On 26/12/2010 09:55, Szczepan Bialek wrote:

Uzytkownik "joe" napisal w wiadomosci
...
Szczepan Bialek wrote:

"K1TTT" wrote
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On Dec 25, 2:57 pm, joe wrote:
K1TTT wrote:

distance itself does not affect sidebands.

frequency dependent dispersion in the ionosphere can affect
sidebands
and the mark/space tones of rtty differently over short periods
causing differential fading and distortion.

One could also consider selective fading.

that's just another name for it... i threw in the big words because
i'm sure that mr.b will look them up out of context and find all sorts
of hilarious ways to recombine them.

http://dj4br.home.t-link.de/ssb3e.htm
I am sure that the all my questions will be explained with the
ionosphere. The first my question was on the frequency doubling.
But yours selective fading means for me "distance itself does affect
sidebands". So you are very helpfull.


But you fail to recognize that distance ALONE does NOT affect
sidebands differently. It requires something else to be present.


Whilst distance does not affect sidebands per se, it can affect which
sidebands are received, and hence the envelope of a recovered signal.

Consider a pulse train with a spectrum that extends to infinity; the
higher order sidebands when received by a distant station will be below
the noise floor and will not play a part in the recovered pulse train,
so in a way distance has modified the spectrum of the received signal!!

Jeff