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Old 05-14-2018, 8:48 PM
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Default nxdn

Is nxdn a true square wave signal? Being digital, i am assuming so.
Some nxdn waves appeared somewhat rounded off that were depicted on an info page.

Is there a preamp that can be used with nxdn that wouldnt interrupt the nxdn waveform?
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Old 05-15-2018, 1:05 AM
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There is no such thing as a "true" square wave signal, especially in radio communications. A perfect square wave actually requires an infinite number of odd harmonics of the fundamental frequency, which is why switching power supplies are notorious for generating RFI unless properly shielded and filtered, and overmodulated CBs splatter RF hash across several adjacent channels. Any signal that lives within the confines of a typical communications channel's bandwidth will not be a perfect square wave because the frequency components needed to make it "perfect" fall outside the bounds of the channel.
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Old 05-15-2018, 8:31 AM
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NXDN is simply another form of Continuous 4-level Frequency Modulation (C4FM) which is also known as 4FSK on an FM carrier. It's the same type of modulation P25 and Yaesu's System Fusion use. Essentially, its a FM signal where the carrier is shifted between 4 points (between -1.8 kHz and +1.8 kHz of center frequency) to designate different symbols of the digital stream.
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Old 05-15-2018, 11:12 AM
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Quote:
Originally Posted by vocoder View Post
Is nxdn a true square wave signal? Being digital, i am assuming so.
Some nxdn waves appeared somewhat rounded off that were depicted on an info page.
No RF signal is a true square wave. All "digital" signals are *analog* transmissions that encode digital information.


Quote:
Is there a preamp that can be used with nxdn that wouldnt interrupt the nxdn waveform?
There is nothing special about NXDN signals. A preamp that works with analog voice signals will work exactly the same with NXDN, DMR, P25, TETRA, ProVoice, D-Star, Fusion or any other digital voice protocol.
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Old 05-15-2018, 9:15 PM
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Quote:
Originally Posted by slicerwizard View Post
No RF signal is a true square wave. All "digital" signals are *analog* transmissions that encode digital information.


There is nothing special about NXDN signals. A preamp that works with analog voice signals will work exactly the same with NXDN, DMR, P25, TETRA, ProVoice, D-Star, Fusion or any other digital voice protocol.
Finally, someone on RR that understands RF.
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