....
l ,
)
CH. 9
----~---- CH. I 0
186
192
--1--~_,..,..__ CH. 11 ---l
CH. II
ADJ
SND Pl X
198
I
I
I
I
204
Figure 2.2 Frequency Spectrums of Channels 9, 10 and 11 Showing
Relationships of Adjacent Channel Interfering Carriers.
In Figure 2.2, the frequency spectrums of
Channels 9, 10 and 11 are shown adjacent to
each other to show the potential interference
problems of adjacent channel signals. The
sound carrier of Channel 9 (191.75 MHz) is
the sound carrier adjacent to Channel 10 as
mentioned previously. The pix carrier
of
Channel 10 (193.25 MHz) is the pix carrier ad-
jacent to Channel 9, as shown on the dotted
portion of the Channel 9 curve which is ex-
tended into the Channel 10 spectrum.
The channel spectrum for each of the three
channels shown is represented as it would
appear after having passed through the selec-
tivity of the television receiver IF stages.
Further examination of Figure 2.2 shows that
the sound carrier of Channel 10 is adjacent
to the lower limit of Channel 11 and is re-
ferred to as the Channel 11 adjacent sound
frequency. The Channel 11 pix carrier is also
the Channel 10 adjacent pix carrier. These
frequency relationships apply to all televi-
sion channels adjacent to each other. The
purpose of Figure 2.2 is to show that the fre-
quency spectrum of interest includes not only
the particular channel band width, which
is
6 MHz, but the portions on each side of the
bandpass which include the adjaceni chan-
nel sound carrier on one side and the adja-
cent channel pix carrier on the other side.
This is why a sweep width of 10 MHz or
more is desired for sweep alignment proce-
dures, although the television channel band-
width is only 6 MHz.
The sections following will describe how the
transmitted television signal is processed
through the television receiver and will also
describe how various applications of tuned
circuits are utilized to provide the desired
gain and bandwidth characteristics required
in the various sections of the television re-
ceiver to produce a good black and white
picture or a good color picture.
13
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