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<title>Psk Modes</title></head>
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<td style="text-align: center;"><img alt="" src="BPSK31-18db.png">
<br>BPSK-31, imd = -18 db, about 6 dB of ALC
<br><a href="BPSK31-18db.wav">Sound</a>
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<td style="text-align: center;"><img alt="" src="BPSK31-14db.png">
<br>BPSK-31, imd = -14 db, about 12 dB of ALC
<br><a href="BPSK31-14db.wav">Sound</a>
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<br><br>These are examples of what <b>not</b> to do on the ham bands.
<br><br>In both cases the audio drive to the transmitter was set too
high, either by mistake or because the operator thought that more power
is better. When the audio stages of the transmitter are over driven
with clipping then you might possibly see 3rd harmonic audio images of
the psk signal. They will be 3x as wide.
<br><br>Be careful when evaluating a received signal. The receiver
might also be overdriven and result in similarly distorted waterfall
signatures. You can always check your local signal path by inserting 20
dB of attenuation at the antenna. If things get better then the
distortion is in the receiver and not in the transmitter.
<br><br>You <b>cannot</b> achieve better communications by overdriving
the audio on any of the digital modes that require linearity.
These include all of the modes that have an amplitude modulation
component. Some like Psk and Throb have both an amplitude and
frequency or phase modulation component. An overdriven signal may
produce more decoder errors than a properly driven signal of lesser
power. This is particularly true for all variants of PSK.
<br><br>The only fldigi modes that are not subject to this are: MFSK, DOMINOEX and THOR.<br><br>All signals shown in x2 waterfall mode, tick marks at 100 Hz intervals, waterfall palette is "blue-2"
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