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Section 5-4-2
5-4-2 Step resolution mode
Example of the screen is shown here, the parameters are:
Centre frequency (CF) = 122.5MHz
Display step
= 25kHz
Frequency span
= 8MHz
Start frequency
= 118.5MHz
End frequency
= 126.5MHz
Marker frequency
= 124.35MHz
In the step resolution mode, the frequency
span is determined by the entry of display
step size, which is OPPOSITE to the
spectrum analyser mode where the
display step size is determined by the
entry of frequency span.
Centre frequency (CF)
Press the CENTRE FREQ. key to make
the centre frequency display read-out
appear in reverse contrast. Enter a
desired frequency via the ten-keys
followed by the kHz or MHz key, this is
now the centre frequency. The main dial
of the SDU5600 may also be used to
select a frequency, you must still use the
kHz or MHz key to complete the
frequency entry sequence.
Assuming that communication between
the SDU5600 and the companion
receiver has been correctly established,
the centre frequency of the SDU5600
becomes the receive frequency of the
companion receiver.
Display step (STEP)
Press the SPAN/STEP special key to reverse the contrast of STEP numeric display on the top line of the LCD.
Enter the frequency step size, using the ten-keys followed by the kHz or MHz key to confirm the entry. Once the frequency step has
been entered, the display step will automatically calculate the SPAN and display STEP and SPAN on the top line of the display.
Note: If you select a step size which is too large, the SDU5600 will default to 31.250kHz step with span of 10MHz... and
will produce an error beep (if the beep facility is enabled). If you select a step size which is too small, the SDU5600 will
default to 0.500kHz step with span of 0.160MHz... and will produce an error beep (if the beep facility is enabled).
Special key - CENTRE FREQ.
This hardware special key is a duplicate of the soft key CENTRE FREQ. and has identical action. Either key may be used to the
same effect.
Effective frequency coverage of the companion receiver
The frequency spread (both sides of the centre frequency) must be contained within the frequency coverage of the companion
receiver. If exceeded, correct monitoring will be impossible.
Display frequency bandwidth is obtained by the following formulae:-
In the spectrum analyser mode: CF +/- (Frequency span divided by 2)
In the step resolution mode:
Example of the automatic calculation of frequency span
In the above illustration, the frequency STEP is 25kHz, so the SPAN is calculated by the SDU5600 as:
25kHz x 320 = 8MHz
where 320 is the horizontal x-axis resolution of the LCD.
.
24
CF +/- (Display step x 160)
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