digital tv switchover

Rob is generally correct about his alignment procedure, except that it probably isn''t clear where to point the antenna. From UK, all geostationary satellites are towards the South, and are further specified as so many degrees East or West of 0 degs longitude - so a satellite at 28.2 degs East is actually 28.2 degs East of due South (0 degs) - i.e point the antenna South, the move it to the East (left) of the due South line.

 

Unfortunately, its not quite as easy as this - the bearing is from 0 deg longitude, so if you are not at 0 degs, the angle is changed slightly. Similarly, the elevation angle is lower depending on how far north you are. However, it is not difficult to find the satellite - simply connect up the receiver to the antenna, set the receiver for almost any channel, and slowly move it in a ''raster'' pattern, starting from a few degrees above and to one side of the expected angle. move the antenna horizontally (slowly) , until it is pointing a few degrees to the other side of the expected azimuth if no signal is seen, then tilt the antenna down a fraction (maybe one degree), and swing it back to the left. If this is done slowly in small increments, it should be possible to find the bird. There are several birds in this region - check you have found the correct one ( see http://www.satbeams.com/footprints). To make this even easier, many receivers (even cheap ones), have a tone output (derived from the system AGC, for the technical) which changes when it is receiving the satellite beacon signal - look in the instructions and user menus).

 

As Rob says, some channels are horizontally polarised and some are vertical, and there can be signal level differences between them, but in the UK this is relatively insignificant - simply adjust the antenna pointing fractionally to get the best visible output for a channel on each polarisation (i.e., and average setting), and fix it in this position. The signal strength with a 60cm dish in the UK is sufficiently good that the difference is not significant. I have a meter (try Maplin, Conrad, etc - they are very cheap), but I have rarely used it - I use the technique described above.

 

I used a cheap (35 Euro) digital receiver and a 60 cm dish in Central Germany to receive perfectly good Freeview reception from the inception of the service, so this must be possible from almost all locations in UK - there is absolutely no need to pay the rip-off prices demanded by various companies. As John Coates says, you can get all BBC and ITV regions plus other channels, if thats what you want.

 

There are many channels available - we receive some UK channels in Romania, again using a simple cheapo digital receiver and an 80cm dish. We cannot see BBC and ITV (the satellite footprint is shaped so as to cover only UK (plus most of western Europe), but we get BBC 24 hour and Sky news, plus about 10 other channels showing films and various series, and sports - all for zero cost. HD channels are also on these birds, but you will need an HD receiver, and even then, the majority of these channels are scrambled (try browsing this site http://www.lyngsat-address.com/ for full information on the channels carried on these birds), so you will have to pay the rip-off artists anyway. I believe also (not 100% sure), that some of the channels which are available free and unscrambled on terrestrial Freesat are also carried on the Freesat satellite service - but I understand they are provided through Sky and are ''soft-scrambled'', so even though they are on Freesat you still need a Sky card. I think this is provided free on request for the Freesat channels - but you will then need a receiver which can read the card (NOT necessarily a Sky box). This probably explains why John Coates could not receive any HD on his ''HD-ready box''. I don''t know of any ''free-to-air'' HD channels at moment. This is probably all in the interests of obfuscating what is a fairly simple system, and to increase the money going into a certain Australian pocket.

 

Please don''t moan at me if your experiences differ from mine - I retired from this industry after 45 years in it, and left UK for good many years ago - I provide the information in good faith, with the comment that a digital dish and receiver (NOT Sky) are very cheap (less than 40 UK pounds if you look), and you don''t need to mount the thing on the roof - so long as you have a clear view of the sky to the South it can be at ground level, so have a look for yourselves.

Although this thread is not really connected with model engineering, it is not offensive or controversial and can remain in place.

regards David

 

Well, I think it is connected to ME. I'm just waiting for a dish etc. to be delivered to get Broadband, then I can watch all the useful videos. BT is rubbish and can't supply reliable broadband. We have only digital telly now, rumour has it that the power is turned down at weekends to reduce the chance of faults, so that staff don't get called out. Certainly lose channels at weekends. Am looking to get a dish for TV also. Lots of useful information here.

