Topband: MP clicks

[Tom Rauch]

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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