Wireless Waffle - A whole spectrum of radio related rubbish
Antipodean Gainsignal strength
Friday 1 April, 2016, 10:03 - Radio Randomness
Posted by Administrator
Despite it being a well-known phenomena amongst radio fanatics around the World, there is little written on the internet concerning a strange effect known as 'Antipodean Gain' and for that reason Wireless Waffle has decided to take it upon ourselves to enlighten anyone who is not familiar with it.

Antipodean Gain can impact any radio wave capable of traversing the globe and therefore mainly applies to short-wave radio signals but in theory could be valid for medium-wave and long-wave signals too if the radio propagation conditions are right. The idea is a relatively simple one: if two stations wishing to communicate are at antipodal points, which put in laymans' terms means that they are exactly on the opposite sides of the planet from each other, it does not matter which way you direct a radio signal from either point, it will be aiming directly at the opposing point.

santiago xian mapTake, for example, Santiago in Chile (70.7W 33.5S), and Xi'an in China (108.9E 34.3N). To within 100 km (60 miles), these two metropoles lie exactly opposite each other on the globe. Thus, no matter which direction you face when standing in Xi'an, Santiago ise around 20,000 km away and the same is true in the reverse direction. If you think about this from the perspective of radio signals: whilst signals normally spread out as they travel away from the transmitting antenna, with antipodeal metropoles the signals re-converge. Therefore any signal leaving the transmitter site will be directed to the receiving site and although they may have originally been spread out, the re-focussing of the signals will mean they add back together and the path between the two will have far less path loss than one which is of a similar length but is not antipodean.

The map to the right shows the World from the perspective of someone standing in Santiago. China is the circle which is in every direction you look, and the very edge of this is the city of Xi'an (the outer circle coloured in red), and so no matter in which direction you look, you will be looking towards Xi'an. The same would be true of someone standing in Xi'an: no matter which way they looked, they would be facing Santiago.

If this is still too complicated, just think of the North and South poles. It doesn't matter which way you face at the North pole, you will always be looking directly towards the South pole (and vice versa). And thus, an omni-directional antenna, which transmits in every direction, when used to communicate with a city on the opposite side of the Earth would effectively be a highly directional antenna, with all of its radiation focused on that city. Signals that would otherwise have spread out would be re-focused into a tight beam.

juan and xinIf this sounds all too unrealistic, work out which country is at the antipodal point of your current location and tune in to a short-wave radio station that is transmitted from that location. For the UK, this is pretty much New Zealand (although strictly speaking, New Zealand is antipodeal to Spain). For the USA and Canada, you are largely out of luck, as the opposite side of the planet mostly comprises the wide, open and empty expanses of the Pacific Ocean.

So now you know. And to help you calculate where your antipodeal point is, just enter your latitude and longitude (in decimal degrees) into the Wireless Waffle Antipodal Point Calculator below, and press 'antipodate me' and we'll do the maths for you. You can then click on the globe to the right and see the your location and that of your antipodal location on Google maps. As they say in France, 'Voila!', or as they say in China, 'Zhli sh'!

Wireless Waffle Antipodal Point Calculator
Your Latitude (e.g. 33.9N)your location
Your Longitude (e.g. 108.9E)
Antipodal Latitudeantipodal location
Antipodal Longitude

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Putting pirates to good usesignal strength
Thursday 24 March, 2016, 12:50 - Broadcasting, Pirate/Clandestine, Spectrum Management
Posted by Administrator
This week, Wireless Waffle took a rare trip to the far reaches of the UK. Or Birmingham to be precise. To be even more precise, the motorways surrounding the UK's second city, whilst en route to elsewhere. The journey gave the opportunity to do a bit of tuning around the FM band to see what's happening in the West Midlands these days. Other than the various commercial stations (including local regional stations Touch FM and Free Radio), and a handful of community stations (including some in neighbouring Coventry), the thing that was most different to the airwaves in the South East was the absence of much in the way of pirate radio.

hot 92 birminghamOnly two pirate stations were heard during the journey:A bit of desk-research has yielded the fact that there arpparently three other stations that are often on the airwaves in the area, including:None of these were heard though.

