TELE-audiovision - Weltweit größte Digital TV Fachzeitschrift - page 48

TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 03-04/2014
Amateur Radio
76. It happens occasionally that a cus-
tomer complains about intermittent TV
reception. Often the cause is an amateur
radio enthusiast, who is using inadequate
equipment. The picture shows the water-
fall diagram of a transmission done with a
cheap handheld radio, emitting at 145 MHz.
Interestingly, the radio disturbs a nearby
transmission at 148.5 MHz. Notice that the
waterfall diagram shows that transmission,
whenever the radio is not transmitting.
This happens, because the radio has not
so good band pass filters, which produce
second harmonics that are stronger than
expected. This second harmonics is visible
as the first smaller line to the right of the
main signal.
77. This is the spectrum view around the
center frequency of 145 MHz wcith a 20
MHz span. The hand held radio is not trans-
mitting in this picture, thus the transmis-
sion at 148.5 MHz is not being disturbed.
78. See what happens in this picture, when
you use the cheap hand held radio: lots of
harmonics, obfuscating all transmissions
in vicinity. With the R&S EFL210 you can
uncover problems resulting from such
devices very easily and in an affordable
way. Thanks to the included directional
antenna you even get to know where the
transmission is coming from, if the inter-
ferences are within the supported bands of
the R&S EFL-Z100 antenna. Otherwise you
can use the R&S HE-300 antenna, which
covers the whole spectrum from 9 kHz to
7.5 GHz, thanks to its modular design.
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