AOR SDU5600 Spectrum Display Unit Operating Manual

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Channel scope mode
The previous page explains the receive frequency operation in the spectrum analyser mode and step
resolution mode. The channel scope mode differs since it does not use the centre frequency (CF),
instead the receive frequency equals the marker position:
Channel Scope Mode - Receive Frequency = Receive Marker position
In addition, by use of the marker receive key MK.F you can track and select any active receive
frequency for monitoring within the frequency band presently shown on the screen.
FUNC + 3 selects Channel Scope mode
The currently selected centre frequency will become the new START frequency, the CHANNEL
STEP is default 100kHz, the bandwidth is initially selected as 5MHz. You can change the start
frequency, channel step and end frequency... or just press ENT three times to accept the current
defaults.
Use the SDU5600 main dial to select a peak on the display to indicate the presence of an active
channel, press MK.F to receive the new frequency. As you move the main dial again, you will note
that a new yellow-outline marker appears at the current position on the display, this is the receive
marker. You can toggle the display line to confirm RECEIVE MARKER frequency or MARKER
frequency position using the key sequence FUNC + MK.F (MK.R). When RECEIVE MARKER is
selected, a green dot ˜ is displayed on the LCD.
The channel scope mode cannot be selected when the companion receiver has been selected as
Other(10M) or Other(45M), or the communications between the SDU5600 and the companion
receiver has been disrupted.
The example of the channel scope mode here displays the following parameters:
Receive marker = 81.3MHz
Receive frequency = 81.3MHz
Marker position = 82.5MHz
Start frequency = 79.0MHz
Channel step =  25kHz
End frequency = 83.0MHz
Receive marker [MK.F] key
In the spectrum analyser mode and step resolution mode press the MK.F key to swap the marker frequency for the
centre frequency (CF). This is convenient if you wish to listen in the marker frequency immediately.
Section 5-2-2  
						

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5-3 Setup of the monitoring mode
The SDU5600 is designed to provide 3 different monitoring modes such as the spectrum analyser
mode, step resolution mode and channel scope mode. Choosing the most appropriate monitoring
mode for your specific requirements is important to maximise performance and efficiency of the
SDU5600.
Method of selecting each monitoring mode:
  Spectrum analyser mode Press FUNC + 1  (SPECT)
  Step resolution mode Press FUNC + 2  (STEP)
  Channel scope mode Press FUNC + 3  (CHANL)
The 1, 2 and 3 keys are allocated with the 
‘second
function’. The selected mode is displayed on the second
line from the top-right side of the LCD as OP.MODE
Each mode has unique features.
Spectrum analyser mode  (SPECT)
This is most suited for general listening and to hunt for non specific signals or noise,
by sweeping across the defined range of spectrum (up to a bandwidth of 10MHz).
Step resolution mode  (StepReso)
This is most suited to monitor specific signals across a known relatively wide defined
band where signals are allocated with a certain stepping size, for example VHF
airband. The horizontal x-axis of the LCD has a resolution of 320 dots, each dot
represents one step, so there are a total of 320 steps.
Channel scope mode  (Channel)
This is most suited to monitor a
known narrow channelised band of
frequencies such as the VHF or UHF
amateur band. Channel scope mode
can emulate almost a real-time band
scope between the start and end
frequency with defined stepping size.
When the companion
receiver has been selected
as 
Other the channel scope
mode is disabled.
Section 5-3  
						

							23
5-4  Basic setup for each monitoring mode
This section will explain how each monitoring mode has to be set up.
5-4-1  Spectrum analyser mode
Example of the screen is shown here, the
parameters are as follows:
Centre frequency (CF) =  122.5MHz
Frequency span =  10.0MHz
Start frequency =  117.5MHz
End frequency = 127.5MHz
Marker frequency =  123.5MHz
Operating step =  31.25kHz
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.
Frequency span  (SPAN)
Press the SPAN/STEP 
special key to reverse the contrast of SPAN numeric display on the top line of the LCD.
Enter the frequency span (range / bandwidth), over which you wish to monitor using the ten-keys followed by the kHz or MHz key
to confirm the entry. Once the frequency span has been entered the display step will be automatically calculated and displayed as
STEP on the top line of the LCD to the right of the SPAN.
Start frequency and end frequency
The START and END frequency can be entered in the same manner as the centre frequency entry using the assigned soft keys,
ten-keys and ENT key.  The main dial is not valid for the entry.
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.
Enter key  MHz/kHz
SDU5600 has TWO ENTER KEYS, either may be used to complete key sequences.  When inputting frequencies, you may use kHz
or MHz format. For example, ten-MegaHertz may be entered as:
     1 0 MHz
or
     1 0 0 0 0 kHz
Example of the automatic calculation of the display step
In the above illustration, the frequency SPAN is 10MHz, so the STEP (incremental resolution of the horizontal x-axis) is automatically
calculated as:
10MHz divided by 320 = 31.25kHz
Section 5-4, 5-4-1 
						

