#### solaris9123

Joined Dec 23, 2014
10
I get the basic idea.
static is a collection of random electrons that are picked up on accident in a radio, in the IF stage of the tuner.
it is essentially a mass attenuation of background radiation generated from power lines, cell phones, computers and other electronics that produce RF energy; whether by design or as a byproduct.
but is the static that we hear when our radios are out of tune, or the snow we see on a weak TV channel really caused from deep space radiation, left over by decaying stars and such?
or is it really just man made noise from our own electronics?
is static all around us? If you were to take a radio and encase it inside a lead vault; completely blocking any and all radio waves from reaching it, would it still produce sound?

#### BeerBelly

Joined Dec 16, 2013
30
Noise comes from many sources, depending on the frequency of interest. Much of the noise comes from the mixer and demodulator/detector stages in the receiver. Much of the noise also comes from the air molecules bumping against each other and the antenna or radio active decay of materials.

#### #12

Joined Nov 30, 2010
18,222

Hmmm. Wrong answer. I was thinking Thermal noise. Boltzman?
Yep. That's it.
Electrons moving in resistors cause noise.

#### takao21203

Joined Apr 28, 2012
3,702
The ionsphere is conductive

#### alfacliff

Joined Dec 13, 2013
2,458
some modes are inherently noisy, if you disconnect the antenna, an fm radio still has a lot of noise due to the type of detector used. on any other type of radio, with the antenna disconnected and a dummy load connected instead, the internal noise of the radio can be heard. connect the antenna, and you pick up radiated noise plus the internal noise.

#### BR-549

Joined Sep 22, 2013
4,938
One of the interesting properties of matter(particles) is that it hums or sings. All particles have voice and they never shut up. If you could hear just one particle, you would hear a constant steady tone.

The free electrons in current have a medium pitch song. The electrons in the nuclear shell of an atom of the conductor have a very low pitch voice. The protons of the conductor have a very high pitch.

Usually the song we want to listen to is the free electrons, so we call that song.....the signal.
And all that other singing going on is what we call noise or static and we don't want to hear that.

So static and noise is a universal chorus from matter, and the signal is the song we want out of it.

#### MikeML

Joined Oct 2, 2009
5,444
99% of the noise you hear on AM broadcast or ShortWave receivers is either atmospheric (lightning), or man-made (%$#%& Chinese Switching Power Supplies). Only if you disconnect the antenna, and then turn-up the RF gain to maximum (if so equipped) would you hear electronic noise produced inside the receiver itself. You would have to go to great lengths to erect special very-high gain antennas, in a low-noise rural area, to be able to receive cosmic noise. If you tune between stations (or disconnect the antenna) on an FM receiver, the noise you hear is produced in the receiver itself. An FM receiver has such high gain that it amplifies the electronic noise produced in its own front-end amplification and mixer stages. #### takao21203 Joined Apr 28, 2012 3,702 99% of the noise you hear on AM broadcast or ShortWave receivers is either atmospheric (lightning), or man-made (%$#%& Chinese Switching Power Supplies). Only if you disconnect the antenna, and then turn-up the RF gain to maximum (if so equipped) would you hear electronic noise produced inside the receiver itself. You would have to go to great lengths to erect special very-high gain antennas, in a low-noise rural area, to be able to receive cosmic noise.

If you tune between stations (or disconnect the antenna) on an FM receiver, the noise you hear is produced in the receiver itself. An FM receiver has such high gain that it amplifies the electronic noise produced in its own front-end amplification and mixer stages.
it was hissing and crackling the same way in the 1980s already.

#### MikeML

Joined Oct 2, 2009
5,444
it was hissing and crackling the same way in the 1980s already.
Not as bad as it is nowadays, what with LCD and LED wide-screen TV, CFLs, LED lighting, Solid-state ballasts for florescents, SMPS on computers, phones, modems, networks, furnaces, air-conditioners, battery chargers, etc...

How do I know? I have been an active Ham for going on fifty years...

#### takao21203

Joined Apr 28, 2012
3,702
Not as bad as it is nowadays, what with LCD and LED wide-screen TV, CFLs, LED lighting, Solid-state ballasts for florescents, SMPS on computers, phones, modems, networks, furnaces, air-conditioners, battery chargers, etc...

How do I know? I have been an active Ham for going on fifty years...
OK I think you are right for HAM/Shortwave.

Trains, electric cars too. you might be able to "hear" them if you are close to a railway or motorway

#### alfacliff

Joined Dec 13, 2013
2,458
not just for am/fm frequencies, there is a lot of radiated noise up into microwave frequencies too. and with companies putting internet on power lines, even more has appeared. many things that were not ment to be used or intended as radiators are now being used as such. also, the higher frequencies used in modern equipment makes more noise generated as well as needing more filtering to stop the radiation.

#### takao21203

Joined Apr 28, 2012
3,702
not just for am/fm frequencies, there is a lot of radiated noise up into microwave frequencies too. and with companies putting internet on power lines, even more has appeared. many things that were not ment to be used or intended as radiators are now being used as such. also, the higher frequencies used in modern equipment makes more noise generated as well as needing more filtering to stop the radiation.
Bad times for HAM radio enthusiasts, good time for magnetic parts manufacturers / sellers.
No wonder EMI ferrites are easy to buy from distributors and there are so many kinds.

#### alfacliff

Joined Dec 13, 2013
2,458
if manufacturers would only learn and spend the money to use them. there was even a sony tv that transmitted a fair amount of rf on 121.5 mhz, the downed pilot locator frequency. as I said, its not just hams.