"Reg Edwards" wrote in message
...


SNIP

I sometimes think that the relatively few engineers between 1790 and 1890
performed greater engineering feats than the many who followed them into
the
present age of electronic and genetic engineering. They devoted the whole
of
their lives to their work.

As for us poor souls, the best we can manage is haggling about imaginary
SWR
and conjugate matches which were all sorted out 120 years back. But it's
all
good fun.

Cheers, Reg.




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.


Ed
wb6wsn

Jack Painter wrote:
"Modeling examples listed below appear to be incorrect for lightning,
similar to how modeling for ocean waves cannot be done in a bathtub and
even a swimming pool does not closely replicate the action of waves in a
large body of water."

OK. Here are full-scale examples. My company had radio towers over much
of the earth. Standard practice was protection of the beacon atop the
tower with a Copperweld ground rod alongside the beacon with its sharp
tip pointed at the sky. No protected beacon was ever damaged by
lightning.

Our company headquarters skyscraper was protected by short air terminals
ringing the perophery of the builsing at short regular intervals. No
lightning damage yet in half a century.

You may say it is squivalent to the fellow who walks into a bar with a
strange contrivance suspended around his neck. Asked what the gadgst
does, the new arrival says: "it`s an elephant whistle". Reply is:
"There`s no elephants around here." New arrival says: "See. It works,
doesn`t it?"

I can assure that there have been plenty of lightning strikes safely
bypassed to ground around the protected people and equipment, just as
Ben Franklin and others have predicted.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote

Jack Painter wrote:
"Modeling examples listed below appear to be incorrect for lightning,
similar to how modeling for ocean waves cannot be done in a bathtub and
even a swimming pool does not closely replicate the action of waves in a
large body of water."

OK. Here are full-scale examples. My company had radio towers over much
of the earth. Standard practice was protection of the beacon atop the
tower with a Copperweld ground rod alongside the beacon with its sharp
tip pointed at the sky. No protected beacon was ever damaged by
lightning.

Our company headquarters skyscraper was protected by short air terminals
ringing the perophery of the builsing at short regular intervals. No
lightning damage yet in half a century.

You may say it is squivalent to the fellow who walks into a bar with a
strange contrivance suspended around his neck. Asked what the gadgst
does, the new arrival says: "it`s an elephant whistle". Reply is:
"There`s no elephants around here." New arrival says: "See. It works,
doesn`t it?"

I can assure that there have been plenty of lightning strikes safely
bypassed to ground around the protected people and equipment, just as
Ben Franklin and others have predicted.

Best regards, Richard Harrison, KB5WZI


Hi Richard, because it is completely unlike you to so widely miss the point,
I question whether I understood your responses correctly. The standard
Franklin rods (with pointed tips) have been completely validated in their
application of safely terminating lightning strikes. Nothing in the new
study repudiates that in any way. It simply finds that a lightning rod of
similar length, thickness and composition but with a rounded or blunt-tip,
has attached lightning that was coming to it's twenty-odd foot area
everytime and missed the nearby Franklin rods everytime. The study clearly
restates what engineers all over the world already know, that Franklin rods
work just fine. But it ADDS that the blunt-tip rods work better, end of
study.

Because lightning is impossible to predict, and often it strikes areas of a
grounding system and building below the lightning rods (evidence is the
Empire State Bldg, which has video showing dozens of strikes bypassing the
Franklin rods), then if an improved rod-tip design is validated, then it is
validated, simple as that. Your experience describing a pointed tip
protecting a radio tower sounds rather simplistic as examples, don't you
agree? Nothing could be easier than attaching lightning to the top of a
tower for Pete's sake. Where lightning rod placement and design becomes
critical, is in areas such as multi-level/shaped building corners,
appurtenances, high explosive and flammable liquid storage, etc. Here, the
best available science is used to describe how many feet apart, at what
elevations, etc the air terminal system must be in order to achieve the
desired level of confidence that no lightning attachment will cause damage
to structures, materials or personnel.

