Definition of LNB Skewand LNB clockmethodology .

This article will be very useful for
satellite dish installation beginners. We
have all been hearing about stuff like;
tweak the lnb to 3.0clock, 9.0clocl,
5.0.clock or what any of the sort. In
this article, you will learn the basics of tweaking an LNBf to suit a particular
satellite.

WHAT IS LNBf SKEW?

 LNB skew can be defined as the
rotational position of the LNB mounted
on a satellite dish. It must be set within
certain limits to reduce the number of
errors received on both vertically and
Horizontally Polarised Transponders. Spectrum analysers are used to set the
skew by professionals installing
Uplink ground stations and sometimes
receiving (or downlink) satellite dishes
if they have the time. So how do
technicians without very expensive spectrum analyzers use?
This is where the term LNB tweaking comes in. You probably have heard
about LNB tweaking in Satellite TV
forums. LNB tweaking is setting the
LNB using the signal meter levels on
your satellite decoder. So how is LNB tweaking done? This is a step by
step process of setting the correct
LNB skew on your satellite dish.
The actual “skew angle” is
dependent on the satellite your
dish is facing and on your location. It is also affected by how much the
installed dish deviates from the
vertical position. In other words, your dish mount pole should be
installed vertically upright. A spirit level
should help you achieve this. A dish
leaning on its side will not yield good
results even if you use the best
available LNB in the market.

 HOW TO ADOPT CLOCK METHODOLOGY IN DISH INSTALLATION

 When installing a satellite dish, you
should position the LNB using the
clock methodology. This method
assumes that the dish is a clock. Now
when standing behind the dish,
assume that the dish is an analogue clock with twelve o’clock at the top
and 3 o’clock on your right and of
course 9 o’clock at the left-hand side.
Take note of the 9 o’clock position,
this is where your LNB cable should
“originate from” The image above shows an LNB set at this position. Take
note of the 9 o’clock position in the
photo above.
The opposite is also true when
standing in front of the dish the same
position should be 3 o’clock. Whatever method you like it’s up to you.
Now set the dish to the satellite you
want using a Satellite finder or
whatever decoder you own. Make
sure you set the dish correctly to get
the maximum signal strengths. LNB tweaking This tutorial is for Ku band frequencies
on an Offset dish but the basics are the
same for C band as well as Prime focus
dishes.  However circular polarized
signals do not require tweaking.
Set your decoder to show the signal strengths of any weak transponder.
Let’s start with a H, horizontally
polarized transponder.
Loosen the Two screws on top of the
LNB holder and rotate the LNB on its
axis. Take note of how the signal quality bar behaves. There must be a
point where the signal disappears
completely even when the dish is
correctly aligned at the correct satellite.
Return the LNB to the original position.
From this position push it backwards away from the satellite dish. The
following image shows the same LNB
pushed forward and closer to the
reflector, case A. The other image, B
shows an LNB pushed all the way
back away from the reflector. Push the LNB forward and rotate the
LNB within the Limits where the
transponder signal quality does not
go to zero. Push it forward again and
rotate the LNB.
When you hit a new high signal quality level, try not to rotate the LNB, but to
push it forth and back on this new
position.
If the dish is correctly aligned at the
satellite then the weak transponder
frequencies will improve gradually until you hit the maximum signal
quality receivable.
Switch to the other polarization, in this
case, V and compare the signal
strengths. You should make sure that
the signal strengths are consistent with each other.
When you hit the highest signal
strength, tighten the screws holding
the LNB.