It's probably about time that Wireless Waffle stopped banging on about pirate radion stations, after all it's now just a year shy of the 50th anniversary of the Marine etc Offences Act whose purpose was primarily to bring down the original pirate stations of the day. The fact, however, that such stations continue to abound suggests that the mainstream UK radio market is failing certain sections of society, which appear to be certain ethnic minorities (Caribbean, African and Turkish in particular) and those who like gruff-beat, wacka-jam and gutter-beat music (or genres with similiarly bizarre titles). It's also clear that Ofcom's efforts to take the stations off-air is not having the desired effect (meaning 'to force pirates off-air').

Information on enforcement activity released by Ofcom under the freedom of information act reveals, for example, that between 2007 and 2012, Kriss FM had its transmitters taken off-air by Ofcom 17 times and its studios raided 6 times. Hot92 had its transmitter raided 42 times and its studio raided 3 times. Sting had an astounding 60 transmitter raids (and 3 studio raids) over the same period.

ofcom raid rooftopWe recently discussed the idea that pirate radio could move to small-scale DAB radio services, or conversely that the closure of regular FM services might open up the FM band as a playground for even more pirates. But could there be yet another option... If Ofcom were to cease all enforcement activity on pirate radio (except in casese where it was causing interference to safety-of-life services) and let the illegal broadcasters run riot, the amount of intereference they would cause to legitimate stations would increase and this might be the incentive needed for those listeners to finally go out and buy a digital radio! So instead of continued enforcement, why not leave the pirates alone and see if that has the desired effect (in this case meaning 'forcing a move to digital radio').
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CBGB (Citizens Band Great Britain)signal strength
Friday 11 March, 2016, 13:34 - Radio Randomness
Posted by Administrator
dukesofhazzardWireless Waffle has been contacted by Will Hogan who is putting together a book entitled 'CBGB' which will celebrate the culture of CB radios across Great Britain in the 1980s. To let Will take over the commentary:
Inspired by the amazing artwork of Eyeball cards, we aim to interview enthusiasts to get a real insight from the people that made it happen, and explore the cards themselves.

We already have a bank of cards from Suffolk, and a few interviewees, but we really need more to show the national scope of CB culture at this time. I'll be working with award-winning photographer, David Titlow who specialises in portraits (his work can be seen at the National Gallery as he's the latest recipient of the Taylor Wessing portrait prize).

Absolutely any help we could get - even looking at Eyeball cards that anyone has - would be amazing. There's no pressure to talk or be quoted, but anyone who would be willing to would be fantastically helpful.

If you could help Will out, please get in touch with him. His telephone number is +44 (0) 7966 072826.
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Is the UK overpaying for the digital dividend?signal strength
Monday 29 February, 2016, 08:16 - Broadcasting, Licensed
Posted by Administrator
Some time ago, Wireless Waffle discussed the various bidders to provide the television transmitter network for the UK's fledgling local TV stations. As part of this, the company responsible for providing the transmitters and masts for all of the other UK digital terrestrial television stations, tax evading transmitter supremos Arqiva, provided indicative figures for the costs of building the local TV transmitters. Their 'Reference Offer' details, on a site-by-site basis, the costs, as Arqiva saw them, of providing the requisite service together with the cost of providing 'network access' only (e.g. the rental of space on their masts). The figures vary by a factor of about 8 to 1 between different sites. But to what extent are Arqiva beefing up the actual costs to make a profit on their largely monopolistic position?

sheffield tv transmitterMaybe an example would be useful, so let's consider their proposals for the Sheffield transmitter, one of the cheapest in their offer. Their prices are as follows:
  • GBP 147,397 one-off costs, and;
  • an annual fee of GBP 17,783.
The one-off costs include site planning, preparation and installation, antennas, transmitter and multiplexer and the annual fees include rental of the site, a management fee, electricity, rent, light and heating.

According to Ofcom's local TV feasibility study, the technical details for the Sheffield site are:
  • Frequency: Television Channel 55, vertically polarised
  • Transmitter power: 100 Watts e.r.p. requiring a transmitter output power of 28 Watts (taking into account antenna gain and cable loss)
  • Antenna height: 43 metres
  • Antenna type: 2 x log periodic on a bearing of 110 degrees
Let's start with the stuff we have to buy. A 28 Watt DVB-T transmitter costs around GBP 10,000. Antennas can be had for GBP 100 each and we need two. Cable (let's assume 60 metres to allow a few metres at the bottom of the mast to reach the transmitter and a few left spare) of LDF4-50 which gives less than 3dB of loss, is around GBP5 per metre, making a total of GBP 300 for the cable. The mast of the tower is 52 metres high, so let's assume GBP 2500 to make space for the local TV antenna. And to be generous, let's add in another GBP 5000 for sundries such as connections to electricity, rack space and so on. Much of the remaining DTT functions (e.g. multiplexer and encoder) can be done in software, so GBP 2500 for a high-end PC to do some storage, playout, encoding and multiplexing. This makes a total capital spend of GBP 18000. Even accounting for a very healthy profit margin this means that Arqiva are charging well over GBP 100,000 for 'site planning, preparation and installation'. Maybe television engineers are particularly expensive in Sheffield?

