The static on analog televisions has been attributed to Cosmic Microwave Background (CMB) radiation by a variety of scientific sources such as CERN, NASA and this primer from Douglas Scott ( University of British Columbia)
Can I see the CMB for myself?
In fact you can! If you tune your TV set
between channels, a few percent of the "snow" that you see on your
screen is noise caused by the background of microwaves.
CMB radiation is in fact considered the best available evidence of the Big Bang Theory. So far from being a myth, this is used to prove the Big Bang happened.
The actual amount of static attributed to BB is debatable. CERN and NASA do not state a number.
The 1% as the amount of static caused by BB is claimed on various other sources with no clear explanation of how it is measured at 1% and whether the other 99% covers all sorts of things, including stuff induced from sparks, lightning, stars.
The claim is found in this presentation by Prof Frank Van Den Bosch from Yale (slide 4) and another on the University of Buffalo, NY, Physics Dept (PPT)
Roughly 1 percent of the static on your TV is CMB!!!
Lots more links to Theory
Now, why did I mention analog earlier? Because with digital signals, you will no longer see leftover radiation from the Big Bang as static on your television screen.
when you are between channels on an analog television, the snow that
you see on the screen is made up of interference from background
signals that the antenna on your TV is picking up. Some of the “snow”
is from other transmissions here on Earth, and some is from other
radio emissions from space. Part of that interference – about 1% or
less – comes from background radiation leftover from the Big Bang,
called the Cosmic Microwave Background (CMB). The same is true for FM
radios – when the radio is tuned to a frequency that is between
stations, part of the hiss that you hear, called “white noise”, is
leftover radiation from the Big Bang some 13.7 billion years ago
Digital signals eliminate the interference while watching a program
because instead of broadcasting the picture as a radio wave which
communicates to the CRT or plasma screen what to “paint” on the screen
by the frequency of the signal, all a digital signal communicates is a
1 or 0, and the digital converter takes care of decoding and sending
information as to what the picture and sound on your screen should