Ed said -
That was back in the days when fantastic claims were settled with a
working
model. If you wanted to argue about the efficiency of a venturi, or the
strength of a gear tooth profile, you built it and then actually used it.
If
your drill bit stayed sharp longer, or you pumped more water with less
coal,
you won your argument.

We spend a lot of time now arguing about how well the computer model
replicates reality, and whether the math has enough variables accounted
for.
Working models seem so old fashioned.

=======================================

It is a fatal mistake to treat a modelling program, even if you think it has
no bugs (errors), as a bible which always tells the gospel truth. ALL
programs have limitations.

Limitations result from the computer itself, those deliberately introduced
by the programmer, those accidentally introduced by the programmer because
he didn't understand how the thing being modelled really works, those
introduced by the user because he doesn't understand how the program is
supposed to work or what the programmer was thinking about when he wrote it.

The result is UNRELIABILITY.

Ideally, the originator of the thing being modelled and the programmer
should be one and the same person. Committies produce drumadaries with 3 or
more humps. Or elephants with trunks at both ends.

The definition of Reliability is Quality versus Time, and therefore
confidence (or lack of it) can be gained only with both use and time.

Given time, and use, with large programs, such statistics as
mean-time-between-failures can be produced. But when the next error might
arise and its magnitude is anybody's guess. One is always caught unawares.
More insidiously, one may not be aware that an error HAS occurred. Or most
insidiously, one may imagine an error has occurred when it hasn't.

Problems will surely persist - if a failure is suspected, is it the program
which has failed, is it the computer, is it the modelling, or is it the
actual thing being modelled (it may not exist) which is defective?

The proof of the pudding lies in the eating. Get off your ass, wrench
yourself away from the keyboard, do what you should have done in the first
place, erect the thing and use an instrument which purports to measure SWR,
hope for the best, don't swear by it, and take care to record the instrument
manufacturer's name and its serial number. ;o)

To summarise, the reliabilty of a modelling program is always worse than the
quality of the blamed programmer. Initially, don't believe anything it
produces.

And whatever you do, don't become depressed. Even if the program doesn't
work the radio will. Most happy-band radio amateurs don't realise how
fortunate they are - almost anything works thank goodness.

At present I'm on Spanish Red, Berberna, Reserva 2000. I know it's Spanish
because, unusually, the entire blurb on the bottle is in that language. But
I feel somewhat guilty because at the back of my mind there's the continuing
unbelievable horror of the enormous disaster in the countries surrounding
the Eastern Indian Ocean. The worst effects may still be to come.
----
Reg, G4FGQ