On 2/7/2020 4:00 PM, hb9...@hispeed.ch wrote:
I think these IMD3 values are not very impressive. A power amp. would
typically further degrade the overall results.
In practice, no, because the K3 and K3S IMD is significantly lower at
the power levels needed to drive an amp. My 87As need 45-55W, my KPA1500
30-50W, and KPA500 25-30W, in all cased depending on the band. IMD is
also minimized by running the radio near the top of its design range
13.8V nominal, 15V max).
So K3S is rather good for CW but not really good as SSB preference? (I have
now also a FTDX101MP)
When they were introduced, the K3 and K3S both pushed the state of the
art for CW bandwidth with low phase noise and a carefully shaped keying
waveform (that others took years to copy). My measurements of the TX
bandwidth of my K3 and several other rigs I was able to borrow are here.
http://k9yc.com/P3_Spectrum_Measurements.pdf
It's also important to realize that IMD increases CW bandwidth too,
because CW is actually 100% square wave amplitude modulation of the
carrier. Compare slide #9 with #14 - 16, for example. Those little humps
that look like sidebands are IMD, and are heard as clicks. Compare slide
#17 (100W SSB) with those that follow. Pink noise is used as a test
signal because it's spectrum and dynamics far more closely resemble
speech that white noise.
73, Jim K9YC
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