> When I first received my Icom 756Pro (now my backup rig) several years > ago I discovered that the default rise/fall times (adjustable in one of > the menus) was set to 2 msec (!). That's unconscionable...
It's unconscionable with some rigs, but not all. Take a look at the K3's keying envelope on a scope since the ca. 3.00 firmware release earlier this year. Compare it against the QST Product Reviews. I currently measure the rise time of about 2.5 msec and the K3 occupies minimal RF spectrum. Even at very fast CW speeds, it's the slope of the rise and fall that primarily determines occupied bandwidth. As keying speed increases, there's a point where the keying rate becomes a dominant factor but that's largely due to the fact that as the keying rate increases so must the envelope slope. The clicks heard with many transmitters occurs because the slope is discontinuous. Using a Blackman-Harris or raised-cosine window function minimizes occupied bandwidth but that function is also dependent on envelope distortion created by a transmitter's ALC circuitry. So, it's possible to set two completely different brands of transmitters to 2 msec and the bandwidth results can be radically different. Paul W9AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
