous increases in power are required to extend coverage. Even with 100 Watts, in our theoretical example, the distance acheived is still less than 20 km.

Increasing the height of the transmitting antenna is therefore, theoretically, a much more effective way of increasing coverage than turning up the power. Of course, it's not always possible to put up a high antenna, and in this situation more power is clearly better, but in general height wins every time. To show the difference, the map below (made using Radiomobile) shows the coverage for a transmitter nominally located in the centre of Oxford. It's animated (oo-err!) and cycles through the coverage which would be acheived for:

* A 10 Watt transmitter with an antenna height of 10 metres
* A 40 Watt transmitter with an antenna height of 10 metres
* A 10 Watt transmitter with an antenna height of 20 metres

coverage map example

high receptionThe coverage achieved in the latter two cases is very similar, however in the map with the higher antenna, the coverage is more 'solid' than that with higher power. If this were a radio station, the higher antenna would provide a more reliable signal, especially for people on the move, than the lower antenna with higher power. The extent of the advantage of height over power means that it is generally more beneficial to identify an elevated transmitter site towards the edge of an area where coverage is required, rather than settle for one which is nearer the centre but lower. A transmitter on a hill overlooking a town will provide more solid coverage in the town for the same transmitter power than a site in a town centre. Hopefully, those now considering how best to maximise their coverage will think beyond Watts and consider that factor well understood by estate agents, location, location, location.
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