Installing a Sky dish

I'm not an expert but I've been messing with dishes since the days of Sky analogue so you might find this useful.

Here's a typical Sky "minidish" fixed directly to a wall with a bracket. The bracket allows minimal adjustment for elevation (up down tilt) and for sideways alignment. This type is useful where the wall almost faces the satellite. It has a special "universal" LNB on its arm.

Most Sky minidishes are supplied with a 1.5 inch diameter tube and separate wall mount bracket, which allows a much wider angle of east/west adjustment.

The "Sky Digital satellite" is actually a cluster of satellites positioned above the equator and 28.2 degrees east of the meridian. So (in the UK) your dish will point in a south easterly direction and must be aligned extremely accurately because that tiny cluster of satellites is about 23,000 miles away.

This is a larger dish. It's actually about 80cm in diameter and I think it's made under the name of "Orbital". It has a standard "40mm neck" universal LNB clamped to its arm.

This is another 80cm dish. This time it's a "perforated" dish. It's just a solid dish which has been perforated all over with little holes. The perforations allow it to blend in with the background a little better for cosmetic reasons.

Those metal legs that you see are actualy a tripod wall bracket. The centre leg is formed from a 2 inch diameter tube.

These wall brackets are a bit tricky to install. It's a good idea to rest the legs on a large piece of paper or card and mark the hole positions. Then you can fix the paper to the wall and tap a nail or centre punch through to mark the hole positions on the bricks for ease of drilling.

The satellite cluster is so far away that the signal reaches Earth in a tight beam. The dish acts as a parabolic mirror and focusses the signal onto the end cap of the LNB. In case you didn't know, "LNB" stands for "Low Noise Block-downconverter". That's because it collects the whole "block" of very weak microwave satellite signals and converts them to a block of lower frequency signals so that they can pass down the coaxial cable to your receiver.

Notice that the LNB support arm is NOT pointing at the satellite cluster. In the UK, the arm will be almost horizontal. Further south it will be tilted upwards more.

The direction of the satellite varies with your location. To calculate the angles, you can download SMW Link, at http://www.smw.se

Sometimes it's undesirable to positon the dish on a wall because there are trees blocking its view of the satellite or because it would look unsightly. In this instance it may be possible to mount the dish at the opposite side of the house on a pole so it is looking up the roof at the satellite. More information in this PDF document.

You can paint your dish to blend in with the background. Here's a picture that I found. The minidish has been painted white to match the wall. It's barely noticeable now.

OK, so you first need to assemble your dish then fix it in place. It doesn't need to be high up - you can install it in a hole in the ground if you wish - as long as it can "see" the satellite.

In the UK, the satellite will be between 20 and 30 degrees above the horizon - higher as you go south. You can check this by using a cheap school protractor and a piece of cotton with a weight tied to it. Much cheaper than an inclinometer!

I won't go into details of the actual fixing here; if you can't manage it, or you are unwilling to climb a ladder to do it, then you're unlikely to be able to align the dish either! That's when you get in the professionals. (I downloaded an excellent book "Installing Sky Digital TV" from Satcure which I'm sure you will find indispensible as it gives far more information than I can put here. There's over 100 pages of instructions and pictures).

The satellites broadcasting Sky Digital (there's more than one satellite) are located above the equator at a longitude 28 degrees east of the meridian. Now, Greenwich in the UK is on the meridian line (zero longitude). So, if you look directly south and imagine looking at the top of a big ring encircling the earth, that's 0 degrees. Now let your eyes move east (left) along the arc that's curving down to the left. At 28 degrees (out of 360 for the full circle) you'll be looking towards the Asta 2 satellites.

Point your dish roughly in that direction then use a satfinder meter to locate the satellite. You can do it with the Digibox but it's not as easy. Expensive digital meters will analyse the signal and tell you which satellite you have found automatically and instantly!

If the dish is on the ground, the TV can be right next to you (but plug the extension cable into an RCD for use outside).

Connect the LNB to the receiver's input with a length of satellite co-ax (make sure you have the right sort of cable), switch on the receiver and TV and select the signal level display on the receiver. With a Sky Digibox, you press Services-4-6, but all digital receivers have some sort of signal level display.

The display shows the overall signal level or strength received on the "default transponder frequency" only; the signal 'quality' (a measure of the correct digital data received) and an indication of the signal 'lock' (when the correct signal isfound).

If you're very lucky, on connection, the level and quality meters will surge up and the indicator show the signal locked. But more likely, you will have to search a little to find the satellite. Starting from your first guess position, move the dish left and right and up and down to scan the sky. Move in small increments or you will move past the satellite.

