PICO MACOM INC. 12500 Foothill Blvd. • Lakeview Terrace, CA 91342 • (818) 897-0028 • (800) 421-6511 • FAX (818) 834-7197
D E S C R I P T I O N S
Strip amplifiers are devices used to boost the amplitude of individual TV signals derived from
an antenna or converter. The critical specifications used to judge their performance are:
1) Output Power
Measured in volts or dBmv
2) Gain
Measured in dB
3) Automatic Gain Control (AGC)
Measured in dB of dynamic range
4) Input Noise Figure
Measured in dB, the lower the better
5) Gain Selectivity
Similar to filter response
6) Aural Reduction Control
Control of the audio carrier amplitude
1) The Output Power
is the maximum output of
an amplifier before signal distortion. At
maximum power, any further increase in gain
will distort the TV signal. Industry standard
output levels are 2 volt = 66 dBmv and 4 volt =
72 dBmv. One may notice that the output levels
are much higher than the maximum output levels
of modulators and channel processors. This is a
carry over from the early days of MATV where
the amplifiers were "looped" together for a
maximum combined output. Looping is only
acceptable when there are no adjacent modulated
channels.
2) Gain
is a measure of the amount of amplification
available in the strip amplifier. Sufficient gain
should be developed in the amplifier to boost a
low level input to the maximum output power of
the amplifier.
66 dBmv units require 12 dBmv
12 dBmv + 54 dB gain = 66 dBmv output
72 dBmv units require 10 dBmv
10 dBmv + 62 dB gain = 72 dBmv output
3) Automatic Gain Control
is the ability of a strip
amplifier to set the output power independent of
the input level. I like to think of AGC as "gain
in reserve". The simplest way to explain AGC
is with an example.
Assume a strip amplifier has a maximum gain of
54 dB and the output is set to 55 dBmv. The
input to the amplifier is initially 10 dBmv. Only
45 dB (55dBmv - 10dBmv) of the available 54
dB of gain is being used. Nine dB of gain is
presently in reserve. If the input drops to 0
dBmv the output will only drop to 54 dBmv but
all of the gain margin is used.
4) Input Noise Figure
is a specification similar to
LNB temperature. The lower the number the
better the amplifier can produce clean pictures at
low input levels. The Input verses Noise Figure
table lists several input levels and the required
input noise figure required such that the ampli-
fier will not contribute any noise to a 50 dB S/N
input signal.
Given
Required
Input Level
Noise Fig
-6 dBmv ........................... 3 dB
-3 dBmv ........................... 6 dB
0 dBmv ........................... 9 dB
5) Gain Selectivity
is a measure of the amplifi-
ers ability to only amplify the desired channel.
Pico Macom strip amplifiers have sufficient fil-
tering to operate adjacent to modulators or other
strip amplifiers. Bandpass filters are required
only under strong channel “skip” conditions or
when alternate channels are significantly stron-
ger than the channel to be amplified. The pur-
pose of the filter is to clear the adjacent channel
so that a modulated signal or a converted signal
may be inserted.
6) Aural Carrier Reduction
Reducing the am-
plitude of the audio carrier allows the distribu-
tion system to operate at a higher level. More of
the amplifiers energy can be used to increase the
video carrier level. Since NTSC audio is fre-
quency modulated, the audio quality is main-
tained for audio carrier levels as low as -17 dB
below the video carrier. Standard off-air broad-
casters set the transmitted audio carrier only 5
dB below the video carrier.
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S P E C I F I C A T I O N D E F I N I T I O N S
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