Frequency Tuning - Promax 8 plus Manual Del Usuario Y Operador

The following figure shows that when making C/N measurements in the relative
method ( F), it is essential to bear in mind the presence of adjacent channels; otherwise,
the noise could be confused with the signal of another channel.
Figure 21.- Example of digital channels spectrum.
Taking as example the previous figure, if we suppose that for the channels that
appear in the figure it has defined a bandwidth of 8 MHz, in the relative mode of
measurement the PROMAX-8+ will take as value for NOISE FREQ. = 4.5 MHz. Note
that this method can cause erroneous measures in the measurement of the channels
D24 and D25.
For D24 it is advised to configure NOISE FREQ = -4.5 MHz and to verify if the
measurement increases. In case a channel has two adjacent channels (for example
channel D25) it is recommended to select the absolute mode and to assign to the
NOISE FREQ. parameter a frequency corresponding to a free channel (for example
between D26 and D27).
4.2.3.2

Frequency tuning

When in
FREQUENCY operating
pressing the CH-FR [10] key switches
tuning by channel to tuning by
frequency and vice versa. In the tuning by
frequency mode the instrument becomes a
receiver with a resolution of 10 kHz in the 5 to 862
MHz band. In this mode you may tune to any
signal within the band, including leakage pilots,
telephone and communications signals. To change tuning simply press the rotary
selector [9] until the digit you want to change is underlined and then turn the rotary
selector [9]. The channel number will appear to the left of the tuning frequency, as long
as it corresponds to an active channel.
Remark: When switching from frequency to channel, if the tuned frequency does not
correspond to any channel, the PROMAX-8+ will search for the channel
nearest to this frequency and will stay tuned to this channel. This operation
may take a few moments.
Page 26
CHANNEL-
mode,
INSTRUCTION MANUEL. PROMAX-8+
Figure 22.- Frequency tuning.
May 2001