Wireless Waffle - A whole spectrum of radio related rubbish
Are Murdoch's Sky Satellites Spy Satellites?signal strength
Monday 25 July, 2011, 09:40 - Satellites, Much Ado About Nothing
Posted by Administrator
According to an article in last Friday's London Evening Standard, the term 'pinging' means locating a mobile phone by satellite. Now Wireless Waffle has previously explained that GPS satellites can not track your location due to the fact that they only transmit location information, not receive it. So how did the News of the World manage to 'ping' the location of a mobile phone using satellite?

sexy investigatorAs it couldn't have been GPS, the most obvious solution is that the satellites used to deliver Sky television are not just 'Sky satellites' but 'spy satellites' too! For this to work, the satellites concerned would have to be able to receive a signal from the phone being tracked, identify the direction from which the signal was being received, and then triangulate this through measurements from a number of different locations.

geo earth viewLet's take these one at a time. A geostationary satellite can 'see' about a third of the surface area of the earth. The image on the right shows the view from a satellite sat directly above the Greenwich Meridian. This puts it in clear line-of-sight of at least a third of the Earth's population (and probably more given that the pacific area is largely empty). So could it 'see' a mobile phone in the UK, yes! However, it would also see around a billion other mobile phones. Even if it had a very sharp 'spot beam' focussed solely on the UK (and remember that some celebrities may not be in the UK when pinged) it would still see probably a hundred million phones. Identifying the particular one being used by a certain individual is therefore not at all straightforward. Modern digital signal processing might be able to help a little, but with millions of mobile phones all transmitting at the same time, right across the country, it would take an awful lot of processing to pinpoint just one phone.

Let's assume (for the sake of argument) that such processing could be fitted to a satellite and that it was possible to pick out one phone from amongst millions. The next job is to identify the direction of the signal from that phone. In order to do this to an accuracy of, say 1km, from geostationary orbit, requires an angular accuracy of about 0.01 degrees. To get this level of focus requires an antenna array that is approximately 1km across, nearly 100 times the maximum size of antennas fitted to current communication satellites.

satellite triangulationSo assuming state-of-the-art digital signal processing, and satellites that are 100 times the size of those typically in use, all that remains is to triangulate the location of the transmitter. Typically three measurements are required in order to triangulate the location of an object. All the UK Sky TV satellites are in the same orbital position, but this would not give the level of diversity required and so satellites in other positions would need to be used in addition to the fleet used for the UK services. But as there are Sky TV services for other countries on other satellites in diverse orbital positions, these could be used. This bit, at least, is vaguely feasible.

So with a fleet of gigantic, super-powerful, mega-satellites, it might just be possible to identify the location of a mobile phone from space. It is more likely, however, that the idea that 'pinging' a phone to locate it by satellite is pure hogwash, and is an idea espoused by the press to scare celebrities and others (like you and me) into thinking that they can be tracked down when up to no good!

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Let's sheikh on it!signal strength
Thursday 14 July, 2011, 10:39 - Amateur Radio, Pirate/Clandestine
Posted by Administrator
Around the short-wave world, mention of 'PsyOps' has recently had reason to reappear. It refers to psychological warfare being conducted by NATO forces to 'scare' Colonel Gadaffi's forces into remission through a variety of activities. One of these activities is the broadcast of semi-threatening, warning messages to troops loyal to Libya's erstwhile leader.

commander soloThese messages have apparently been broadcast from a Lockheed Martin EC-130 aircraft known as Commander Solo overflying the region and are using the frequencies which belong to the 'Great Man Made River Authority' (GMMRA) which is Libya's authority responsible for artificially transporting water from wells in the Sahara desert via a big pipe to population centres in the North. Why NATO would have chosen these frequencies is not known, however there is (or was) apparently an ALE network on these channels that was presumably in regular use and hence there would be several receivers across the country in 'important offices' which would hear the PsyOps transmissions.