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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: CF +/- (Display step x 160)
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.
.
Section 5-4-2  
						

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5-4-3  Channel scope mode
Example of the screen is shown here, the parameters are:
Start frequency =  118.0MHz
Step frequency =  25kHz
End frequency =  122.00MHz
Frequency span =  4MHz
Marker frequency =  121.8MHz
Receive marker =  119.7MHz
Unlike the spectrum analyser mode or step resolution
mode there is no centre frequency (CF) in the channel
scope mode.
Start frequency (Ch.START)
Press the Ch.START key to make the start frequency
read-out  display appear in reverse contrast. Enter a
desired frequency using the ten-keys, which is the
lowest of the frequency spread you wish to monitor
(start frequency), followed by ENT to confirm.
Step frequency (Ch. STEP)
Press the Ch.STEP key to make the step frequency
display red-out appear in reverse contrast. Enter the
desired step frequency of your choice using the ten-
keys followed by ENT to confirm.
End frequency (Ch.END)
Press the Ch.END key to make the end frequency display read-out appear in reverse contrast. Enter a frequency, using the ten-keys,
which is the highest of the frequency spread you wish to monitor (end frequency), followed by ENT to confirm.
Receive frequency (RX.FREQ)
When the channel scope mode is activated, monitoring begins on the start frequency.  Rotate the main dial of the SDU5600 to move
the marker onto the signal of your interest, and press the MK.F key.  The yellow receive marker moves to the nominated position and
the companion receiver monitors the wanted frequency.  As the main dial of the SDU5600 is rotated, the white marker moves and the
yellow receive marker is left in position to signify the current active receive frequency.  To select a new frequency to monitor, simply
press the MK.F key.
Note: The end frequency (Ch.END) is confined by the formulae:
(CH.START) + [ (Ch.STEP) x 160 ]
or
(CH.START) + 5MHz
For this reason, if you do not enter an END frequency, the SDU5600 will automatically select an appropriate end point.
Invalid entry for the end frequency will be alerted with a beep (if the feature is enabled), and the closest possible valid
frequency will be automatically chosen by the SDU5600.  Similarly, any invalid entry of frequency will be alerted with the
beep (if the feature is enabled), and will be automatically adjusted to the nearest possible frequency by the SDU5600.
Section 5-4-3  
						

							26
5-4-4  Common features shared by different monitoring
modes
Input sensitivity (AMPLITUDE)
This feature refers to the setup of the input
sensitivity level of the SDU5600 which is
adjusted by the internal amplifier of the
SDU5600. There are 4 different levels of input
sensitivity between 0dBm and -30dBm in 10dB
steps.
Press the AMPLITUDE special key to make the
reference level display appear in reverse contrast.
Enter the required sensitivity level via the
ten-keys or main dial, followed by ENT.
For example, If -20dBm is required press
AMPLITUDE 2 MHz.  You can ignore trailing
zeros ‘0’ following 2 in this instance.
Any invalid entry will be alerted with the
beep, and the nearest possible value will be
automatically selected instead.
The resulting displayed signal wave on the LCD
is affected by combinations of various factors
such as input sensitivity of the SDU5600,
attenuator position and AGC setting (where
applicable) of the companion receiver. Higher
input sensitivity does not always provide the best
results. It is also possible to produce distorted
signals due to saturation to / from the companion
receiver, this may lead to a raised noise floor of
the SDU5600 or spurs.
Significance of the input sensitivity
(reference level)
The two plots shown here show the results from monitoring the same signal at 80.0MHz WFM but using different
input sensitivity settings.
The plot on top was produced with the input sensitivity of -30dBm, the input sensitivity is too high, which results in
unstable operation within the RF amplifier of the SDU5600. This has produced some ghost signals (images)
separated at regular intervals.
The bottom plot was produced with the input sensitivity of -20dBm. Optimum results are obtained due to correctly
selected input sensitivity.
It is important to select the input sensitivity most appropriately to ensure best results.
The AR5000 series receivers and RFU5600 feature AGC level adjustment, however AGC level cannot be adjusted
remotely from the SDU5600.
Effective use of the attenuator of the companion receiver will be required to prevent saturation of received
signal particularly when an external aerial is used.
Section 5-4-4  
						

