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

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.

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

"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

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.

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

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

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