Several observations. First, MANY years ago thoughtful engineers
listened with headphones to the distortion output of instrumentation
devices (like legacy distortion analyzers) as "ear training" to help us
recognize a particular form of distortion. An very smart former Ampex
engineer designed and sold an extremely useful instrument to measure wow
and flutter in analog tape machines. I used the distortion output of
that device to train my ears to hear the scrape flutter as the tape
passed over the playback and recording heads, as I had many years
earlier to hear harmonic distortion.
Any non-linear distortion mechanism produces both intermod and harmonic
distortion. Two big parts of the difference are 1) how we measure it;
and 2) which physical devices produce more or less of each so that one
or the other is dominant. Both produce, in our application, signals that
shouldn't be there. 40 dB down is pretty good for most consumer systems,
but could produce spurs from it to someone who hears us very loud . If,
for example, someone is 40 dB over S9, harmonics that are 40 dB over S9
would be S9! Sort of negates the advantage of some WSJT-X modes if the
signal you're trying to copy is only S8.
73, Jim K9YC
On 2/15/2021 12:53 AM, Reino Talarmo wrote:
Hi Mike and Bill,
I looked those *.wav files using v2.4.0-rc1 and noted interesting
presentation difference, when I had Flatten activated or non-activated.
Especially the waterfall display changed a lot. It was difficult to see
those multiple sidebands in non-flatten display totally independent of
gain and zero settings. In spectrum display I can see the carrier and
weak sidebands at 310 Hz or so. In both flattened and non-flattened
spectrum other than the 310 Hz sidebands are really weak some are just a
pixel or two and others none.
Could the flattening do more than modify the frequency amplitude and be
an additional reason for a bad waterfall display?
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