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 Forum index » DIY Hardware and Software
Citizen Band Radio Frequency Interferences
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Lorenzo



Joined: Nov 09, 2008
Posts: 349
Location: Trieste - Italyjstan

PostPosted: Mon Dec 06, 2010 2:53 pm    Post subject: Citizen Band Radio Frequency Interferences Reply with quote  Mark this post and the followings unread

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?

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iopop3



Joined: May 28, 2010
Posts: 95
Location: Malmö, Sweden

PostPosted: Tue Dec 07, 2010 12:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Prolly not exactly what you're looking for, but have you seen, http://ericarcher.net/devices/tit/ ?
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EdisonRex
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Joined: Mar 07, 2007
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Location: London, UK
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PostPosted: Tue Dec 07, 2010 1:51 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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beautyofdecay_



Joined: Aug 14, 2009
Posts: 38
Location: Netherlands

PostPosted: Tue Dec 07, 2010 11:13 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Wink

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: 349
Location: Trieste - Italyjstan

PostPosted: Thu Dec 09, 2010 12:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

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 Wink
...
Yes I think it is easyer an Old-Man shortwave radio
do you think VHS "walkie-tolkie" is ok? mmmh Rolling Eyes

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"???

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LektroiD



Joined: Aug 23, 2008
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PostPosted: Sat Dec 11, 2010 7:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Lorenzo wrote:
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"???


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.

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Lorenzo



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PostPosted: Mon Dec 13, 2010 5:17 am    Post subject: Reply with quote  Mark this post and the followings unread

LektroiD wrote:
level mod / level multiplier


This sounds to me as something completely unknown Embarassed

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LektroiD



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PostPosted: Mon Dec 13, 2010 7:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's a G2 patch, designed for the demo (which you can download here), if you have a hardware G2, let me know and I'll post a full version with mic input


RadioInterference.pch2
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 Filename:  RadioInterference.pch2
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beautyofdecay_



Joined: Aug 14, 2009
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Location: Netherlands

PostPosted: Mon Dec 13, 2010 11:44 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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Location: Trieste - Italyjstan

PostPosted: Wed Dec 15, 2010 2:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

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... Crying or Very sad Rolling Eyes Wink

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Lorenzo



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PostPosted: Sun Jun 05, 2011 1:04 am    Post subject: Reply with quote  Mark this post and the followings unread

iopop3 wrote:
Prolly not exactly what you're looking for, but have you seen, http://ericarcher.net/devices/tit/ ?


ouch! I forgot this post!!! Idea

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