Versione HTML di base
■
71
www.TELE-satellite.com —
09-10/2012 —
TELE-satellite International —
全球发行量最大的数字电视杂志
1. The SPAUN VAM 420 NG PAL configured to generated two TV
signals: one with maximum level, the other with minimum level (-10
dB). Note that the signals are over 50 dB above the ground noise.
2. As above, but now the adjacent channels are used.
3. Test card picture generated by VAM 420 NG PAL.
4. An analogue TV channel demodulated by the VAM 420 NG PAL
and displayed by the SPAUN SPAROS meter
fully finished off as all SPAUN
products. It is designed to be
mounted either on a DIN rail
or on a flat surface, like a wall
- either directly or with the
help of the included bracket.
SPAUN even offers a perfect
housing for the VAM 420 NG
PAL: it is called SpaceBox and
is a 19” rack which can acco-
modate either up to 5 or up
to 10 VAM 420 NG PAL units.
The modulator can be cas-
caded with three other iden-
tical units and in such case
you can use a single power
supply unit (SPAUN SNG
12/2000) to power all four
modulators. One VAM 420
NG PAL has two sets of inputs
(video and stereo audio) and
generates two analogue TV
channels. As you can easily
calculate, four such devices
can generate 8 analogue TV
channels. SPAUN includes
a plastic spacer to be used
when mounting the modula-
tors one next to the other on
a DIN rail.
Please mind that it is just
a modulator – so if the input
video signal complies to the
PAL color system, it will not
be changed and we will get
the output in analogue TV in
■
The SpaceBox by SPAUN solves any problems, where to mount
the VAM modules. It can house up to 5 or up to 10 VAM 420 NG PAL
units.
PAL. Should it be SECAM, it
will stay as SECAM. However,
except for the color system,
you should also be aware of
the TV standard that speci-
fies how audio is transmit-
ted. And here we have a few
possibilities: B, G, D, K, I or L
standards. VAM 420 NG PAL
is compatible with all of them.
It will be perfect for feeding
analogue tv sets used in Eu-
rope and many other regions
of the world were signals like
PAL D/K or PAL B/G were
used and sometimes are still
in regular days. What it does
not support are the N and M
standards mostly used in the
Americas.
The VAM 420 NG PAL has
two sets of inputs. You can
see the familiar yellow/white/
red RCA connectors in two
columns located at the top of
the front panel. In the bot-
tom part of the panel, there
are two F connectors. One
of them is the output (where
two TV channels appear) and
the other in the input. You
can connect another VAM
420 NG PAL to the input to
increase the number of ana-
logue channels. Here you
can also feed a coax from a
terrestrial antenna to com-
bine the terrestrial signal
with your own two channels
generated by the VAM 420
NG PAL. Observe the advice
SPAUN gives in the included
brochure with technical in-
structions: when connecting
a terrestrial antenna make
sure you insert an amplifier
between the antenna and the
modulator that has at least
20 dB input/output isolation.
Programming the modu-
lator is pretty simple. Only
three buttons are used: Up,
Down and Enter. Frankly say-
ing, we would prefer if SPAUN
called the last button L/R or
something like that. Its func-
tion is just switching between
the left and right channel. In
the normal mode, you select
the left or right channel by
pressing the Enter button.
The decimal point on the two
digit display moves either to
the left or to the right digit
indicating in this way which
channel is currently chosen.
You use then the Up and
Down buttons to change the
channel number from S03 to
69.
When you press and hold
the Up and Down buttons si-
multaneously for one second,
VAM 420 NG PAL switches to
programming mode. Now you
can use the Down button to
travel down the “menu” and
the Up button to change the
value of the present option.
The options are as follow: TV
system, fine tuning of video
carrier frequency, video/au-
dio ratio (16 or 12 dB), test
pattern generator (on/off),
RF output signal (on/off),
RF level adjustment (from 0
through -10 dB), Audio signal
level (from -6 dB through +6
dB), Audio processing mode
(mono, stereo, dual). When
you are through with all the
settings, you again press and
hold Up and Down buttons
simultaneously and leave
the programming mode. And
that’s all you need to program
and operate this device.
To evaluate the perfor-
mance of the modulator, we
drove it with two analogue
signals taken from two sat-
ellite receivers (video and
stereo audio). We connected
the SPAUN SPAROS meter to
the output of the VAM 420 NG
PAL to observe its frequency
spectrum. As you can see in
our screen shots, the gener-
ated signals were extremely
A similar device as the VAM
420 NG PAL is the above model
VAM 420 NG DVB-T, which has
recently been launuched by
SPAUN. The features are the
same as for the VAM 420 NG
PAL, but instead of an analogue
PAL signal the VAM 420 NG
DVB-T has a COFDM output
signal.