 

It's pretty amazing what you can learn in here.

Thanks to all who gave advice on how to align a sat dish - I have saved the information elsewhere before all of it gets binned again!!

 

Regards,

Chris

Hi There

I get good broadband from BT and crap from Sky.

I only keep both in case one of them goes down so I can continue with getting the magazines out with the other.

regards David

 

Seeing the comments to the Moderators deletion of the original postings on this thread, perhaps it is time to define some rules as to what will result in moderation action, and the consequences.

 

I would suggest (as a start) that the only reasons for deletion should be personal abuse, porn content and obvious spam - what do you think?

 

I support the idea of OT material because it is clear that it is welcomed by many people, and there is always the possibility that further interest will be generated by OT ideas and information.

 

 

Hi

 

Perhaps a section for 'Non Engineering' topics could be opened, that way quite a lot of useful bits n bobs could be posted without too much fear causing offence.

 

Just an idea.

 

Cheers

 

Martin

Hi There

This site has no proper system for suspension.

We can make a member bozo which means they can't be seen but thios just leaves holes in the posts.

Not a good idea.

regards David

 

Posted by Martin W on 20/08/2011 01:07:32:

 

That works, but not without rules. After running a forum that has one of these for the last 12+ years, I think I've discovered what most of them are - well, enough to forestall most of the issues that arise, anyway.

 

First, you have to understand what the problem is (just like engineering, really). If a forum has a community of users based on a common issue/hobby/whatever, the chances are that their attitudes to this will share at least some common ground. It's important to understand though, that this doesn't necessarily extend to any other subject at all. And that's where all the trouble starts when it comes to an OT forum. So the rules have to reflect this. And as a result, we've had absolutely to ban any threads about religion, politics and now, believe it or not, global warming! All of these topics have caused major fallings-out of people who otherwise get on quite well. And none of the topics has anything in the slightest to do with what the forum's about.

 

Typically, a post like David Southwell's above is likely to incite at least a little ill-feeling, even though it's not aimed at anybody in particular, and I would like to think that once he's considered it in that light, he might want to withdraw or edit it. Thing is, he can't do this on his own after a very few minutes - he needs a moderator to do it. And that's wrong. We've found that allowing people to edit and even withdraw their own posts after the fact has actually saved a lot of moderation and also quite a bit of ill-feeling - people often write things in haste that they wish upon even quite short reflection that they could withdraw, and here they simply can't. As a result of letting people edit their own posts, the place runs a lot more smoothly, and I hardly have to intervene at all.

 

Bottom line - you have to trust people. Most people behave sensibly most of the time, and aren't anywhere near as devious and manipulative as David thinks they might be - especially when they feel as though they are slightly more in control of the environment they're in.

 

I'm not going to provide a complete set of forum rules (although we have them), but there are a couple which sum up most of this:

 

1. You should post in a way that is respectful towards other users.
Abusing users in any way will not be tolerated and will lead
to a warning.

 

2. We will not tolerate any harassment based on sex, race, color, creed,
country, religion, age, sexual orientation, class, or political opinion.

 

No. 2 could lead people to a complete ban, but I've not had to do that yet. We do, though, make it a requirement for forum membership that people have read the rules, and tick a box stating that they agree to abide by them.

 

But, if you ignore basic human nature, it's going to come back and bite you - quite a lot.

 

Just like it does here....

 

Hi Chris and others

 

Here is a simple way to set up a dish using two sheets of paper.

 

1. Go to http://www.dishpointer.com/ enter your location Blogtown, Blogshire, UK and this will show your district on a map. It opens with a US location!

 

2. Use the map to locate the dwelling on which the dish is to be mounted.

 

3. Select the Astra 2 satellite ( The other satellites have different services so make sure you select the correct one as the angles are very different!)

