[AMPS] grid termination value and triple bypass.

[Rich Measures]

>
>Thank you for all the replies to my question about the grid term resistor
>selection. 
>
>Although I haven't had time to go back to Rich's site yet, I'd like to
>ask the 2nd half of the question.
>........
>With my TS-940's larger output, I'm trying to choose the optimum value
>for 4CX1000 design (or similar). Would this exciter allow me convenience
>in selection of the termination resistance.

€  The practical choices are 12.5-ohms, 50-ohms, 200-ohms and 450-ohms.  
Less ohms means better stability and swr.  The trade-off is more watts of 
drive are needed.  
>
>Also, would someone detail the term "triple bypass" the cold side of a
>resistor. Three separate types of capacitors, three different capacitors
>or three capacitors- same value in parallel?
... t
€  ... three capacitors of different values, in parallel. .  .   Above 
it's self resonant frequency, every capacitor looks inductive.  Thus, to 
optimally bypass a wide range of frequencies, several capacitors of 
different values are better than a single value.   For example, 0.02uF is 
a fair bypass below 5MHz, 0.002uF is a fair bypass up to 30MHz or so.  
100pF is a pretty good bypass at 100MHz. . Other values can be used.  
Lead lengths are important.    (note --  A vhf bypass on the cold-end of 
the grid terminating resistor is important because it improves vhf 
stability.)  
-  later 



Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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