Amplificatore coassiale – coassiale
La modalità di collegamento è descritta in fig.5.
Il dispositivo deve essere alimentato da una sorgente esterna da 12 a 20V DC* e provvede ad amplificare un segnale
standard proveniente da una telecamera TVCC ed ad amplificarlo in funzione della regolazione del trimmer guadagno
ed enfasi che operano come descritto precedentemente.
English
Description
The AMV3000 (
AV3007
) video amplifier, has been especially conceived for 5-wire video systems.
It is used to improve pictures quality over long distances.
It restores the image colours when the installation extension causes a video signal deterioration.
Its electronic circuit performs several functions, the main one being the amplification of differential video signals. It allows to
strengthen the high-frequencies – which represent colours information – separately from general video signal amplification.
Other functions are:
Differential-to-coax conversion of video signals, and vice versa
Video amplification in coaxial CCTV systems
Technical features
•
Power supply (directly taken from the riser supply)…………………12
−
20Vdc*;
*in case of steady supply it is recommended not to exceed 15Vdc
•
Current consumption…………...…………………………………………..…150mA;
•
Setting range of general amplification gain (In=250mV)……….
−
10dB
÷
10dB;
•
Setting range of high-frequency gain (EMPHASIS In=250mV)…
−
7dB
÷
20dB;
•
Input impedance of
Ain - Bin
differential signal to GND……….2 X 75 Ohm;
•
Coaxial input impedance……………………………………………………. 75Ohm;
•
Differential signal output impedance………………………….. 50Ohm
•
Output impedance on coaxial cable ………………………….. 75Ohm
•
Compatibility with both B/W and colour cameras
Adjustments
The AMV3000 (AV3007) has two amplification trimmers. For optimum picture quality, both of them should be adjusted.
To do so, open both covers, locate the trimmers - which are positioned under the bigger one - and proceed as follows:
•
Device’s general gain
To set the amplifier’s general gain, adjust the rightmost trimmer (see fig. 1).
Rotating it counterclockwise, increases gain. This adjustment is useful to compensate signal losses due to long distances
and poor-quality cables.
(CAUTION: excessive amplification could lead to saturation and image deterioration).
•
High-frequencies gain
This setting allows to boost high frequencies selectively, thus compensating the video signal loss over very long
distances. By turning the leftmost trimmer clockwise (see fig. 1), high frequencies are amplified much more than low
frequencies. This operation improves both B/W and COLOUR vision.
In
B/W systems
, this trimmer adjustment should increase the image sharpness.
In
colour systems
, this trimmer adjustment may increase colour saturation (sometimes it may even restore colours in
pictures that have deteriorated to B/W vision ).
Operation as video amplifier in 5-wire systems
The
AV3007
device has been designed for installation on the riser wires of a standard Bitron Video system. It can be
located in whichever position, although it is not suggested to install it very close to the visitor panel, nor to the monitors.
Therefore, the best device position is normally at midway or at 200m from the visitor panel.
For what concerns power supply, it is taken directly from monitors supply wire (n. 3), that is positioned in the riser.
For a right functioning as differential video amplifier, the device has to be connected as follows (fig. 2):
•
Ain
and
Bin
to be connected to
A
and
B
wires
coming from the video group.
•
Aout
and
Bout
to be connected to
A
and
B
riser wires to the monitor
•
+
and
-
to be connected in parallel to
3
and
1
riser wires
•
LINE-OUT
connected to
LINE-IN
by an external jumper
Operation as signal converter
Thanks to its particular circuit, the
AV3007
device can be used as a video signal converter from coaxial to “2-wire differential
system” and vice versa.
From 2-wire differential system to coaxial cable system (fig3).
In this case signals will be used as follows:
•
Ain
and
Bin
as
inputs
•
COAX-OUT
as
output.
•
+
and
–
to
12 –20 Vdc
This configuration is particularly useful when a standard CCTV monitor is connected over long-distance to a 5-wire video
doorphone system. Obviously, gain and emphasis controls remain functional and need to be adjusted.
From coaxial cable system to 2-wire differential system (fig4).
In this case signals will be used as follows:
•
COAX-IN
as
input
•
Aout
and
Bout
as
outputs
•
+
and
–
to
12 –20Vdc
For the video signal transmission, this configuration allows to use inexpensive twisted-pairs instead of coaxial cable. It
can be used either to send signals from standard CCTV cameras to 5-wire doorphone systems, or for CCTV signal
transmission on twisted-pair in combination with a second AV3000 used as differentia-to-coaxial converter.
In this configuration, gain and emphasis controls are
not
active.
Installation as coaxial cable amplifier
The video amplifier can be used to amplify standard signals on coaxial cables (fig.5).
In this case connect it as follows:
•
coax-in
as
input
•
coax-out
as
output
and jump-connect other signals as follows:
•
Aout
to
Ain
•
Bout
to
Bin
.
•
+
and
–
to
12 –20 V DC
Also in this configuration gain and emphasis controls remain functional and need to be adjusted.
CAUTION
Pag. 6
Pag. 5
