WxSat provides a wealth of information on its operation in the Title
Bar. The title bar has 5 parameters showing current operational status.
While waiting for a satellite to arrive, (after selecting
Recording/Start at Subcarrier/Save bitmap and Wav), you will see
something like this:
Stand-by indicates the program is standing-by for a satellite signal to be received.
The Toggle=0 or 1 indicates the program is active and waiting to detect
the 2400 Hz subcarrier. The toggle denominates the two input buffers used for the DMA-transfer
of the sound data.
s is the signal strength of the subcarrier or the start/stop tones,
respectively. The corresponding threshold values can be adjusted in
Expert - Automatic Recording. Two s-parameters will appear for start
at tones.
s0.22 shows the current detected value of the subcarrier. With no audio
from receiver going to the program, the value is s0.00. With squelch
open, and receiving only background noise, I get between 0.18 and 0.22
readings in this field. I always run my squelch wide open while awaiting
a satellite, with loudspeaker turned off.
This signal indication is used to tell the program at which signal
strength it should decide that a satellite is being received, and start
the next detection phase. You can set the value you want (for each
individual satellite) in the Parameters/Decoding/Expert/Automatic
Recording - Automatic recording on Subcarrier options - Amplitude. For
example, while receiving a strong signal from NOAA 14, the value I see
in the title bar is around s2.40. So as the satellite comes into range,
I watch this value increase, and at s1.00 the signal is distinct but
still noisy, so I set the option to start on 1.00 for this satellite.
Lower values would make it more sensitive to false starts, or
horizon-hugging passes, and higher values will increase the delay in the
start of reception. In my case, a value of 0.50 to 1.50 would work just
fine.
Some satellites, like Resurs 01-4, have much lower maximum values in
this field - I get around 1.2 for a maximum, so I will set the AMPLITUDE to
0.50 for this satellite.
If Squ is 1, the signal is too noisy to detect a start tone. This is used if
Start at Start Tone option is selected - for Goes or Meteosats.
The last parameter, nc0+0, provides a digital timing delay, used by
Wxsat to prevent false starts. The default value is to count up to 12
timing units of 0.74 Seconds, to verify that the satellite signal is
still there, (with s parameter above the selected threshold), and then
start the final recording phase. Again, you can set the value of delay
for each satellite individually on the Subcarrier options window. I set
my value to 6 for start, and 12 for stop. The STOP value is critical for
allowing the program to continue recording or decoding during signal
fades or interference noise. With a value of 12 for the STOP parameter,
I would need at least 8.88 seconds of strong interference or fade before
WxSat would stop the current recording session. It would start a new
one, if the signal returned. If you experience frequent long fades, and
end up getting multiple files generated for each pass, then you might
want to increase this value to 20 or 30. One result will be that you
will also record more noise at the end of each pass before WxSat stops
processing based on loss of signal.
The final pre-recording step is to get 4 more counts of solid signal
before reception actually starts. This activity you can see in the
Title bar briefly as Toggle Sync=1 after nc=12 shows in the title
bar. Then the Toggle Sync changes to Processing XXXXXXXX status, and
the picture will appear on the screen, and/or get recorded in the file
name shown after the Processing.
Other things you may see on the title bar are:
w is the difference between the actually measured line length and the
nominal line length measured in subcarrier periods.
r is an internal threshold level for the quality of the h-sync
signal.
The accompanying diagram illustrates the way the different parameter settings
affect the program.
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