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Author Topic: Shortwave sounds I've always heard.  (Read 2116 times)
KC6RWI
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Posts: 170




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« Reply #15 on: April 05, 2019, 03:53:10 PM »

thanks for that, your post above indicates the amount of technical people tuned into this site.
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SM0AOM
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Posts: 254




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« Reply #16 on: April 06, 2019, 01:52:53 AM »

Returning to the original question, since you have heard this for a very long time, it probably is a more or less legitimate communications mode of some form.

If it would have surfaced during the last 10 - 15 years or so, spurious emissions from switching power supplies, TV/computer screens or data communications gear would have been the "prime suspects".

Some of these can generate very strange sounding effects.
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KC6RWI
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Posts: 170




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« Reply #17 on: April 06, 2019, 11:10:52 AM »

I am going to check the net once in awhile and see if i can find any mention of the sounds. I'll just keep my ears and eyes open. maybe I'll search 10 and 11 ssb meter sounds.
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WB0DZX
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Posts: 21




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« Reply #18 on: April 09, 2019, 11:34:02 AM »

Without hearing the signal, I'm only guessing. It may be one or more ground-based swept-frequency ionospheric sounders, i.e. ionosondes. Those are best heard with BFO modes (not AM or FM). It sounds like a swisher, best descibed as someone key down while quickly turning the VFO from a low frequency to a higher one sweeping through the frequency you are tuned to. That is what is automatically happening, synchronized to associated receivers doing the analysis.
 
They are used mainly for real time propagation analysis.
 
I couldn't find an easier link than this one. "Fast forward" to 28:15 (min:sec) i.e. -18:30 remaining.
https://www.magic.co.nz/home/archivedtalk/audio/2017/12/strange-shortwave-noises.html
 
A closed circuit version on assigned fixed frequencies throughout the HF spectrum is ALE: Automatic Link Establishment. However, it keeps track of the best path between each station in a network - not what ionospheric conditions exist. That is discussed earlier in the above audio.
 
Mike WB0DZX
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WB0DZX
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Posts: 21




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« Reply #19 on: April 09, 2019, 11:41:42 AM »

Also check out CODAR. Also earlier in the link. However CODAR is regular and periodic on certain fixed frequencies. It is a watery sound. BTW since the sound you describe is somewhat wideband, it would Not be a chirp (pulse) sounder.
 
Mike WB0DZX
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K5TED
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Posts: 229




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« Reply #20 on: April 09, 2019, 10:19:56 PM »

Whistlers are remarkable bursts generated by
lightning discharge. When part of the discharge
energy escapes the ionospheric barrier and propagates through the magnetosphere, whistlers can
be heard in radio receivers as a relative long
whistle decreasing in frequency, from about 6
kHz to a few hundred Hz (fig. 6). In the magnetosphere whistlers interact with free electrons
and are forced to propagate along the Earth’s
magnetic field lines. The harmonic components
of the signals identified as whistlers correspond
to electromagnetic waves that have traveled several Earth radii arriving at different times to the
observer. Lower frequencies are delayed 3-6 s
with respect to the higher ones. The dispersion of
a whistler depends on the length of the path over
which the signal travels as well as the characteristics of the propagation medium such as its electron density

https://www.earth-prints.org/bitstream/2122/3674/1/11bianchi.pdf
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WB0DZX
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« Reply #21 on: April 09, 2019, 10:23:09 PM »

Hi, K5TED. You may be referring to the swept frequency "signal" from lightning known as whistlers. I studied those for Project INSPIRE, a NASA-citizen scientist collaboration.
 
If so, their domain drops off sharply to nothing above 20 KHz (radio). Above that, including the area around 28 KHz, the sferics are run of the mill crashes that sound the same no matter what the frequency. They don't move and sound the same no matter the receive mode.
 
Mike WB0DZX
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WB0DZX
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Posts: 21




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« Reply #22 on: April 09, 2019, 10:31:43 PM »

Nobody is sure of the mechanism or how often it may occur, but my reception included what the national leader said was the only "reverse whistler." It went from high to low frequency in its sweep. No other such whistlers from that time slot.
 
I'm left-handed so that doesn't totally surprise me.
 
Mike WB0DZX
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WB0DZX
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Posts: 21




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« Reply #23 on: April 09, 2019, 10:34:39 PM »

Oops: next to last message show read 28 *** MHz ***!
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KC6RWI
Member

Posts: 170




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« Reply #24 on: April 10, 2019, 01:50:19 PM »

Thanks for all the interest, I spent sometime this morning checking some utubes. The closest thing I heard is over the horizon radar. There is just one problem with that. I just get one cycle and its random but who knows. I seem to get just parked on 10 or 11 meters, just one funny burst. Maybe its a test signal to check the equipment, Thanks again, Leonard
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