W2VJN wrote:
> C added to C2148 Rise time Fall time Duty cycle Speed
>
> 0 1.5mS 1.2mS 50% 40WPM
> 0.05uF 2.5 2.2 48.3 40*****
> 0.1uF 3.0 2.5 46.7 40
>
> ****** Preferred mod. C added = 0.05uF and R shunt = 91K.
>
> The preferred mod listed above reduces the CW bandwidth by approximately
> the ratio of the fall time after mod to that before mod or 2.2/0.8 =
> 2.75x. Yet it preseves and even improves the CW duty cycle over the
> unmodified radio performance.
A word of a caution. 2 mS, while better than the stock waveform, is
still far too fast for proper keyclick suppression. It is much faster
than needed, and faster than the ARRL's recommended 5 mS.
We really should slow the rise and fall times down to 5 mS or
LONGER. With the resistor added to the mod, it might be
advisable to add enough capacitance to get the rise and fall as
close to 6 or 7 mS as possible.
When I have more time I'll build some sort of active filter that gives
a better waveshape than the single pole R/C filter. But for now
anything that slows the 1000MP's waveform down is a good idea!
73, Tom W8JI
W8JI@contesting.com
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