> Given a significant number of parameters and the need to assess circuit
> performance over multiple values for each parameter, the resulting number
> of cases can be large. Varying each of 50 parameters through a 20% range
> in 1% increments yields 1000 cases. And while some parameters can easily
> be varied while measuring, others cannot; how does one step a tube through
> its tolerance range for contaminants, or through its tolerance ranges for
> inter-element spacings?
You are making mountains out of what turn out to be mole-hills. It's
pretty easy to find the extremes in phase shift and loss at several
points, and determine if oscillation is possible.
I think maybe the mental picture you have of the system is
incorrect, perhaps you are assuming wild gyrations on multiple
frequencies. Multiple complex resonances and feedback paths are
typical for "unclean" layouts, like a breadboard wooden chassis
PA with point to point wiring, but not in modern PA's with decent
construction.
By the time you measure all the parameters of concern, you likely
have most or all of the required answers.
> > Let me give you an example of how people assume models are
> > correct.
>
> Most engineering techniques produce erroneous results when badly
> practiced. The fact that some practitioners model poorly does not
> invalidate the virtues of competent modeling.
My point is the model would take longer to construct than the
measurements would take, and almost certainly not be able to
include anywhere near everything.
> > IMO, if modeling programs can't handle a simple inductor
> > properly...they need to be carefully watched with other components.
>
> Are you asserting that no modeling program properly models an inductor?
> The fact that some do not hardly means that all do not. There are plenty
> of low-quality scopes about, but that fact doesn't invalidate the
> measurements made with high-quality ones.
Please tell me the name of one that models a solenoid inductor
properly at radio frequencies. I really would like to purchase a copy.
73, Tom W8JI
w8ji@contesting.com
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