Why must engineere resort to quoting from their worshipped Guru's who are
hardly more likely to be correct than they are themslves.

That's easy, because most of the time we have no other choice. When designing
circuits, antennas, troubleshooting, or talking to newsgroups, we have to rely
on other's research. There is no way we can experimentally verify all the data
sheets. charts, graphs, computer programs ect. that are available.
Quoting the last 100 years of antenna research, from worshipped Guru's should
not be a bad thing, because most of us will never have the opportunity to prove
them incorrect. I assume many of the Guru's did the research.
Reg, I am sure you have found numerous errors in Guru's texts, and have tried
to point them out to us. But you cant't just go out in the back yard and burn
all those books:-) Who would we then quote?
73 Gary N4AST

Richard Harrison wrote:
Negative resistance is a gain instead of a loss.

Therefore, doesn't an amplifier have negative resistance?
--
73, Cecil

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

Cecil, for once, you are not far from the truth. The problem lies in
producing the equivalent circuit diagram.
----
Reg.

"Reg Edwards" wrote in message
...
Richard Harrison wrote:
Negative resistance is a gain instead of a loss.

Therefore, doesn't an amplifier have negative resistance?
--
73, Cecil

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

Cecil, for once, you are not far from the truth. The problem lies in
producing the equivalent circuit diagram.
----
Reg.


Hey guys,
Jog my memory; but don't some power tubes have a high value negative plate
resistance under some bias conditions and will oscillate under no load
conditions if external losses are low.
The 4CX250 family comes to mind.

Tam/WB2TT

SWCAD from Linear. I also built up a model of an ideal SWR meter.

Tam

"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:
There is no current in the steady state.

There is no *net* current in the steady state at the input of a
shorted 1/4WL stub. What do you think the current at the short
is? How did that large amount of current get there without flowing?
--
73, Cecil http://www.qsl.net/w5dxp


Cecil,
I think it is more instructive to turn on a DC voltage at t=0, rather than a
sine wave. In either case, the voltage builds up step wise, with smaller and
smaller steps until you don't see them.

Tam

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On Wed, 26 May 2004 21:56:04 +0000 (UTC), "Reg Edwards"
wrote:

If nobody knows what the internal impedance of a transmitter
actually is, how do you know it's not conjugate matched? :-)
--------------------------------

Because nobody knows. And it wouldn't make slightest difference to anything
if anyone did.

Lord Kelvinator is mighty proud of you, bucko.

And nobody knows why I keep answering your questions either. ;o)

You didn't answer any question, you responded - big difference.

We at least get the varietal name of the grape you are knocking back.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Tue, 25 May 2004 07:27:03 -0500, "Richard Fry"
wrote:
REALITY CHECK: If tx source Z really was 50 ohms, a tx connected to a 50
ohm load would lose 1/2 of the RF power it generates to that internal Z.

Dear Richard,

This is the time-honored misreading and misapplication of Thevenin's
theorem posed by Edison to confound investors in Westinghouse's AC
generation plants. Look at the ratio of DC to AC power plants
constructed in the past century to find the poor accuracy of your
reading.

73's
Richard Clark, KB7QHC
Richard,
I believe Edison was talking about the Synchronous Impedance of an
alternator. That measurement is based on the short circuit current of the
machine, and limited by the leakage inductance; purposely made large for
self protection. As for pertinent numbers, a 2300V 1000A alternator has an
effective series resistance of about .05 Ohm. That is feeding a load of 2.3
Ohms.

Tam/WB2TT

There is no way we can experimentally verify all the data
sheets. charts, graphs, computer programs ect. that are available.

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

There's no need to. Inevitably, 99.9 percent of data to be found in books
does not match up to the exact problem in hand. And what is in hand is VERY
exact. Very early in one's career one realises this and soon discovers it is
largely a waste of time 'researching' the literature for details. There's
too much of it. It is more expeditious to have confidence in one's ability,
to go back to first principles and THEN concentrate on the details in
and - which are NEVER to be found in the books.

The best engineers don't have time to write books - except perhaps for
short, simple ones which educate by concentrating on first principles. A
relatively few number of such books or papers are needed. Nearly all of
them have already been written. Such as Shannon's beautifully concise paper
on Ball-packing.

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

Quoting the last 100 years of antenna research, from worshipped Guru's
should
not be a bad thing, because most of us will never have the opportunity to
prove
them incorrect.

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

But good engineers accidentally find them incorrect all the time. It forms
part of their normal wasted time. Anybody who worships a book has only ever
read it (e.g. not built the circuit ) - he has never used it in anger. It
has to be admitted that finding more than two errors in a book (not counting
obvious printing errors) is enough to destroy its sacred properties.

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

Reg, I am sure you have found numerous errors in Guru's texts, and have
tried
to point them out to us. But you cant't just go out in the back yard and
burn
all those books:-) Who would we then quote?

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

I once quoted (second hand) from a text book on this newsgroup. But it was
in an ironical context. Probably nobody noticed.

I possess remarkably few books on radio enginering. One of then is a
treasured 1937 copy of Terman's Radio Engineering. I may refer to it once
every few years because of its comprehensiveness. I have a poor memory. But
I wouldn't dream of using numbers from it in anger without checking from
first principles they are in the right ball park. I remember first
principles. They are so simple and can be expressed in plain English.

But I could not bear to see books of any sort burned! Carry on quoting
Kraus who I am a little familiar with via this newsgroup.

The bottle is finished. Good Night.
----
Reg, G4FGQ

Jim Kelley wrote:

Cecil Moore wrote:
So the answer is yes, credit cards are a form of money. Sorry.

A distinction is commonly drawn between plastic and cash, Cecil. I
expected you wouldn't be too stubborn to acknowledge that. My mistake.

Do you happen to have a special dictionary where words don't
mean what words mean? Money can be plastic or cash or gold or
silver or worthless coins or sea shells or virtually any other
medium of exchange.
--
73, Cecil http://www.qsl.net/w5dxp



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Tam/WB2TT wrote:

"Cecil Moore" wrote:
There is no *net* current in the steady state at the input of a
shorted 1/4WL stub. What do you think the current at the short
is? How did that large amount of current get there without flowing?
--
I think it is more instructive to turn on a DC voltage at t=0, rather than a
sine wave. In either case, the voltage builds up step wise, with smaller and
smaller steps until you don't see them.

DC doesn't tell us anything about a 1/4WL shorted stub which is a
network problem, not a circuit problem. The net current at the mouth
of the stub is close to zero while the voltage is at a maximum. At
the short at the other end of the stub, transmission line theory holds.
The voltage is close to zero while the current is at a maximum. Now
exactly how can maximum current be flowing through that short if
no current is flowing into and out of the stub. Hint: it can't!

The forward current and reflected current cancel at the mouth of
the shorted 1/4WL stub. However, they add in-phase 1/4WL away at
the short, maybe to many amps of RF current at the shorted end.
Since there is no physical impedance at the mouth of a stub, nothing
except superposition of forward and reflected waves happens there
and nothing except a virtual impedance exists there. All of the action
is at the shorted end of the stub where there exists 100% reflection.
--
73, Cecil http://www.qsl.net/w5dxp



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