<div dir="ltr">Hi Joe,<br><div><br></div><div>Thanks for the reception report! You can look at the listener's report interactive map <a href="https://alexander.n.se/en/listeners-reports-interactive-map/">here</a>.</div><div><br></div><div>Jonathan</div><div>KC3EEY</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Feb 19, 2023 at 1:29 PM Jonathan <<a href="mailto:emuman100@gmail.com">emuman100@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi All,<br><div><br></div><div><div dir="ltr">I
wanted to share my 02/13/2023 SAQ transmission report. <br></div><div dir="ltr"><br></div><div dir="ltr">Using
vtsid, I set it up to record the amplitude of SAQ just to see if I
could see any possible signal from the 1500UT transmission. This looks
promising:</div><div dir="ltr"><div><span style="opacity:0.0001"></span></div></div><img src="cid:ii_lebpvmya1" alt="Screen Shot 2023-02-13 at 9.21.18 PM.png" width="562" height="179"><br><div><br></div><div>While
a lot of it looks pretty noisy, it looks like there was some signal
around the time of the transmission at 1500UT. Zooming in looks even
more promising:</div><div dir="ltr"><div><span style="opacity:0.0001"></span></div></div><img src="cid:ii_lebpw8t02" alt="Screen Shot 2023-02-13 at 9.21.48 PM.png" width="562" height="177"><br><div dir="ltr"><br></div><div dir="ltr">It
could just be noise peaks, but their duration seemed too long for
noise, so I was hopeful! To be sure, I wanted to look at the
non-coherent spectrum. Using vlfrx-tools, I used this signal pipeline
from the raw data I pulled from the signal store and ran it through
vtnspec, integrating over the transmission duration:</div><div dir="ltr"><br></div><div dir="ltr">vtcat -T2023-02-13_14:49,+12m 2023-02-13_14-00p1.5h_SAQ_test_and_main.vt | vtnspec -f17200 -w200 -r1 -av > SAQ220213.dat</div><div dir="ltr"><br></div><div dir="ltr">I
used vtcat to send only the transmission duration to the input of
vtnspec with a center frequency of 17200 Hz, 200 Hz wide, at a
resolution of 1 Hz. Using gnuplot, I plotted SAQ220213.dat using the following script:</div><div dir="ltr"><br></div><div dir="ltr"><div>echo "set terminal png small<br> set style data lines<br> set xlabel 'Frequency, Hz'<br> set ylabel 'Relative amplitude'<br> set nokey<br> set title '2021-12-24_07:46:00,+16m in 1Hz'<br> plot 'SAQ122421.dat' using 1:2<br> " | gnuplot > SAQ122421.png</div><div><br></div><div dir="ltr">This produced the following plot:</div><div dir="ltr"><div><span></span></div></div></div><img src="cid:ii_lebpush20" alt="SAQ230213.png" width="562" height="422"><br><div><br></div><div dir="ltr">Peaking
only a little bit above the noise a very promising peak of SAQ's
signal! Compared to Christmas Eve of 2021, this is much more centered at
17.2 kHz. Well done getting such an old transmitter as spot on as this
transmission is! Here is vtnspec's output:</div><div dir="ltr"><br></div><div dir="ltr">vtnspec: amplitudes 0 m/p/r: 4.557e-06 6.411e-06 1.407 p-m 5.01 sigma<br></div><div dir="ltr"><br></div><div dir="ltr">Now,
the real test is the listening test. Using the following pipeline, I
produced a wav file from the data, running it through some filtering:</div><div dir="ltr"><br></div><div dir="ltr">vtcat
-T2023-02-13_14:49,+12m 2023-02-13_14-00p1.5h_SAQ_test_and_main.vt |
vtfilter -h bp,f=17200,w=1000 -g100 | vtmult -f 16700 | vtmix -c 1,-j |
vtraw -ow > SAQ230213.wav</div><div dir="ltr"><br></div><div dir="ltr"><div>Again,
vtcat pulls the duration of the transmission and runs it through
vtfilter at the 17200 Hz center frequency, 1000 Hz wide, adding a gain
of 100. It's then sent to vtmult and vtmix to downmix down to 500 Hz,
then converted to wav. I used lame to convert it to mp3:</div><div><br></div><div dir="ltr">lame -b64 -m m SAQ230213.wav SAQ230213.mp3<br></div><div dir="ltr"><br></div><div dir="ltr">You can listen to it <a href="https://drive.google.com/file/d/13voNd4aXxw9kWNZ4vHlwOoXceTzeN9V5/view?usp=share_link" target="_blank">here</a>.</div><div><br></div></div><div dir="ltr">Since
the signal was pretty close to the noise floor, it blends in with the
noise pretty well, but if you listen very carefully, you can hear the
message!! Using smaller bandwidths didn't give me the desired tone due
to the fact the filter is a brick wall filter, so I decided to use the
Butterworth bandpass filter in sox, 20 Hz wide center at 500 Hz, also
adding a gain of 20 to make it even more audible:</div><div dir="ltr"><br></div><div dir="ltr">sox -v 20 SAQ230213.wav SAQ230213_20Hz_g20.wav bandpass 500 20</div><div dir="ltr"><br></div><div dir="ltr">Encoding to mp3 again using lame:</div><div dir="ltr"><br></div><div dir="ltr">lame -b64 -m m SAQ230213_20Hz_g20.wav SAQ230213_20Hz_g20.mp3</div><div dir="ltr"><br></div><div dir="ltr">You can listen to it <a href="https://drive.google.com/file/d/1dDOM6GrHj79ggzeyuyHkIAR7qlWh82i-/view?usp=share_link" target="_blank">here</a>.
It's much easier on the ears this time and makes copying the message
much easier. There was much less fading this time, but possibly due to
the fact that the transmission occurred during local daytime. It's
really cool that signal processing can bring this transmission out of
the noise! A huge thanks to Paul for helping me with this last year and
for his vlfrx-tools software.</div></div><div dir="ltr"><br></div><div>Can anyone copy the message from my audio file and decode it? If you can, please post it to this thread.</div><div><br></div><div>Thanks.</div><div><br></div><div>Jonathan</div><div>KC3EEY</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Feb 13, 2023 at 12:21 PM Joe Hobart <<a href="mailto:nova@npgcable.com" target="_blank">nova@npgcable.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Jonathan,<br>
<br>
Nothing heard here or seen on WF at or around 17.2 kHz from 1200 to 1530 UTC.<br>
Plenty of other signals present. Due to distance and time of day, the<br>
non-detection of SAQ was considered likely.<br>
<br>
Good copy from youtube.<br>
<br>
Here is a screen grab typical of the listening period showing at least 4 Navy<br>
transmitters and other signals. The carrier at 15 kHz is a locally generated<br>
weak signal. The intermittent carrier at 18 kHz is unknown.<br>
<br>
73,<br>
Joe, W7LUX<br>
Flagstaff, AZ<br>
<br>
<br>
On 2/13/2023 8:11 AM, Jonathan via TangerineSDR wrote:<br>
> Hi All,<br>
> <br>
> Reminder, the SAQ transmission is currently going on. (15:00UT)<br>
> <br>
> Jonathan<br>
> KC3EEY<br>
> <br>
<br>
<br>
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