On Mon,4/10/2017 7:45 AM, Jim Thomson wrote:
Get your buddy K6XX to fix the lousy TX imd on the K3. Its on
a sweep tube level. -23dbc for IMD-3. The 10 watt version of that K3
is no better either. It needs a serious re-design of the entire pa section.
IMD in the K3 and K3S are a function of output power and DC supply
voltage. ARRL tests at rated power, where IMD is highest. IMD is
considerably lower at 50W, which is what is needed to drive most amps to
legal limit. And 4X6GP has noted more recent ARRL lab test data. K6XX
showed data in this talk to NCCC in 2013.
http://k9yc.com/K6XXAmpTalk.pdf
More to the point -- when I have done careful measurements of occupied
bandwidth of a small sample of rigs and amplifiers, and also compared
ARRL data for CW bandwidth, the K3, K3S, and now the Flex radios with
their latest firmware are the cleanest rigs on CW, by far. Next below
them is the TS590. And on SSB, using pink noise (an excellent audio test
signal that simulates speech content) or actual speech, there is
virtually no difference between a K3 driving a Titan 425 or KPA500 and a
FT1000 Mark V Field at full power or at half power. And the bandwidth of
the K3 driving the Titan or the KPA500 is virtually the same as with the
K3 barefoot at the level it's driving the amp.
My measurements are here. :http://k9yc.com/P3_Spectrum_Measurements.pdf
Comparisons of ARRL data is here. http://k9yc.com/TXNoise.pdf This
summary was done in 2014.
73, Jim K9YC
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