Wireless Waffle - A whole spectrum of radio related rubbish
LEO: Roaring in the wrong direction?signal strength
Wednesday 23 September, 2015, 12:36 - Satellites
Posted by Administrator
wireless waffle ferretOn several previous occasions, Wireless Waffle has discussed some of the problems, both technical and economic that the raft of companies planning to launch new constellations of high throughput, broadband delivering, satellites may face in making their services a success. Whilst ferreting around the internet, it was interesting to discover a paper entitled 'LEO: Roar or Whimper' which discussed many of the same issues on which Wireless Waffle has opined in the past.

The paper, however, takes a more sideways approach and compares the situation facing new operators such as WorldVu and SpaceX who are intending to launch literally thousands of satellites to provide broadband services, with satellite broadband networks that were planned to do just the same thing in the 1990s (such as Teledesic and Skybridge) but which never got off the ground (so to speak).

leo roar or whimperIt turns out that many of the potential hazards facing today's planned satellite networks have changed little since the 1990s and in some cases the situation may have gotten worse. Take for example the amount of space debris now hanging around at various orbits which is much greater than it was 20 years ago. And though the technology has moved on, the costs of implementing complex satellite earth stations that can track the satellites are no less soluble today than they where when the Spice Girls were topping the charts, even with the advent of leading-edge technologies such as meta-materials. There are a range of other issues discussed in the paper which seems to consider the landscape for the LEO networks to be relatively bleak and foreboding despite many big name investors backing these projects.

For what it's worth, the Wireless Waffle answer to the question posed in the paper's title, 'LEO: Roar or Whimper', is that it seems that the LEOs will roar, but quite possibly directing their volume at people who are wearing noise cancelling headphones and thus won't hear their bellowing cry. Metaphorically speaking!
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ITU roll the dice on the use of C-bandsignal strength
Wednesday 8 July, 2015, 15:43 - Spectrum Management, Satellites
Posted by Administrator
The bedrock of the recommendations posited by many consulting companies involved in radio spectrum management is the cost-benefit analysis. The principal of such an analysis is quite straightforward - you calculate the cost of doing something and then evaluate the benefits of the same thing and compare one with the other. If the benefits outweight the costs, then it should be worth doing. If the costs outweigh the benefits then it is not worth doing.

motorway farm landBut many such analyses are incomplete. As an example, consider the case of building a new motorway over some existing farmland. A typical analysis would look at the costs in terms of the need to find alternative employment for the farmers whose land will be compulsorily purchased to turn into the motorway. The benefits would be calculated to drivers, whose journeys would be shortened and therefore who would save time and money (for fuel). This is not the whole picture: it misses a whole set of costs and a whole set of benefits. It does not take into account the cost of building the motorway, and it fails to consider the benefits being generated from the farmland (e.g. the value of the business being conducted by the farmers). The table below illustrates what a full analysis might look like.

CostsBenefits
FarmersMoving farm to new location or finding alternative employmentRevenue generated from existing farming business
DriversBuilding a new motorway and modifications to existing roadsShorter and faster journeys, savings in fuel consumption

It might also be informative to consider other ways that the same benefits might be delivered, for example by re-engineering existing roads, or by using more fuel efficient cars.

None of this is rocket science and even those studying economics at school ought to be able to identify all of the costs and benefits. It is surprising, therefore, that some otherwise well-respected economists continue to write reports that miss out parts of the analysis. Plum Consulting (no stranger to Wireless Waffle) have recently published a report entitled 'Use of C-Band for mobile broadband in Hungary, Italy, Sweden and the UK'. In it they conduct a cost-benefit analysis of migrating existing spectrum users out of the C-Band (3400 - 4200 MHz) and using it for mobile broadband services. But as with the example above, they fail to consider all the cost and all the benefits. They consider the costs to existing users, and benefits to the new users, but not the benefits to existing users or costs to the new users. The table below summarises their analysis.

CostsBenefits
Existing Users
(Satellite and Fixed Links)
Modifying equipment to allow access by mobile or using alternative frequencies.Not considered
New Users
(Mobile Broadband)
Not consideredHigher speed connections in hotspot areas.