 

4. Check the box on the map to show obstructions.

 

5. Use the obstruction point to pick the best location on your building or garden for the dish and increase map scale to maximum magnification. This is also an indication of how far up the wall you need to mount the dish. This is simple trigonometry but the method described below is so simple and is probably quicker.

 

6. Check that you can achieve sufficient height to clear the obstruction. Move the marker corresponding to the dish around the property and select the best location. Now for the elevation check you do this by measuring along one edge of a piece of paper the number of units from a square (90 degree) corner. Mark this edge HORIZONTAL Now measure from the same corner the height of the obstruction using the SAME scale! Now fold the paper along the line joining the two points measured earlier on adjacent edges. This is the elevation for the dish above the horizontal.

 

7. From the printed map fold along the line of the surface from which the dish will be mounted. Then fold along the line to the satellite. This is the angle of or the dish when mounted on the wall. Just make sure you do not turn the paper over!

 

8. From the point on the building on which the dish is to be mounted use the Second piece of paper to show the direction of the satellite as an angle from your selected mounting surface. Note this avoids any problems with a compass pointing at local metal work etc. Then use the first piece of paper to check there is a clear view of the sky - no buildings - trees or other objects by sighting along the paper. Use the second piece of paper to check and re check that the view of the sky at the elevation angles given by the two bits of paper is clear - then - and only then mount the disk brackets. Where obstructions are found the at the angles required for free sky view the dish position selected is too low. It is possible to use the elevation angle to calculate the height above ground level but I have not found this necessary in practice as a quick check by sighting is so easily done from the ground and ladder as necessary.

 

9. Tweek the mounting adjustments on the dish to get the angles for both elevation and bearing from the mounting surface. Nip the adjusting screws and chek the signal strength monitor on the receiver set up page for the Astra 2 satellite (There are various letter suffixes which indicate which transponder you are tuned to be it Freeview or Sky this only affects the tuning range of the TV or set top box not the dish position. If the signal quality is not sufficient then move the dish on its adjustments but check first that it is properly aligned to the bits of paper.

 

10. If the paper angles have been adhered to as well as plotted accurately then no tweeking should be necessary. I find this method is quicker than using the meter compass and can save a lot of debate on positioning in sensitive locations!

 

Just make sure the dish is mounted where it will not be disturbed.

 

Also for most LNB the leads should come out of the bottom for the correct polarisation and the fine tweeking of the angle is done using the signal strength meter either in the TV or STB or a separate meter if available.   

 

Regards - Pat

Thanks for all that Pat,pity I've just come in after fitting my new dish, oh well. It's for broadband, and suppliers have forgotten the paper work, so don't know yet which sat. to point at. So will go for a pint. My second point, about posting in forums. I am new to all this, I usually write as if i'm talking to somebody in the pub, this can cause problems, because who knows if I'm joking for instance. But as a Yorky living in Scotland do have to be very careful what I say

Pat Thanks I live in Hungary I have found your link most useful. Al I need now is to find which satellite the Beeb/ITN use and thei frequencies Then I will need get hold of the sheet metal.etc I need for a 2 Meter dish.
Oh by the way the Variation in Hungary is Zero degrees

I am glad to hear that Beckley is closing I used to be able to see it a few miles away from where I lived but could never get more a light sizzle from it. They never found out why, but i did!

regards

Dick

Hi Dick

 

If you are going to make your own dish. An easy method is to use a large block of high density foam plastic that is friable.  i.e breaks into crumbs when rubbed. Make a spade cutter out of a bit of sheet material to the correct parabolic shape. Plunge the cutter into the foam with care and a light action as the cutter is large and the cutting edge less than rigid! I have made 1 meter diameter dishes this way but 2 meter may be too big. Lay up horizontal tinned copper wires at 5mm intervals and press down into the foam and secure. Leave all wires 100mm too long to permit soldering to the edging tube. Bend and solder cross wires to complete the mesh and bend a hoop of copper tube to make a neat edge when soldered in place.

