But why do they use Mark and space measurements?Mark & space measurements are used in transmission circuits to check for modulation distortion of digital signals.
It's just an old name for modern digital parameters that dates back to sending Morse code. In RTTY the digital signal is transmitted by shifting the carrier by a fixed amount up or down from the carrier (FSK). These shifts are called Mark & Spaces that in a perfect world would have a 0% bias distortion if a perfect square wave (50% duty cycle) was sent. When information is sent in the form of digital codes mark & space measurements check to be sure that proper timing is present on the signal. So if we sent that signal in a circuit that had some type of distortion the duty cycle could change from 50% to some value that favored marks or spaces creating what's call a bias that would cause printing errors on the old mechanical teletype machines when sending real codes. For the long-range HF links I setup and worked in the Navy as a Technical Controller almost 40 years ago this was usually caused by skip or ionospheric conditions what affected the delay or signal strength of received signals at slightly different frequencies.But why do they use Mark and space measurements?
How does mark and space measurement tell the modulation distortion? i'm guessing pulse width, time period, duty cycle doesn't check for the modulation distortion of why is that?
Doesn't the time period, pulse width, duty cycle already give the same results or is it different and how so?
I'm new to this mark & space measurements, i'm not sure what it really is and how it's different and when it's used and why it's used
Yes true, but it seems that mark space ratio measurements are used to modulation waveforms, AM and FM modulation , phase modulation, modulation distortion , pulse width modulationFor example 50% duty cycle is identical to a mark space ratio of 1:1
by Jake Hertz
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