In addition, look for the following information on the signal menu screen:

Astra 2 at 28.2'E
Network ID = 0002

Astra 1 at 19.2'E
Network ID = 0001 (this is normally 000 unless you alter the default transponder FEC to 3/4)

Hotbird at 13'E
Network ID = 013e

This tells you which of the three most popular satellites your dish is aligned on. If it's not the one you want, simply swing your dish in the appropriate direction. Easy!

Fortunately, the small dishes used for the major satellites these days have a wide 'beamwidth', and so they will get a portion of the signal even if they're not aimed well at the satellite - enough to alert you that you're getting close.

When the dish gets a glimpse of a satellite, the level meter will register (the quality and lock indicators may well do nothing). With many receivers (including the Sky Digibox) there's a distinct delay before the menu display registers the signal, so this whole process must be a slow one of move-wait-move-wait. The advantage of a separate signal level meter is that the response is near enough instant so you can sweep the dish, watching for a kick of the meter.

The scanning process is repeated, centred on the new position to get a stronger signal, until the signal quality meter registers about 33 per cent, changes colour from red to green, or otherwise shows it's found a digital signal, dependent on your receiver.

If you have found the right satellite, the lock indicator will come on (or on some receivers, the search channel flicks into life). Now set your receiver to perform the full search and check that you get the expected channels (with a Sky Digibox, that happens automatically - it will find the EPG listings if you have 28'E in your sights).

If you get no channels, or ones other than expected, you have the wrong satellite and the whole procedure needs to be repeated from the start. Refer to our Network ID list above.

When you've found the right satellite, you should tweak the alignment for the best possible signal, using the signal quality display. If you find that you get a 100 per cent reading (only likely with an over-sized dish), temporarily cut down the amount of signal reaching the LNB by draping a wet cloth over some of the dish reflector, and home in on the very best (diminished) signal. This works because water absorbs the microwave signals from satellites very efficiently.

The last task is to set the 'skew' of the LNB (its correct rotational angle in its holder). With a Sky minidish this is sometimes preset. Otherwise, with the damp cloth in position, rotate the LNB to find the strongest "signal quality".

When you have all the adjustments correct, tighten up the various screws and bolts to lock the dish in the right position (tighten pairs of bolts evenly so the dish is not pulled out of position) and run the cable to where the receiver will normally reside.

Without any kind of meter, this whole process is very lengthy and often frustrating but you should now have your dish accurately trained on the satellite. If it is well aligned, the onset of rain or even light snow should not affect the picture and you will not have to repeat the process again - until you want a larger dish, a different satellite, or you move home.

Note: If you get everything working fine but some programmes are missing, it may be helpful to use the "Manual Tuning" menu method. This is described quite well with screen shots on the SatCure site, technical section page 10.

Here is a movie that shows the use of a simple alignment meter. (You will need "Flash" plugin installed to see it:-

To connect the LNB, first to a meter or a receiver placed near the dish for alignment, and later to the receiver in its final position, you must learn how to make up a cable.

Use screw-on F-connectors. The crimp-on type can perform better but they require a lot more practice and a special crimping tool.

1. Use CT100 cable or equivalent (double shielded with copper braid and copper foil. RG6 will do but the copper braid/aluminiurn foil is more likely to corrode outdoors).

2. About 25mm from the end, cut through the outer plastic covering with a sharp knife and remove it. Do not cut through the braid beneath

3. Remove the exposed foil and twist the braid together to one side

4. Cut and remove the inner insulation (don't cut the centre wire) to leave all but a few millimetres of the wire exposed.

5. Twist the F-connector on to the cable as far as it will go (until the inner insulation hits the baffle inside

6. Finally, trim off the exposed braid and cut the centre wire to be just proud of the F connector

(Info from What Satellite TV magazine)

IMPORTANT:

While most shops would have you believe that the particular "F" plug they stock will fit ALL sizes of cable, it's simply not true! If you screw a plug designed for WF100 onto RG6 cable, it will be too loose and could fall off. Conversely, if you screw an RG6 plug onto WF100 cable, you'll damage the cable and cause an impedance mismatch.

Take a look here for proof.

Q. I have a Sky+ Digibox. How do I tell which cable goes to input 1 and which to input 2?

A. It doesn't matter which cable is connected where. The outputs of a twin- quad- or Octo LNB are all the same.

More information about installing on Dave Sullivan's site (see Links page). Also a good book that you can download here.