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1 -12/2013 —
TELE-audiovision International —
全球发行量最大的数字电视杂志
Source is a portable unit with
built-in rechargeable batter-
ies, it was easy to transport
it to the switch box and then
put it to work. It was simply
connected to a Netbook and
operated without a power
connection.
The built-in rechargeable
batteries in the signal gen-
erator let you operate with a
laptop for longer periods of
time without a power con-
nection since the signal gen-
erator won’t suck the laptop
battery dry if you don’t use
both of the USB connections
on the Handheld Satcom
Test Source (the second USB
connection serves exclusive-
ly to recharge the battery).
The measurement of the
complete spectrum with
these parameters needed
about five minutes. Dur-
ing this time you could con-
fidently
focus
your attention on
something else
because if the
test is longer, the
measur ement s
would simply be repeated
continuously.
The results of these mea-
surements show that there‘s
a signal attenuation of 10
dB to 15 dB through the
signal distribution system.
These are overall good val-
ues considering that there’s
over 20 meters of cable, a
multiswitch, an antenna jack
and some more cable be-
tween the Handheld Satcom
Test Source and the Deviser
S7000.
But this measurement
does point out a rather an-
noying aspect of this setup:
the signal attenuation is not
constant across the entire
1. Testing the DVB-T USB dongle with SDR# at 50
MHz. The signal is clean and correctly tuned on the
supposed frequency.
2. Same test, but now on 120 MHz. This frequency
band is used for air control communications and it is
good to see that the DVB-T USB dongle behaves very
well here.
3. At 180 MHz the reception is acceptable, albeit
the gain is lower. The indicated dB value is just a
reference as the RTL2832U chip and the FC0012 tuner
have automatic gain control activated.
4. Unfortunately my DVB-T USB dongle has the FC0012
tuner instead of the much better E4000 one. The result
is a total deafness at 950 MHz.
5. As expected, no signal at 1200 MHz, either.
6. At 118 MHz frequent radio communications between
pilot and tower can be heard as the test centre is
located near the local airport. Using the Handheld
Satcom Test Source I can be sure that my DVB-T USB
dongle is capable of tuning and demodulating this
frequency.
7. I did not have to wait long to get to hear a pilot
reporting to the tower. Notice the small red line
at 118.000 MHz in the waterfall graph. It suddenly
appears with the communication and lasts only a few
seconds. This kind of air traffic communication is
naturally modulated in AM and it is incredible that a
DVB-T USB receiver for less than 20 Euro can actually
be used as a SDR radio scanner to receive such
communications.
frequency range, but rather,
some frequency segments
are more strongly attenu-
ated than others.
There‘s no question: the
WORK Microwave Handheld
Satcom Test Source makes
it possible for an installer
to check out an installation
before the actual signals are
sent through it while at the
same time the quality of the
system can be confidently
verified using a certified ref-
erence signal.
The emphasis here is on
“certified” and “reference”:
with the Handheld Satcom
Test Source there are no
longer any discussions about
error tolerances.
Testing
an SDR Receiver
We even stumbled across
an unusual application for
the Handheld Satcom Test
Source: the DVB-T COFDM
demodulator built in to many
USB DVB-T receivers, the
Realtek RTL2832U, can also
be used for radio reception
because this chip makes
available the raw I/Q sam-
ples.
The thought here was to
be able to demodulate DAB,