Frequencies reported in use by the GMMRA in recent times include 4200, 5037, 5047, 5300, 5368, 5768, 6884, 7000, 8161, 8200, 8800, 9218, 9250, 9375, 10125, 10375, 10404 and 11100 kHz. Previous reported frequencies also include 3000, 3900, 4050, 6800, 7805, 7900, 10215 and 10250 kHz (thanks to Btown Monitoring Post).

Of the above, NATO PsyOps transmissions have so far been heard on: 6877, 9376, 10125, 10404 kHz. Note that the 10125 kHz frequency is slap bang in the middle of the 30 metre amateur band but as this is a shared frequency with other services the transmission by the military does not contravene the ITU frequency allocation tables and is therefore, effectively legal. The use of 7000 kHz by the GMMRA is not, however, legal as this is an exclusive amateur allocation. Initially, many of the PsyOps transmissions were jammed (presumably by the Gadaffi regime) however they no longer appear to be so.

Here's the Wireless Waffle recording of Commander Solo on 10404 kHz made at 14:00 GMT on 12 July 2011. The transmission ceased at 14:20 GMT. The noise underneath the transmission also ceased around the same time, however whether the two are connected (ie the noise is an attempt at jamming) can not be confirmed. Given that this recording was made in the UK, it is clear that the power of the transmitter used by Commander Solo and his ilk must be reasonbly high. Judging by the signal strength and general propagation conditions at the time of the recording, a radiated power of at least 1 kiloWatt would seem about right. As normal HF aircraft radios have powers of at least 200 Watts, this seems quite feasible.

uk libya tradeOf course, all that the Colonel has to do to stop the NATO transmissions becoming a nuisance, is hand out free power line adaptors to at least one house on every street and all short-wave frequencies would be instantly jammed. Perhaps Colonel Gadaffi is an investor the Comtrend PLT devices that do all the damage and the reluctance of Ofcom to do anything about them is part of some previous UK-Libya trade agreement on arms sales. Surely now that the UK is part of a force against Gadaffi, Ofcom can now breach the terms of this agreement with the Libyan government to pollute short-wave and finally get rid of the menace of PLT?
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Rraaddiioo Nneeddeerrllaannddsignal strength
Tuesday 12 July, 2011, 14:39 - Broadcasting
Posted by Administrator
Tuning around the 13 MHz broadcast band, Radio Nederland on 13700 kHz being transmitted from Wertachtal in Germany was sounding rather odd. It had a very pronounced echo which made understanding it very difficult (if you could understand Dutch in the first place!)

You will note in the brief recording that towards the end the echo becomes less evident and listening over a longer period it was clear that the echo faded in and out. This can only mean one of two possible things:

(1) The echo was being caused by transmitting the same material, slightly delayed, from a second transmitter site; or
(2) The echo was being caused by receiving duplicated copies of the same material, delayed by some other means.

13700 transmitter site map

As far as was apparent, there were no other transmitters being used on that frequency by Radio Nederland, though there was meant to be a transmitter in China on the same frequency which might have been erroneously relaying the programme by mistake. But the cause is more likely to be some other means. Could it, for example, have been caused by being propagated all the way around the Earth.

delayed beepA quick calculation shows that the delay associated with a round the globe trip is approximately 133 ms (40000 km at 300000 km/s). A snapshot of the pips on the hour is shown on the right, indicating a delay of about 80 ms - so it can't be that! Even if one signal were short-path and the other long-path the delay would only be slightly shorter at around 127 ms so it's not that either.

No other signals in the band were exhibiting the same characteristics which is usually a good sign that it's not a propagation issue (though the BBC Russian transmission on 13745 kHz from the UK did have some very odd rapid fading on it).

The most likely cause seems to be that there were two transmitters on-air at the same time on the same frequency with the same material. Of the other Radio Nederland transmissions due to be on at the same time, all were present and correct which would suggest that it wasn't a transmitter erroneously on the wrong frequency.

Very odd...!
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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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