TELE-audiovision - The World’s Largest Digital TV Trade Magazine - page 45

45
03-04/2014 —
TELE-audiovision International —
全球发行量最大的数字电视杂志
serted and the amplifier
turned off. No leakage sig-
nals could be detected.
For the LTE frequency
band, the dipoles are re-
moved and the amplifier is
turned back on. This acti-
vates the 13V at the R&S
EFL210‘s HF connector out-
put. Once again, no trouble-
some leakage signals could
be found. This isn‘t at all sur-
prising considering that our
cabling adheres to certain
directives.
Now the actual test could
start. Leakage signals were
artificially generated so
that there was something
to measure. Our test setup
was actually quite simple:
we merely inserted a small
dipole antenna into the cable
TV port. Sure enough, from
several meters away and
even through a wall we were
able to identify some QAM
transponders very close to
an LTE transponder at 800
MHz (see photos).
With analyzers like the
R&S EFL210 it can be dif-
ficult to compare meas-
urement results from the
spectrum display with other
analyzers. Why? Because
the R&S EFL210 displays the
spectrum in a higher resolu-
tion thus letting you identify
individual carriers within a
transponder. Of course, the
signal strength varies con-
siderably depending on the
content of the transmitted
data.
If you want to be able to
compare different analyzers
side-by-side, you‘d have to
set up all of the parameters
equally, such as, range as
well as RBW and VBW filters.
But it would be difficult to do
this because of the differ-
ences in the settings of each
device. You would also have
to hope for uniform data
transmission.
A far better way to check
the precision of a signal ana-
lyzer like the R&S EFL210 is
to measure a synthetically
created signal with known
parameters. That‘s why we
used a calibrated signal gen-
erator to test the measure-
ment precision of the R&S
EFL210. To that end we gen-
erated a signal at various
frequencies and at different
power levels and measured
it with the R&S EFL210.
It‘s quite impressive to see
how precise the measured
values turned out. Measure-
ments that are off by less
than 1.0 dBm are incredibly
precise and even a sweep
over various frequency
ranges delivered consistent
results, something that real-
ly only can be achieved with
high-quality hardware.
To measure the sweep we
Often though, the source
of the leaks were not the
splitters of the CATV
operators.
used a very simple trick:
the MAX Hold function was
utilized. This feature con-
tinuously shows the highest
measured values and is nor-
mally used, for example, to
perfectly align an antenna.
In this case with an active
MAX Hold function, the spec-
trum registers the „wander-
ing“ power level. You merely
have to wait until it has gone
through the entire spectrum.
Our conclusion regard-
ing measurement precision?
The R&S EFL210 is not just
a simple signal analyzer, it‘s
a fully featured test instru-
ment. If you use this Rohde
& Schwartz unit to make a
measurement, you can be
sure that the measured val-
ues will be absolutely cor-
rect.
Naturally,
Rohde
&
Schwartz also includes the
necessary Windows software
with the EFL210, the R&S EFL
Suite. With this software,
measurement protocols us-
ing the stored Logger files in
the EFL210 can be created.
You can also edit channel
lists and it‘s even possible to
create frequency tables and
so-called Macros.
Specifically, these memory
frequency tables (MEM) to-
gether with these Macros
makes it possible to auto-
matically create measure-
ment protocols whereby the
R&S EFL210 automatically
sets up and measures the
preprogrammed frequen-
cies.
This is an excellent time-
saving way to perform the
same measurement at dif-
ferent points in an installa-
tion. CATV installers would
especially benefit from this
since the frequency ta-
ble from the cable provider
would only need to be pro-
grammed once via Macro.
From that point on, it would
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