Happy New Year and best wishes,

Jack Painter
Virginia Beach, Virginia

"Reg Edwards" wrote in message
...
Wasn't Franklin that lunatic who used to walk around flying kites in the
middle of thunderstorms?
I've done that, repeated his results and am still hear. Not recommended
though.

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

Jack Painter wrote:
"Modelimg examples cited below appear to be incorrect for lightning,
similar to how modeling for ocean weaves cannot be done in a
bathtub,---."

As far as I know there is one set of rules which rules electrical
phenomena, not rules for weak snd onother set of rules for strong
electricity. Lightning is so stromg that it sometimes seems to play by
its own rules, but it really does not.

Jack`s waves in a bathtub metaphor was particularly ironnic. Franklin`s
experiments proved the electricity he was studying was the same stuff on
whatever scale. He charged Leyden jars from the clouds then used the
stored charge to conduct other experiments with the stored charge as his
contempories were doing. Franklin found that hemp twine was a conductor
of sorts while silk was an insulator.

Irony springs from Jacj`s bathtub metaphor. According to the December
2001 issue of "Modern Maturity":
"Alexander Graham Bell - yes, of telephone fame - also invented the
hydrofoil, a boat that rides on a duchion of air. He tested models of
this invention in his tub."

Best regards, Richard Harrison, KB5WZI

"Dave VanHorn" wrote in message
...
The other devices may have circuits that incidentally radiate a little
noise in the aircraft VHF band.
A broadcast FM receiver almost certainly has an oscillator running by
design, in the band.
Where it lands in the aircraft band, is determined by where it's tuned to.

Ah... you're thinking... FM broadcast range is 88-108MHz... with a 10.7MHz
IF... a high side LO is at ~98-118MHz, easily landing within the aircraft
band (which is... 108-??? MHz, right?).

"Airy R. Bean" wrote in message
...
We have to spend so much time during our own time
in education learning the achievements of past heroes, that
perhaps when our own time comes, we are intellectually
exhausted?

Nah, we're all just becoming specialists. Colleges today have their various
'electrical engineering tracks' where you choose between, e.g., power,
communications, digital logic, etc. -- I think that change come about some
20? years ago now.

We can do our bit in the world of Ham Radio by encouraging
our fellows to dabble in the innards of radios (rather than
by visiting the local emporium in order to buy a rice box
and then returning to the emporium when the "snap crackle
and pop" has gone out of it)

Unfortuately it can be difficult to motivate people to study the innards of
radio when you have to explain to them that a modern cell phone has perhaps
some 100 man years of engineering work in it -- and that any attempt to
apply some of this same technology to amateur radio is going to be met by
protest as well!

---Joel Kolstad

"Ed Price" wrote in message
news:gAdBd.6143$yW5.2@fed1read02...
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.

That's because they're so expensive to build. You'd probably never finish
designing something like a modern RF IC if all you could do was design it on
paper, build it, probe around a little to figure out what it 'really' does,
and repeat.

Likewise, few companies can afford to design the autopilot for a jet without
a great deal of simulation first. :-)

"Joel Kolstad" wrote in message
...
"Dave VanHorn" wrote in message
...
The other devices may have circuits that incidentally radiate a little
noise in the aircraft VHF band.
A broadcast FM receiver almost certainly has an oscillator running by
design, in the band.
Where it lands in the aircraft band, is determined by where it's tuned
to.

Ah... you're thinking... FM broadcast range is 88-108MHz... with a 10.7MHz
IF... a high side LO is at ~98-118MHz, easily landing within the aircraft
band (which is... 108-??? MHz, right?).



The original poster is long gone -- refused any info and advice we gave him
including a list of airlines that prohibit AM/FM radios and other devices
And the FAA stance on the matter
Must have been 50+ responses
So I guess we can put this to bed



--
Caveat Lector