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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Sky Dish Adjustable LNB?
I have just come by a sky dish and notice that there appear to be different
positions for the cable inlet. The connection is in like a notched groove, with numbers 1 to 5 above the notches. Effectively the cable connection itself can move into the notch cutouts. These have become worn and the connection has moved - so the questions a What difference does this setting make? Presumably this affects the receipt of signal? TIA Phil |
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On Fri, 14 Jan 2005 09:40:03 -0000, "TheScullster"
phil-at-dropthespam.com wrote: I have just come by a sky dish and notice that there appear to be different positions for the cable inlet. The connection is in like a notched groove, with numbers 1 to 5 above the notches. Effectively the cable connection itself can move into the notch cutouts. These have become worn and the connection has moved - so the questions a What difference does this setting make? Presumably this affects the receipt of signal? Put the damn thing up on your house and try it! :-) Digital satellite reception is not as sensitive as some might suggest. I get mine using an old white analogue dish with a universal LNB attached. The only problem is that the dish being solid rather than made of gauze, it blows more in the wind. The recent winds have blown the dish very slightly out of place. If you're using a sky box, the quality indicator is more important than the signal strength indicator. Get the quality indicator as high as possible. M. |
#3
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Looks like you have a multiple LNB (they are usually installed when you have more then one skybox,
And as you have five, I take it that you have sky digital plus But all should work |
#4
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"TheScullster" phil-at-dropthespam.com wrote in message ... I have just come by a sky dish and notice that there appear to be different positions for the cable inlet. The connection is in like a notched groove, with numbers 1 to 5 above the notches. Effectively the cable connection itself can move into the notch cutouts. These have become worn and the connection has moved - so the questions a What difference does this setting make? Presumably this affects the receipt of signal? TIA Phil I saw something similar on my LNB - I thought it was to adjust the angle the LNB points at. I think mine had a screw next to the numbers 1-5 though. Bob |
#5
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TheScullster phil-at-dropthespam.com wrote:
I have just come by a sky dish and notice that there appear to be different positions for the cable inlet. The connection is in like a notched groove, with numbers 1 to 5 above the notches. Effectively the cable connection itself can move into the notch cutouts. These have become worn and the connection has moved - so the questions a What difference does this setting make? Presumably this affects the receipt of signal? If it works, ignore it. My sky box is currently happily working on a 3.99 LNB from LiDl, after the original one failed. It's currently held on by a quasi-cylindrical adjustable ferrous attachment system. (coat hanger.) Works well, and stood up to 70MPH winds without problems. |
#6
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In article , TheScullster
URL:mailto[email protected]. wrote: I have just come by a sky dish and notice that there appear to be different positions for the cable inlet. The connection is in like a notched groove, with numbers 1 to 5 above the notches. Four replies so far and not one of them anywhere near accurate. :-( The setting you describe is the "skew" setting. It is intended to match the X & Y polarisation angles of the satellite. The default setting is position 3, but it is more accurate to peak the signal QUALITY. Ignore the strength, it is of less importance. Incorrect skew will degrade the already marginal performance of the minidish. -- AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk |
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On Sat, 15 Jan 2005 08:41:51 +0000, "Andy Luckman (AJL Electronics)"
strung together this: Four replies so far and not one of them anywhere near accurate. :-( That's the beauty of usenet! -- SJW Please reply to group or use 'usenet' in email subject |
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Andy Luckman (AJL Electronics) wrote:
Four replies so far and not one of them anywhere near accurate. :-( Quite. You beat me to it, but perhaps I can add some background. The setting you describe is the "skew" setting. It is intended to match the X & Y polarisation angles of the satellite. The default setting is position 3, but it is more accurate to peak the signal QUALITY. Ignore the strength, it is of less importance. Yes, it's polarisation skew or offset (not to be confused with the concept of the offset feed). As every schoolgirl knows, satellite TV uses the technique of frequency-interleaved signals on orthogonal polarisations to double the available spectrum. With satellites like the Astra fleet which use plane (linear) polarisation it's most important to rotate the LNB to ensure that signals on the 'unwanted' polarisation are nulled-out, so as to achieve the full available cross-polar rejection performance. With a traditional round clamp type of LNB mount you really need a spectrum analyser to do this. Look at the LNB output and look in the gap between two transponders - the best place to see the unwanted cross-polarised signals - and rotate the LNB to minimise them. To de-skill the installation process, and simplify the test equipment required, Sky digital uses a click-stop approach to this skew adjustment on the mini-dish. The correct setting is no. 3 for the great majority of the UK. If you are in Eire, Devon, Cornwall or Pembrokeshire use no. 2. For NE Scotland - Aberdeen, Inverness, Orkneys and Shetlands - use no. 4. For this to work it's most important that the dish is mounted with its major axis truly horizontal, to which end the more recently manufactured dishes have a built-in spirit level. Incorrect skew will degrade the already marginal performance of the minidish. True, although the margin is not actually that bad if the dish is correctly installed. Most of the problems in practice seem to relate to bad installation, or microwave interference from certain illegal radar jamming devices. -- Andy |
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