satellites properly. Tightening beforehand can dimple the pipe, making it more
difficult to make subtle adjustments in alignment.
Mounting The LNB And Feedhorn
Extreme care should be taken when bolting the LNB to the feedhorn. Do not
touch the probe inside the mouth of the LNB. This probe can be adversely
affected by grease or dirt. Also make sure that the neoprene gasket that goes
between the feedhorn’s flange and the mouth of the LNB is “seated” properly in
the groove provided. Otherwise, moisture can seep into this opening and
disrupt your reception.
The center of the feedhorn must be supported exactly at the focal point of the
dish. The focal distance between the center of the dish and the mouth of the
feedhorn will vary between different models of antennas, depending on
whether the manufacturer has used a deep or shallow dish design. The exact
distance will be provided in the instructions.
There are two fed support styles available, one of which will be supplied with
your antenna. A “button hook” support, sometimes called an LNB tube, is a
single piece of tubing which extends from the center of the dish outward. The
button hook support, which is curved so that it resembles a hook, allows the
feed to be mounted looking back at the center of the dish. Guy wire kits are
available for button hook supports that will provide the additional stability
required for reception of both C- and Ku-band signals. Ku-band signals are
much higher in frequency and there fore are beamed Earthward in much
smaller wave lengths. Consequently, the antenna curvature and location of the
feed for Ku-band reception must be much more precise than what C-band
systems commonly require.
We recommend that you check to that the feed is centered over the dish by
measuring from the lip of the antenna to the edge of the feedhorn’s opening at
four equally spaced intervals around the antenna’s rim. This is especially
important if you are using guy wires to anchor the button hook support. If the
feed is centered, these measurements will all be equal. If they are not equal,
you will have to adjust the tension if the guy wires until the feed is properly
centered.
The second type of feed support uses a multi-legged structure to hold the
feedhorn and LNB (or LNBs for dualband systems). These are made up of
three (“tri-pod”) or four (“quad”) straight, equal length pieces of aluminum or
steel. Quad supports are inherently more stable than button hook supports,
offering better Ku-band reception. When mounted at the recommended
