Carver TX-11b Manual page 16

antenna, can provide a quality signal for the TX-11 b. Even in "fringe
areas" where good reception is normally a real problem. Be sure any
mast or tower set-up is properly secured with guy wire supports (if
needed), and installed where it can't fall into power lines, the
neighbor's greenhouse, or whatever.
Cable
When we talk about cable, we mean a master antenna system
supplying high quality TV and FM signals to individual homes (or
"subscribers"). The signals are sent via a distribution network of wires
and line amplifiers. The wire, or cable portion of the system, can be
likened to a telephone distribution set-up. The line amplifiers are used
to boost signals at certain intervals in the lines, much like using an
antenna preamp with long feedlines in your own antenna system.
Originally, community cable television (CATV) was a response to the
problems of poor or nonexistant reception of TV signals broadcast
"clear air." These problems could be caused by distance, terrain, or
even just remote locations (out of range, or fringe area reception).
The cable company chooses a high hilltop or other location where
they can obtain the best line-of-sight to the area's transmitting towers.
This site is known in cable parlance as the "head end." This is where
high-gain antennas and amplifiers are used to receive distant, weak,
or otherwise unreceivable signals. The signals are passed on to line
transmitters, then to the distribution part of the cable system.
At your home, signals from the cable in the street are fed to your TV
set. If you want FM as well as TV, the signals are split with one set
going to the TV, the other to your TX-11 b. Of course, you can be
connected to just receive FM signals, without the video hook-up. An
FM feed may use a special filter to remove TV interference, or to
prevent you from illegally receiving FM signals from a single TV feed,
an FM trap might be installed at the street. When the cable people
connect your TX-11 b to the system, any necessary filters are installed,
any traps are removed from the line. This brings up something else
again: it's not legal to tap into, or hook a commercial cable up yourself.
It must be done by the cable company.
As mentioned earler in this manual, feedlines for cable TV are all 75 fl
coaxial cable, so connections can be made directly to the TX-11 b's
75 ft antenna input. However, the usual procedure is for the cable
company installer to connect a tuner with a matching transformer (75
ft to 300 ft) to its 300 ft inputs. As we suggested, ask the installer if
it would be possible to use the TX-11 b's 75 ft input.
The benefits of using a commercial cable to supply high quality FM
stereo signals for the TX-11 b are many. For example, you don't have
to worry about the cost and effort of installing a good outdoor antenna.
You don't have to worry about the performance of such a system after
all that work, either. As a rule, cable companies have a one-time
installation charge, then a monthly fee. The cost of cable service can
depend on many factors, and varies from system to system. Costs
will run higher for a commercial cable feed for both TV and FM service,
less for FM only.
Other than opening up a new world for enjoyment of FM programming,
commercial cable can open a new world of audio for your TV set. Many
cable systems program premium movie/film services with spectacular
stereo soundtracks. The video portion (with standard audio carrier)
is broadcast on the cable for the TV set. A separate stereo soundtrack
is broadcast in the FM band. The TX-11 b receives these signals and
turns your living room into a real theater or concert hall. You not only
see great artists performing your favorite music, but hear it like you
were there. This set-up frees your TV from its burden of having a tiny,
limited-response, internal audio amp and speaker.
AM Antennas
The Motorola CQUAM™ AM stereo system requires a stronger and
cleaner signal to take full advantage of the benefits of AM stereo. Two
AM antennas are included with your TX-11 b: a long wire antenna and
a loop antenna. We have detailed the benefits of each type to help
you select the best antenna for your environment.
AM Wire Antenna
The long wire antenna is, under most circumstances, the preferred
antenna. It is able to receive signals from farther away and will receive
normally distant signals much stronger than the small loop antenna.
This wire antenna is also more effective for eliminating noises that
occur in in the atmosphere that is at a distance from the tuner. The
long wire orientation is not particularly critical. Since this antenna is
used for maximum sensitivity, if you live very close to a strong
transmitter you may overload the front end of your tuner with this
antenna and will want to try the loop antenna.
AM Loop Antenna
There are certain conditions in which the loop antenna works best. It
has better noise rejection for locally generated noise - noises that
are generated close to the tuner and may sound like buzzes or hum.
It is able to reduce these noises for two reasons: 1) This antenna is
directional, and 2) it has a lower driving impedance than the wire, so
it tends to short circuit this kind of interference readily.
The loop antenna picks up the signal at right angle to an axis passed
through the loop. If you want to pick up a radio station that is due north,
orient an axis that passes through the loop at right angles to north. If
you were holding this antenna as if it were a gun, you would point it
at the station. Again, the loop antenna is for maximum rejection of
locally generated interference.
Ultimate AM Antenna
For those of you who would like to take the time to build the ultimate
AM antenna, we offer the plans that follow. This antenna incorporates
the benefits of both the wire and the small loop. It will have the noise
reduction capability of the small loop for locally generated noise, the
noise reduction capability of the wire for atmospherically generated
noise, it will be extremely sensitive, and it will be very directional.
This antenna is basically a home-built loop whose area is measured
in square feet rather than square inches. To build this antenna:
1) Construct a wood cross frame that measures 12" from point to
16
I