The signal level for each frequency is displayed vertically, the lower frequencies
appearing at the left of the screen and the higher ones at the right. The amplitude of the
lobes is calibrated. In the example in previous figure the noise level is at around 20
dBµV and the lobe with the highest signal level (second from the right) is at 69 dBµV.
The frequency range displayed (called span from hereon) can also be altered
using the Spectrum Analyser mode functions menu.
Also, it is possible to define the detection mode (peak or average) by means of
the Detection Mode function, it affects the form in which the spectrum appears in
screen. The Peak mode is used for the detection of analogue modulations whereas the
average mode is more suitable to detect the digital modulations.
A vertical broken line, called marker, appears on the spectrum display to identify
the tuned frequency.
One of the applications of the PROLINK-4/4C
Analyser is in the search for the best orientation and position of the receiving antenna.
This is particularly important in UHF. Because such frequencies are involved, with
wavelengths ranging from 35 cm to 65 cm, if the antenna is shifted only a few
centimetres, the relationship between the picture, chrominance and sound carrier
frequencies change, affecting the quality of the picture in the receiver.
If there is an excess of sound carrier, tearing or 'moiré' may appear on the screen
due to the frequency beats between the sound, chrominance and the picture
frequencies.
If there is a chrominance carrier defect, then the television colour amplifier must
function at maximum gain, which could result in noise appearing all over the television
screen with points of colour that disappear when the saturation control is reduced; in an
extreme case, loss of colour may occur.
4.10.1 Spectrum Analyser Mode Functions Menu
In the Spectrum Analyser operation mode, pressing the rotary selector [4] leads
you to the next functions menu.
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USER'S MANUAL. PROLINK-4/4C
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06/2005