 

Remove all traces of the foam by what ever method appeals. Result is a dish with minimal visual impact good performance (provided you have kept to the profile) and low windage. The windage is important as the angle subtended to the satellite is very small which means that wind rocking the dish can become an issue particularly in exposed situations.

 

A previous contributor has given a good link to a site that shows how big a dish is normally required for any given location / satellite.

 

Just check the price of a suitable metal sheet against the cost of a commercial dish as the sheet of metal may be very expensive by comparison. Try and use a better quality LNB if you are on the fringe of the service area.  But do check the satellite operators site for recommended dish sizes along with the stations broadcast on each of the transponders to make sure you are going to get the required entertainment!

 

For Gordon,s benefit just enter Astra in to Google to list the services provided by the transponders on Astra 2 I think 2D is correct but this is from memory so please check - however since they are all on the same satellite it only comes into play when starting up the receiver.  Note the 2D transponder is beamed at the UK.  

 

 

 

Good luck - Regards - Pat

There may be one simple way of transfering the azimuth angle from an already lined up local dish to another. Just watch the shadow of the LNB from about 10.25 am GMT find the time when the shadow is on the centreline of the dish. When you have the shadow on centre set up the other dish. As the Earth rotates at 15 degrees/hour or 1 degree every 4 mins this is quite a sensitive test.The only big issue is cloud in the UK! If only we would get a bit more Sun.

 

Pat's method is certainly one way of making a dish. Often larger dishes appear as surplus but lots of people make them out of "chickenwire" on ribs, glassfibre dishes cast on foam or wet sand or by riviting sheet segments together. The latest ultra low noise blocks allow much smaller dishes to return the same performance as the old big ones.

 

Billy.

Ha ! Pat :- this is what Catch 22 was all about . Can't get decent internet via BT, seems my wires are to long, so stuck with sub 9K until I get the dish set up, What sat ? Not arial, I know it's not a TV sat, must wait 'till Mon. to contact agents. Could go on line ,search the net, but can't, catch 22.

Pat Thank you for that idea. But you have to know the frequency range you are trying to receive. Long ago I used to make telescope mirrors which were figured to parabolic to within ¼ of the wavelength of the mid spectrum. Figuring the mirror closer that that was a waste of time as improvements had no effect. The light could not see it! A mate of mine was on the 935 MHz CB. Wave length a little over 3 mm His dish was almost conical in section. One also has to consider the ‘F’ number of stop of the mirror as this gives you your ‘magnification’ and light receiving power.
Rgds

Dick

Hi Gordon

 

Commiserations over your poor internet speed. Think the satellite service you are signing up to is at 39.0 degrees East and for the North of Scotland 14 degrees elevation or 15.5 degrees further South.

 

Good luck for high speeds soon. Regards - Pat

 

 

Hi Dick

 

As far as I am aware there is little impact of frequency on the design of the dish. The diameter to depth is mainly a function of the mechanics of illuminating the horn of the LNB. This is very different from an astro telescope where the aim is to bring the wave to an actual focus. The LNB has an active area of approximately 10mm square.

 

The frequency (low GHz) is important when the dish is perforated or formed from slats. If the holes are too big or the slats the wrong dimensions the surface ceases to act as a reflector and the dish becomes transparent. The long range radio fraternity use very high gain aerials to get extra long range communications under ideal (freak) conditions. For reliable satellite reception a few extra dB are required to cope with rain clouds (10 dB is typical) but other wise the signal is reasonably constant as there is little weather in the path from the satellite. To get a reasonable signal to noise ration the gain required is low because the aerial is looking into space and is thus not picking noise from man's activities which involve the use of electricity.

 

To see how all of this influences the design and construction of a 2 meter dish draw the thing out to scale and pick the way the dish gathers the beam and projects it onto the LNB as this is the best way I know of showing how the various LNB feed arrangements work. Regards - Pat