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Resolution band width (RBW)
The SDU5600 provides four
selectable RBW bandwidths
which are 4kHz, 32kHz, 64kHz
and 128kHz.
Press the RBW key to make the
RBW display appear in reverse
contrast. Rotate the main dial to
select the desired value followed
by MHz or kHz to complete the
selection sequence.
The two plots here show the
results from monitoring the same
signal (80MHz WFM) but using
4kHz and 128kHz RBW
bandwidths respectively.
With the narrower RBW, the finer
signal activity can be observed.
With the wider RBW bandwidth
the resolution becomes coarse
but it can be more suited for
signals with wide bandwidth such
as FM broadcast signal.
The RBW should be chosen
as appropriate for different
monitoring requirements.
As the SDU5600 employs
modern DSP/FFT techniques,
there is no difference in screen
update speed irrespective of
which RBW has been selected.
However, selection of RBW may
affect the displayed signal strength.
When a signal is displayed which is much wider in bandwidth than the currently selected RBW filter,
there will be some inaccuracy in the signal strength displayed.  This is because the wider signal will
loose some of its energy after passing through the narrower RBW filter. The same signal may
produce a higher signal strength on the LCD display if it has passed through (more appropriately
selected) wider RBW filter.
Section 5-4-4 
						

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5-5 Marker
The SDU5600 has a marker facility. The
marker is often used to obtain the reading
of the frequency of interest. In addition to
the instantaneous reading,  it provides the
peak detection and continuous peak
detection.
Press FUNC + MK.F to place the
SDU5600 in to marker mode operation.
Instantaneous readingMarker
Peak detectionPeak
Continuous peak detectionC-Peak
Instantaneous reading (Marker)
This feature is useful for many
applications. The marker can be moved
sideways by rotating the main dial.
The LCD displays the frequency and
signal strength reading where the marker
is positioned.
Peak detection (Peak)
This feature is used to detect the most
powerful signal while sweeping the
frequency spread.
Press the PEAK key, which in turn
requests a trigger level, you need to
specify what level is required. Enter the
trigger level via the ten-keys. Only signals
which are stronger than the trigger level
you specified will then be subject to the
peak detection.
The marker will be forced to the position
of the strongest signal detected and end
its sweep sequence.
The trigger level is selectable from
-90dBm to 0dBm in 1dBm steps.
Entry is via the ten-keys and the sequence
is confirmed by ENT
Section 5-5 
						

							29
Continuous peak detection (C-Peak)
This facility is designed to continue the peak signal detection process one sweep after another.
Press the C-Peak key to activate the facility. There is no trigger level setup in the process.
To return to the instantaneous
reading either from the peak
detection mode or continuous
peak detection mode press the
CLR key... depending on the
operating configurations a multiple
press of CLR may be required.
Marker receiver (MK.F)
This facility is designed to force the
companion receiver to receive the
signal where the marker is
positioned on the screen. There
are slight variations in functionality
monitoring mode-by-mode.
MK-CF
In the 
spectrum analyser mode and step resolution mode the key it works as MK > CF(marker to centre frequency) which forces the marker frequency to become the centre frequency.
MK-RF
In the channel scope mode the key works as 
MK > RF (marker to receive frequency) where the
companion receiver will receive the marker frequency. The start frequency, channel step and end
frequency are unaffected, so will continue monitoring in the channel scope mode as configured.
  MK.F key functions
Spectrum analyser mode
Step resolution mode
Channel scope mode
When the continuous peak detection is being used in the channel scope mode, the marker will
automatically move to the strongest signal detected in the process of sweep. Press the MK.F key to
automatically tune the companion receiver to the strongest signal instantly, so that you can monitor
the active frequency.
Section 5-5 
						

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5-6 Calculation facility
Maximum value hold (MAX)
Press the FUNC +7 keys to activate this
facility, the legend MAX will be displayed
on the graticule section of the LCD.
Press the CLR key to exit from max hold.
Without the MAX feature being used, each
new sweep across the frequency spread
will renew the signal activities over and
over. However, with the MAX feature in
use each sweep will be retained as data is
built-up until the process ends. This is
particularly useful to detect intermittent
signals which come and go over a period
of time.
Averaged value (AVR)
Press the FUNC + 8 keys to activate this
facility, the legend AV R will be displayed
on the graticule section of the LCD.
You are required to enter a sampling cycle
between 2 and 31 to produce averaged
results.
Press the CLR key to exit.
This facility is designed to provide the plot
pattern which has been obtained by
averaging the detected signals repeated
over the number of times in the sampling
cycle.  This facility enables the SDU5600
to produce a stable signal pattern even if
each signal is fluctuating in signal strength.
Median (MED)
Press the FUNC + 9 keys to activate this facility, the legend MED will be displayed on the graticule
section of the LCD.   The plot is designed to provide the signal pattern based over a sampling cycle
of between 2 and 4 and is useful to plot impulse noise. The sampling cycle can be entered via the
ten-keys followed by ENT Press the CLR to exit.
Theory of median filter
AVR N = 31
FIRST SWEEP PLOT AS THE SWEEP PROGRESSES
SECOND  SWEEP (1 + 2) / 2 = A
THIRD SWEEP (1 + 2 + 3) / 3 = B
:::
30TH  SWEEP (1 + 2 + 3 + ..... 30) / 30 = A1
31ST  SWEEP (1 + 2 + 3 + ..... 30 + 31) / 31 = B1
32ND  SWEEP ((B1 X 31 / 32) + 32) / 32
Section 5-6