"Wimpie" napisal w wiadomosci
...
On 24 mar, 10:53, "Szczepan Bialek" wrote:
"This finding had practical applications for telegraph communications.
For
example, Heaviside actually solved one of the biggest problems affecting
long distance telegraph and telephone communication in 1887 -distortion.
It
was known that different frequencies travel with different speeds on a
long
cable. For example, the low bass frequencies in a voice signal travel
faster
than the high treble frequencies. When the cable is long enough, the
frequencies smear, and both voice and telegraph signals become garbled
noise. Heaviside used his equations to show that if inductances (i.e., a
small coil of wire) were added along the length of the cable, the
distortion
could be reduced."
From:http://www.ieeeghn.org/wiki/index.php/Oliver_Heaviside

" It was known that different frequencies travel with different speeds on
a
long cable".

Is the same in air and space?
S*

Hello Szczepan,

Search for the effective permittivity of media with free electrons
(plasma). You will see that the effective permittivity changes with
frequency, hence the phase velocity. Don't look strange to find
apparent permittivities below the value for vacuum.

Just ignore DC magnetic field as this complicates that math
significantly.

Hello Wim,

So you confirm that in plasma is the same as in metal.

But what with the space. The AM should be better than FM to communicate with
the Mars.
Is/were FM used for long distances?

Were done the proper experiments in the early years of radio?
S*