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Lorenzo
Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy
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Posted: Mon Dec 06, 2010 2:53 pm Post subject:
Citizen Band Radio Frequency Interferences |
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Hi,
a lot of years ago I like to speak with my two-way radio.
Do you know the sounds of those transceiver ? uiii sfi wiwee
may radio work around 27Mhz... but frequences like LF, MF, HF or high frequnces like SHF maybe have more "coloured" sounds.
Do you know how can I reproduce these kind of sounds? _________________ Yes!
Oh Yeah!
Wow! |
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iopop3
Joined: May 28, 2010 Posts: 94 Location: Malmö, Sweden
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EdisonRex
Site Admin
Joined: Mar 07, 2007 Posts: 4579 Location: London, UK
Audio files: 172
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Posted: Tue Dec 07, 2010 1:51 am Post subject:
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In general, one of the characteristics of "low fidelity" communications such as AM radio, telephone, intercom, tannoy etc is "narrow bandwidth"; all of these technologies had anything but a flat response curve for the actual signal.
For AM radio technologies, without getting too technical, there were three components to the output. One was the actual demodulated signal, usually tuned into a fairly narrow band of 300-3000Hz in order to reproduce voice. Below 300Hz, the main component of sound is noise, and above 3000Hz, the main component are artifacts of the demodulation (sidebands) and of course noise.
So a bandpass filter 300-3k, some kind of amplitude modulation byproducts, and some good old fashioned noise, in judicious mixing. _________________ Garret: It's so retro.
EGM: What does retro mean to you?
Parker: Like, old and outdated.
Home,My Studio,and another view |
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beautyofdecay_
Joined: Aug 14, 2009 Posts: 38 Location: Netherlands
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Posted: Tue Dec 07, 2010 11:13 am Post subject:
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The best way to get that kind of noises is to use a shortwave radio.
VHF and higher (140MHz and up) usually doesn't have very good propagation of radio waves (reflections in the atmosphere so the radio signal is transported over a very wide range) and you just hear white noise.
Short wave however has very interesting noises, bleeps and digital communications.
Long time ago we recorded a track using an shortwave receiver tuned and detuned to a Morse code transmission, fed into a very long hall effect. It really added a surreal atmosphere to the track.
Great stuff for (random) experimentation
Just look for a second hand shortwave receiver (capable of receiving 1-30MHz), use a long wire as antenna and you're ready to go. |
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Lorenzo
Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy
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Posted: Thu Dec 09, 2010 12:05 pm Post subject:
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Thank you, EdisonRex!
beautyofdecay_ wrote: |
Long time ago we recorded a track using an shortwave receiver tuned and detuned to a Morse code transmission, fed into a very long hall effect. It really added a surreal atmosphere to the track. |
It is what i did with my AM/MW/SW valve radio... it is very funny "drumming" on the antenna... swish-swi-swi-swii swi-shhh
...
Yes I think it is easyer an Old-Man shortwave radio
do you think VHS "walkie-tolkie" is ok? mmmh
the 27Khz voice "distortion" is something unique!!! !!!!
http://www.youtube.com/watch?v=vrmdXunz_Co&feature=related
YES!!!! I love it!!!!
But... how can I make this kind of "modulation"??? _________________ Yes!
Oh Yeah!
Wow! |
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LektroiD
Joined: Aug 23, 2008 Posts: 1019 Location: Scottish Borders
Audio files: 2
G2 patch files: 2
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Posted: Sat Dec 11, 2010 7:35 am Post subject:
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I managed this effect using the level mod / level multiplier (I can't remember which). I used random waveforms on the LFOs modulating the oscillator to create the short wave sweeps, then combining that and my voice with the level multiplier on the G2.
I used it in a track called Solar Storm to sound like a news reporter was coming through on a weak radio signal. Unfortunately the snip on iTunes/Amazon doesn't feature that section. _________________ LektroiD |
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Lorenzo
Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy
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Posted: Mon Dec 13, 2010 5:17 am Post subject:
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LektroiD wrote: | level mod / level multiplier
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This sounds to me as something completely unknown _________________ Yes!
Oh Yeah!
Wow! |
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LektroiD
Joined: Aug 23, 2008 Posts: 1019 Location: Scottish Borders
Audio files: 2
G2 patch files: 2
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beautyofdecay_
Joined: Aug 14, 2009 Posts: 38 Location: Netherlands
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Posted: Mon Dec 13, 2010 11:44 am Post subject:
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What you hear in the youtube movie are USB (Upper Side Band) transmissions. These are so-called single side band (SSB) transmissions where only one side of the spectrum (upper or lower sideband) is transmitted and there is no carrier signal (like with FM transmissions where both sidebands are transmitted).
The "funny" modulation is created when you tune the radio above or below the (suppressed) carrier signal with as result that the audio content is shifted up or down in frequency.
I guess you can simulate that effect by using a pitch shifter.
As the audio bandwidth normally is 3 kHz the higher frequencies are also more attenuated than the lower ones as the audio band is shifted up or down, so that's also something to take into account.
So basically, the audio content is being shifted in frequency while at the same time a low pass filter is being applied. |
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Lorenzo
Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy
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Posted: Wed Dec 15, 2010 2:49 pm Post subject:
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beautyofdecay_ wrote: |
So basically, the audio content is being shifted in frequency while at the same time a low pass filter is being applied. |
oooh, yes... I have to try!
LektroiD wrote: | Here's a G2 patch, designed for the demo |
thank you very much! I'll download the demo as soon as possible!
I haven't G2... _________________ Yes!
Oh Yeah!
Wow! |
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Lorenzo
Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy
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Posted: Sun Jun 05, 2011 1:04 am Post subject:
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ouch! I forgot this post!!! _________________ Yes!
Oh Yeah!
Wow! |
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