each end of the coaxial cable. It mates with complementary connectors on the
LNB and indoor receiver. Your local electronic supply house can provide you
with the special tool used to crimp “F” connectors onto the cable, Or you can
purchase standard lengths of cable with the connectors already installed. The
quality of the F connector is important as some cheaper F connectors break
when crimped, providing an additional entry point for moisture as well as a less
reliable connection.
When screwing an F connector onto mating connectors on the back of the
receiver or LNB, you should take care to avoid bending or breaking the cable’s
inner conductor, thereby shorting out the connection. There also are right-
angle F connectors which can be used whenever space limitations prevent a
straight-on connection.
The block 1F signal coming from the LNB is no longer a microwave signal.
That’s why a relatively inexpensive and readily available coaxial cable of small
diameter can be used to carry the signal to the indoor receiver. The type of
cable commonly used in satellite TV installations has a characteristic
impedance rating of 75 ohms. The type of cable used by CB radios and other
two-way radio equipment has a characteristic impedance rating of 50 ohms
and is not suitable for satellite TV use. Be sure that the cable you buy is 75
ohm coax.
There are several different kinds of 75 ohm coaxial cable available. RG-59U
coax can be used to span distances of up to 100 feet. For longer lengths, lower
loss RG-6 or RG-11 are used. Direct burial satellite cable contains one or two
spans of RG-6. Since RG-6 is slightly larger in diameter than RG-59, it also
requires a slightly larger F connector. To span distances of several hundred
feet, special UHF line amplifiers with +10 or + 20 dB gain also may be
necessary to compensate for the amount of signal loss or attenuation that
occurs as the signal passed along the length of cable.
As the block IF frequency range produced by the LNB may extend upwards
towards 2,000 MHz, the losses in most types of 75-ohm coaxial cable is very
high. These losses can be minimized by using high quality coax from a major
manufacturer from Europe or the United States. Some of the cheaper coaxial
cable now manufactured in Asia, for example, does not meet the higher
performance requirements for satellite TV applications.
The power required to operate the LNB is supplied by the receiver and sent to
the LNB via the center conductor of the coax cable. The power stays on even if
the receiver is turned off. This keeps the LNB at a more consistent temperature
and prevents moisture from condensing inside it. Also available: snap-on