In addition to missing a large chunk of the necessary analysis, they also do not assess alternative methods to achieve the same outcome. For example, no consideration is given to whether the improved spectrum efficiency of 5G networks (which will presumably have started being rolled-out in the timescales considered in the report) would be more cost effective for the mobile broadband operators than using older technology in a new band. The fact that the costs to the mobile operators are not evaluated serves to hide alternative solutions such as this.

ssi c band useOf course the report has been paid for by Ericsson, Huawei and Qualcomm and so it would be expected that the results would show in favour of the mobile industry, and so missing out various parts of the analysis which might make the results less favourable is perhaps no surprise. It is also the case that, for example, evaluating the value of the spectrum to the existing users is a complicated task due to the very wide range of types of users that would have to be considered, from the oil and gas industry to banks, and from broadcasting to humanitarian relief. The Satellite Spectrum Initiative have published a helpful factsheet which identifies and, to some extent, quantifies, the value of the use of C-band to various users. To actually value the C-band properly is a big task which it seems that even the satellite operators who stand to lose most if the spectrum is re-farmed for mobile services, are unwilling to cough up the funds needed to put a figure on it.

itu c band decision makingUntil such time as someone does pay to do the job properly, it seems that all discussions on the value of C-band spectrum to satellite operators or to mobile operators will be conducted without all the facts being on the table. With C-band being a hotly contended issue at the forthcoming World Radiocommunication Conference (WRC) (which will take place at the ITU in November in Geneva) any decisions taken will be rather uninformed. Such important decisions, with billions of pounds of mobile and satellite money involved, should not be taken so lightly. Maybe those users who rely on C-band for their businesses today could club together and raise enough money for decent economics experts to actually work out a realistic value of today's C-band use, and equally the mobile industry could do a full analysis of the costs and benefits of the use of the band, and of other alternatives so that all concerned could be comfortable that they are taking any decisions on a realistic basis.
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How Not To Install A Satellite Dish (Part II)signal strength
Saturday 16 May, 2015, 15:38 - Satellites, Much Ado About Nothing
Posted by Administrator
In the last instalment of 'How Not To Install A Satellite Dish', we successfully installed and aligned a new satellite dish to point at 19.2 degrees East so as to be able to receive German language television (and a few French channels to boot). The next job was therefore to connect the new dish, and the old dish, to the satellite receiver so that the same receiver could be used to switch between the German channels and the English language channels received through the existing, and separate, dish pointing at 28.2 degrees East.

Thankfully this does not (should not!) require the fitting of an additional downlead from the dish to the receiver, oh no. A system called DiSEqC (apparently pronounced 'die-seck' though in reality it should be pronounced 'diss-equck') comes to the rescue. This allows the receiver to select from multiple dishes connected on the same cable by sending control signals along the cable. All that is required is that a suitable DiSEqC switch is installed at the satellite end, connected to both dishes, and to the cable from the receiver.

2 way sat switchA 2 way sat-switch was duly purchased and installed as per the instructions. Back at the receiver (a trusty Foxsat HDR - though the original model, not the new one being sold now on Amazon), the secret menu that allows access to funky multi-satellite functions was accessed (by going into the Setup menu, then pressing red, green, yellow, blue, green, yellow and then blue in that order - or 🌑🌑🌑🌑🌑🌑🌑). Selecting 'DiSEqC 1' from the pull-down menu duly yielded signals from the original 28.2E dish. However, none of the other four DiSEqC inputs yielded anything from the 19.2E dish. Swapping the feeds at the dish end meant that channels from the 19.2E dish could be found on 'DiSEqC 1' but no signals from the 28.2E dish could be found on any setting. Grrr...

4 way sat switchThe DiSEqC settings in the receiver had four channels (e.g. 1, 2, 3 and 4) but the switch only had two. Could this be the problem? Only one way to find out, and so a second switch, this time a 4 way sat-switch was bought (which oddly is cheaper than the 2 way switch at the time of writing!) The original (28.2E) dish was duly connected to input 1 on the switch and the new 19.2E dish was connected to input 2. And guess what - this time success. Now the receiver would find signals from both satellites on the appropriate DiSEqC settings on the receiver.

It is unclear whether this was due to the fact that the first switch was faulty, but as the 4-way switch is (currently) cheaper than the 2-way switch, then anyone attempting this exercise might like to consider just getting the 4-way device to start with and thereby circumventing the tedious hours of failure that might otherwise present themselves.

freesat foxsat menuAnd so now, by switching the Foxsat receiver out of 'Freesat' mode, it was possible to access a wide range of German channels (and the UK ones) but without the help of the Freesat programme guide. Switching back to Freesat mode returned the box to the standard Freesat channel line-up and the programme guide. But surely there must be a way to add the German channels to the Freesat channel menu so that there's no need to go faffing around with multicoloured buttons in the settings menu to switch between them? Actually, there is and at least that part of the job went relatively easily, so stay tuned to Wireless Waffle for Part III of 'How Not To Install A Satellite Dish'...
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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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