Jim,
Interesting results, especially the dramatic difference in the FTDX5000 after the firmware update. The K3 looks great. Hopefully the K4 will be at least as good. Ed / w2rf -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Jim Brown Sent: Tuesday, June 9, 2020 3:46 PM To: [email protected] Subject: Re: [Elecraft] CW rise time setting 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> 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 ______________________________________________________________ Elecraft mailing list Home: <http://mailman.qth.net/mailman/listinfo/elecraft> http://mailman.qth.net/mailman/listinfo/elecraft Help: <http://mailman.qth.net/mmfaq.htm> http://mailman.qth.net/mmfaq.htm Post: <mailto:[email protected]> mailto:[email protected] This list hosted by: <http://www.qsl.net> http://www.qsl.net Please help support this email list: <http://www.qsl.net/donate.html> http://www.qsl.net/donate.html Message delivered to <mailto:[email protected]> [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
