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wip: docs

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Andreas Eversberg 2016-05-10 19:23:11 +02:00
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docs/c-netz.html
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@ -148,12 +148,14 @@ Let it run again for one hour and you will see that signal is now below 1 PPM.
<center><img src="c-netz-burst_part.png"/></center>
<p>
C-Netz uses FSK by directly modulating the carrier, rather than modulating an FM tone.
C-Netz uses FSK (Frequency Shift Keying) by directly modulating the carrier, rather than modulating a transmitted tone.
The advantage is much higher data rate.
A phone will only detect the correct polarity.
The base station's carrier frequency is raised by 2.5 KHz to transmit a logical "1" and lowered by 2.5 KHz to transmit a logial "0".
(The mobile station transmits reversed polarity.)
The mobile station will only detect the correct polarity.
The three sync words of "11100010010", is shown in the picture above.
In the picture above, the polarity is wrong.
The "1" points down and the "0" up.
(The logical "1" points down and the logical "0" points up.)
You must check, with what polarity your transmitter is doing a positive frequency deviation.
Also you must check your sound card's polarity on positive value beeing sent.
To change polarty, use command line option '-F' or '--flip-polarity'.
@ -161,8 +163,8 @@ To change polarty, use command line option '-F' or '--flip-polarity'.
</p>
<p>
This software does not care about what polarity it receives.
It just checks for sync words at both polarities and chooses right polarity automatically.
This software does not care about what polarity it receives from the mobile station.
It just checks for sync words with both polarities and chooses right polarity automatically.
</p>
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