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I'm studying FM radio transmissions at the moment. I'm using an NTX2B transmitter to experiment naturally assumed I'd use 0V for False/No signal and 3V for True.

However, a lot of articles that I came across suggested using a DC bias, so that for a 3V supply, you get 0V for False, 3V for True, and ~1.5V for no signal.

Is there a particular advantage to using a DC bias like this?

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    $\begingroup$ There's no such thing as a DC bias on a FM signal, so this must be a thing about that transmitter in particular. Also, what you describe is not so much "bias" as adding a third state. Could you edit your question to add a schematic for or link to documentation of this transmitter you are using, and an example of the 'articles you came across'? That context would help. $\endgroup$ – Kevin Reid AG6YO♦ Jun 18 '17 at 0:00
  • $\begingroup$ This sounds more like a subcarrier like SCA or how the L-R signal is transmitted so it can be demultiplexed with the primary L+R main carrier for stereo. $\endgroup$ – SDsolar Jul 27 '17 at 2:01
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I have never heard about it, but my hypothesis is that it could be useful if there are multiple users trying to access the media and they listen before transmitting to avoid collision (something like CSMA/CD). If you don't have the "no signal" state, you can not differentiate between transmitting one of the symbols and not transmitting.

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Be aware that this is an amateur (ham) radio site and your question does not pertain to ham radio. But perhaps your project is a stepping stone to an interest in communicating further including around the world, with satellites, and the International Space Station.

The NTX2B transmitter module is for the transmission of data on 433 MHz. The data input to the module should be 0 volts or 3 volts to represent 0 and 1 respectively. No other voltage or bias should be used as it may result in erratic operation.

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