N4L PSM1700 User manual

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PSM/SLM1700 - feature guide
Introduction
The modified PSM1700 has been designed to provide SLM functionality plus enhanced generator
functions and scope modes that can be achieved with existing PSM hardware.
POWER and HARMONIC modes included in the standard PSM instrument have been replaced
with SLM and SCOPE modes with corresponding menu options presented by pressing the
respective key.
In the following pages, we illustrate the basic operating principle of these new modes using a ‘dual
sinewave’ mode in the output menu to generate a composite signal of two frequency components.
Before proceeding with the examples given below, CH1 and CH2 should be connected to the
generator output which can be done using a BNC T-piece and two BCN to BNC cables or the BNC
output lead with clips and scope leads for each channel that are provided with the instrument.
Quick start
The SLM function in the SLM1700 will
identify either the single largest or the two
largest signals within a specified
frequency range.
Here we will focus on the ‘dual scan’ SLM
mode and to enable the simulation of a
dual signal environment, the generator
has been equipped with a ‘dual sinewave’
option.
From the OUT menu, use the ▼ a nd ►
keys to select the dual sinewave mode.
In this mode, the generator output will
combine two sinewave components that
can be controlled in both frequency and
amplitude.
Numeric values are changed by placing
the edit box over the item to be changed,
entering numbers from the keypad plus an
engineering extension if required then
‘Enter’.
Here, a 1kHz repetition frequency is
entered with 9 cycles for sinewave 1 and
12 cycles for sinewave 2 resulting in a
composite signal comprising 9kHz and
12kHz components.
Then, select output and switch to ‘on’.

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Pressing the SCOPE button, the output
signal can be seen and the scope mode
will have default ‘auto’ trigger. Pressing
the SCOPE button again, scope options
are presented. From here, the trigger
option can be changed to ‘normal’ and
after pressing the home key twice, the
scope screen will return with a cursor
mark (>) on the left axis. Using the ▲ and
▼ keys, the trigger level can be set to the
peak of modulation and a stable waveform
should be visible. Timebase can be
adjusted using the ◄ and ► keys.
Pressing the GRAPH button, CH1, CH2 or
CH1 and CH2 display can be selected.
While this example has the same signal
on both channels, both channels are
independent and can
used to show
different signals.
Now, press the SWEEP button to present
the sweep options.
Set the vales as shown here.
Note: While ‘log’ and ‘linear’ step options
are available, only log steps are presently
implemented

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Now press the SLM button to enter the
SLM mode and again to see the default
mode settings as shown here.
Pressing the SLM button again or the
HOME butto
n will return to the SLM
screen.
Pressing the START key will now start a
sweep with the steps and frequency range
that were entered in the frequency sweep
menu.
Within the resolution of the sweep steps,
the two largest signal components will be
marked with cursors and quantified in the
left axes.
Having identified the largest signals, the
frequency 1 and frequency 2 values within
the SLM option screen will be updated.
In this case, it is clear that the sweep is
successful and we can go straight to an
SLM scan.
If the desired signals are not detected, the
frequency range, number of sweep steps
or selectivity can be adjusted.

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Here, the increased frequency resolution
resulting from a 100 step sweep rather
than the default 32 step sweep is
illustrated.
After completing a successful sweep,
press the ENTER key to begin an
automatic SLM scan.
The SLM1700 will automatically scan
around the identified signal frequencies
with smaller sweep steps and increasing
selectivity.
On completion of the scan, measurements
will continue and using the ▲ and ▼ keys,
the generator signal level can be changed
to illustrate real time measurements of two
frequency locked voltages.
Using the ► and ◄keys, frequency 1 can
be manually stepped up or down.
Manual control of frequency 2 can be
achieved after selecting frequency 2 under
the ‘frequency step’ option of the SLM
menu.

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By selecting a frequency sweep range that
is reasonab
ly close to the anticipated
signal points, increased sensitiv
ity is
achieved and harmonic lobes associated
with harmonic analysis and broad
selectivity can be seen.
Note: The SLM1700 is presently
configured to expect a difference of at
least 15% between
two frequency
components. So, two frequency
components of say 8kHz and 9kHz would
not be differentiated.
Illustration of a classic wide selectivity
DFT sweep can be illustrated by using
100Hz selectivity and a narrow frequency
sweep around the target signal.
dBm values shown in the SLM display are
based upon a selectable ‘reference
impedance’ option in the system option
screen (SYS key).
The impedances are implemented
mathematically
rather than physical
impedance change and the options
presently implemented are 50, 75 or 600
Ohms.