Paul Christensen wrote: >> 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 > Are you sure about 2.5 ms? As far as I remember I measured my K3 to about 5 ms and Elecraft also stated 5 ms. This was over a year ago however, if 2.5 is correct they have changed it or my memmory is corrupted.
/ SM2EKM ______________________________________________________________ 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