working on transmitterAs for the annual costs, let's say it requires a visit every month to check on how it's working and this is one person dedicated for the day (though no doubt they would be checking on all the other transmitters on the site too), at a reasonable estimate of GBP 500 per day, to include the cost of petrol and transport, this equates to GBP 6000 per year. The power required for a 28 Watt transmitter assuming it is 20% efficient, is 140 Watts (equating to 1,227 kWh of electricity per year) which at today's prices would cost around GBP 122 per year. Allowing a further GBP 500 per month towards the maintenance of the buildings, air conditioning, mast and so forth (noting that these will have already been paid for by the existing tennants), the total annual fees would be around GBP 12,122. The annual fee proposed by Arqiva is therefore not as badly over-egged, no doubt the 'management fee' covers a lot of this difference.

So, in conclusion:
  • Arqiva seem to have extensively overpriced the capital work associated with providing and installing the local TV transmitter; but
  • The proposed annual fee seems much more reasonable.
Moving forward to today, the European Commission has just published a report by consultants LS telcom and VVA which, amongst other things, examines the cost of changing the frequency of all the digital television transmitters in Europe to clear the 700 MHz band, whilst at the same time migrating to DVB-T2. The costs detailed in the report, catchily entitled, 'Study on Economic and Social Impact of Repurposing the 700 MHz band for Wireless Broadband Services in the EU', are that to do this mammoth re-engineering task would cost between EUR 456 and EUR 888 million.

The study makes the assumptions that:
  • Existing antennas are broadband and can be re-used;
  • Existing transmitters will be upgraded rather than replaced.
These two assumptions are open to challenge. Whilst most new UHF antennas are broadband and thus in theory would not need changing, there can be instances where antennas have been designed to provide very specific radiation patterns (e.g. to provide nulls in certain directions for co-ordination purposes) and thus a change in frequency would affect their radiation pattern and may require a new antenna. Evidence suggests, however, that the transmitters themselves should be able to be converted from DVB-T to DVB-T2 by only replacing the modulator.

dvb t2 conversion
Source: Assessing the technical requirements and implications of DVB-T transitions

The 'cost per transmitter' given in the report ranges from EUR 20,000 to around EUR 50,000, which seems reasonable given the assumptions made. Arqiva's estimate for re-tuning the UK's transmitter network to clear the 700 MHz band provides values ranging from GBP 310 to GBP 470 million (approximately EUR 400 to EUR 600 million) putting the price for re-farming the 700 MHz band in the UK at approximately the same level as the Commission report identifies for the whole of the EU!

There are approximately 1,200 transmitter sites in the UK, the smaller ones with three multiplexes on them and the larger 90 or so with six, seven or eight, making roughly 4,000 transmitters in the UK. Taking the consultants' report's 'per transmitter' value, the price for re-farming the spectrum in the UK ought to be nearer to EUR 80 to 200 million, a factor of 2 to 8 times removed from the prices quoted by Arqiva, depending on which end of the ranges quoted you take.

So who is right? It seems that the two reports are doing something slightly different:
  • The Commission's report assumes that existing multiplexes and frequencies are converted to DVB-T2 and as such fewer are needed. In only very few cases would there therefore need to be a change in frequency, as the additional capacity of T2 (and MPEG-4) would mean existing frequencies could largely be re-used.
  • The Arqiva report is trying to move all existing multiplexes (whether DVB-T or DVB-T2) to new frequencies, which is (clearly!) a much more expensive undertaking.
arqiva happy moneyPerhaps Ofcom should take a leaf from the Commission's book, and instead of trying to re-engineer the UK's DTT network to be the same, should instead take the opportunity to convert the network to be DVB-T2 only and save a lot of money in the process. Given the timetable for the clearance of the 700 MHz band (e.g. around 2020), and that typical television replacement cycles are 7 years, the average British household would already have a T2 receiver by then... Then again, no doubt Arqiva could find some 'management costs' to soak up any savings!
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