This is a workaround to
get a spectrum-analyzer tool for people like me who run 32-bit PC
(real spectrum-analyzer need 64-bit systems).
The idea is to capture
and store the SDR spectrograms (the waterfall) at fixed time intervals
while the SDR is recording. When the recording time is elapsed, you
may browse the saved screenshots and once you detect a certain signal
you can access directly to it through the I/Q recording using the
timestamp of that signal (which is printed in the waterfall). My test are with
SDR-Console v2.3 and 20/20 v2.2 software, the latter is the programmable
screen-capture tool.
setting the 20/20 v2.2 software
First of all, 20/20 v2.2
need to be executed as windows-95 compatible (Fig. 1)
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| Fig. 1 |
Run 20/20 v2.2 and hit
files-> preferences to set
the output directory and file, auto save, image format, and
auto-increment as in Fig. 2 then set the capture-parameters paying
attention to the Timed Options, Capture Target and
Capture To (Fig. 3).
The
most important value is the Timed Options:
the Time Capure shall
match the time needed to fill the SDR waterfall (better few second
less so to get a little overlapping between two consecutive
captures). In my case I preferred 60 seconds and then I will have 60
screen-shots/hour. Hit Ok
and 20/20 starts.
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| Fig. 2 |
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| Fig. 3 |
setting
the SDR software (SDR-Console v2.3)
The most important settings are intended to adjust the waterfall
speed and height. In my opinion, 10 lines/second is the better
resolution value, allowing to fit the waterfall in about 60 seconds
(Fig. 4). Remeber that the time needed to fit the waterfall shall
match the Time Capture value in Fig. 3! Note also that you
have to set Add timestamp option in SDR-Console (Figs 5).
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| Fig. 4 |
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| Fig. 5 |
Once found the best values and window heigth, you may start the
recorder after setting the duration of the recording (Fig. 6).
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| Fig. 6 |
Now
you may go for a walk or at your job, stay with your partner, have a
fresh beer or simply go to sleep: 20/20 & SDR recorder will do
the job for you, once recording finished you will have the chance to
analyze the stored waterfall screen-shots.
Analyzing
the spectrum
Remember
to stop 20/20: it run in background, saving screen-shots at the
scheduled time. Browse
the directory where 20/20 stores the screen-shots, as indicated in
Auto Save (Fig. 1), you will see something like Fig. 7
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| Fig. 7 |
Images
can be seen one at time, back or foward, using the Windows images
viewer or some other similar tool. This way you may carefully examine
every single “capture” using also the zoomer. At the same time,
run SDR-Console and playback the recordered I/Q file (Fig. 8) keeping
it paused. Minimize the SDR-Console window.
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| Fig. 8 |
When you see an interesting signal (unknown or maybe known by its shape) in a certain stored screen-shot, you
have to write down the related timestamp and go to the SDR-Console
window. Now, working with the playback navigator you have
simply to access to the time slot which is related to the seen signal
and play it, i.e. as shown in Figs. 9,11 (the being analyzed screen-shots) and 10,12
(playing the needed time slots from the I/Q file). Pay attention to
the different time-format in the captured screen-shots and I/Q file!
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| Fig. 9 |
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| Fig. 10 |
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| Fig. 11 |
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| Fig. 12 |
20/20
v2.2 can be downloaded from:
(googling
for it ...you may turn up an XXX site).
A better tool for screen capture is "autoscreen" (Fig. 13)
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| Fig. 13 |
You can download the software from:
https://sourceforge.net/projects/autoscreen/
ake screenshots automatically while you work and play! You can either
use the interface or run it from a command line. The application
("autoscreen.exe") is a self-contained executable (which means there's
no installation required) and sits in the system tray while it takes
screenshots in the background without prompts or annoying pop-up
messages.
The executable is only 209 KB in size so it can fit on a small (or a very old) USB thumb drive.
You can schedule to have screenshots taken every hour, minute, second,
or millisecond. You can also specify what days the scheduled screenshots
should be taken. The calendar enables you to see what days screenshots
were taken. Remeber to un-check the "demo-mode" box !
