[Elecraft] CW rise time setting

[Jim Brown]

On 6/9/2020 11:07 AM, Al Lorona wrote:
> The reduction in the sideband levels (what some folks here called 'clicks'... not sure that's a good name for this) varies depending on where you measure it, but in general the sidebands will drop anywhere from 0 to 12 dB-- sometimes less, sometimes more--  when you go from 2 msec to 8 msec rise/fall times. For instance, arbitrarily choosing an offset of 500 Hz from the carrier, the sideband drops by 11 dB for the longer rise time. That turns out to be a fairly typical value. And by the way, in general the sigmoid does a better job than a raised cosine.



I've not looked at the math, but I've measured more than a half dozen 
radios, most with variable time constant shaping, and Elecraft with 
their fixed sigmoidal shaping. The data is here.

http://k9yc.com/P3_Spectrum_Measurements.pdf

A K3 at 25W (driving a KPA500 to full power) is 50 dB down 230 Hz either 
side of the signal, 60 dB down at 305 Hz. At 40W driving a legal limit 
tube amp (Ten Tec Titan) sidebands at the power amp output are 50 dB 
down at 235 Hz, 60 dB down at 335 Hz.

A neighbor's FT1000 Mark V Field was 50 dB down at 665 Hz.

Another neighbor's FTDX5000 set for 6 msec was 50 dB down at 410 Hz, 60 
dB down at 1.05 kHz before the firmware update. It improved to -50 dB at 
310 Hz and -60 at 535 Hz after the update.

73, Jim K9YC