[1000mp] Key Clicks -- My MP Experience

[Ian White, G3SEK]

George,  W5YR wrote:
>Harry, unfortunately it is not as simple as that. One of the key 
>factors in determining click bandwidth is the manner in which the 
>keying waveform is accomplished. Specifically, all transitions from off 
>to leading edge onset to leading ledge completion to full power on, and 
>the trailing edge counterpart, all tend to contribute added bandwidth 
>unless the transitions are "smooth." Sharp on/off transitions generate 
>probably as much excessive bandwidth as does an overly short rise/fall time.
>

ARRL's "target" figure of 5ms should give plenty of time for a clickless 
transition... but only if the *shape* of the transition is right too.

What we need to identify are *exactly* which features of the waveshape 
are causing the wideband clicks. Is it the average rise time, or the 
sharpness of the corners... or both? Which features are important, and 
which don't matter much? Unfortunately that kind of insight needs some 
high-powered mathematical input.

By coincidence, a ham in Europe who is a DSP expert and a high-powered 
mathematician has recently started to get interested in this problem. 
When there's news, I'll report back.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek