Tom Bruhns wrote:
Ah, we started out with exact geometric relationships that defined
precise points, and now we're down to 20% accuracy being OK.

Nope, we started out with a simple rule-of-thumb and here it is:

Originating the thread, alhearn wrote:
Why does the reactance peak occur slightly earlier than
half-wavelength?

I responded:
Since the monopole is purely resistive around 1/4WL and
around 1/2WL, i.e. the reactance is zero at those two
points, it is simply impossible for it to be be any
other way.

Sure looks like a simple relatively innocent rule-of-thumb to me.
Absolutely nothing said about exact geometric relationships that
define precise points. You then caused the thread to wander in
the direction of 0.0000000003 accuracy while I was thinking 20%.

I've looked back over my postings and I didn't explicitly state
what I was thinking. I thought it was implicit but I didn't explain my
differentiation between the value of maximum reactance for a dipole Vs
the value of maximum reactance for the SWR circle. My rule-of-thumb is
that they are close enough to being the same point, that for ballpark
conceptual visualization, they can be thought of as being the same point.
I apologize for not being clear on that point. It took me some time to
realize that extreme accuracy was the cornerstone of your argument
against my rule-of-thumb statements.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil, as an engineer of a few years experience you should know that a
scientist can never be allowed to build a bridge ... it will never be
finished because you can never close the flex seams that are used for
thermal expansion/contraction. While engineers finish the job by getting
close enough to walk/drive off.

In a more general tone for the general reader of the list. All
engineering/science deals with tolerances. Engineers accept close enough
to specifications. Scientists want to understand why another significant
digit after the decimal point is not relevant!! :-0

Deacon Dave, W1MCE

I've managed both engineers and applied scientists in my 40+ years of
engineering design. Both disciplines have much to offer.

+ + +

Cecil Moore wrote:

Tom Bruhns wrote:

Ah, we started out with exact geometric relationships that defined
precise points, and now we're down to 20% accuracy being OK.


Nope, we started out with a simple rule-of-thumb and here it is:

Originating the thread, alhearn wrote:

Why does the reactance peak occur slightly earlier than
half-wavelength?


I responded:

Since the monopole is purely resistive around 1/4WL and
around 1/2WL, i.e. the reactance is zero at those two
points, it is simply impossible for it to be be any
other way.


Sure looks like a simple relatively innocent rule-of-thumb to me.
Absolutely nothing said about exact geometric relationships that
define precise points. You then caused the thread to wander in
the direction of 0.0000000003 accuracy while I was thinking 20%.

I've looked back over my postings and I didn't explicitly state
what I was thinking. I thought it was implicit but I didn't explain my
differentiation between the value of maximum reactance for a dipole Vs
the value of maximum reactance for the SWR circle. My rule-of-thumb is
that they are close enough to being the same point, that for ballpark
conceptual visualization, they can be thought of as being the same point.
I apologize for not being clear on that point. It took me some time to
realize that extreme accuracy was the cornerstone of your argument
against my rule-of-thumb statements.

Dave Shrader wrote:
Cecil, as an engineer of a few years experience you should know that a
scientist can never be allowed to build a bridge ... it will never be
finished because you can never close the flex seams that are used for
thermal expansion/contraction. While engineers finish the job by getting
close enough to walk/drive off.

There's a dirty little engineering secret in there, Dave. If you don't
give the engineer a budget and a deadline, he will keep on improving his design
forever. It's the operations (profit) arm of a company that forces the engineer
to give up and say it's close enough. Engineers are just low-paid scientist
wanabees. If engineers had the same dollar/time budget as the scientists, you
wouldn't be able to tell the difference in them except maybe in the level of
performance. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 27 Mar 2004 14:25:35 -0600, Cecil Moore
wrote:

Richard Clark wrote:
The plural "you" is inclusive, which is still a miss-attribution.
This compounds the error.

Not necessarily, Richard.

Necessarily. Your obfuscation compounds the error further.

Richard Clark wrote:

wrote:

Richard Clark wrote:
The plural "you" is inclusive, which is still a miss-attribution.
This compounds the error.

Not necessarily, Richard.

Necessarily. Your obfuscation compounds the error further.

Foxnews reports that you contradicted yourself under oath. Why
should we bother paying attention to anything you have to say?
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 27 Mar 2004 17:40:17 -0600, Cecil Moore
wrote:

Necessarily. Your obfuscation compounds the error further.

Foxnews reports that you contradicted yourself under oath. Why
should we bother paying attention to anything you have to say?

Just goes to show ya, you don't know how to spell either.

Wait a flippin minute, Cecil!!

Cecil Moore wrote:

SNIP


There's a dirty little engineering secret in there, Dave. If you don't
give the engineer a budget and a deadline, he will keep on improving his
design
forever. It's the operations (profit) arm of a company that forces the
engineer
to give up and say it's close enough.

SNIP

I served as Chief Engineer on a major component of the USAF MX Missile
{AKA Peacekeeper S-118] and I'm proud to claim that successful
engineering includes meeting all requirements of the following equally
weighted factors:

1) Meet ALL specifications.
2) Meet them on time.
3) Meet them below budget.

In six years I never requested a waiver to specification, delivered all
assets to the USAF typically 30 to 60 days ahead of schedule and
completed all engineering tasks at 96% to 97% of authorized budget.

Now, to give Cecil his due, the VP of Operations was intensely involved
because the contract incentives, increased profit, was based on ALL
THREE of these criteria.

Moral: Engineering includes technical, schedule and profit performance.
Science advances the knowledge in technical fields while the cost and
schedule issues are subordinate to the profit motive.

Deacon Dave, W1MCE

Dave Shrader wrote:

Wait a flippin minute, Cecil!!

Cecil Moore wrote:
There's a dirty little engineering secret in there, Dave. If you don't
give the engineer a budget and a deadline, he will keep on improving
his design
forever. It's the operations (profit) arm of a company that forces the
engineer to give up and say it's close enough.

1) Meet ALL specifications.
2) Meet them on time.
3) Meet them below budget.

Now, to give Cecil his due, the VP of Operations was intensely involved
because the contract incentives, increased profit, was based on ALL
THREE of these criteria.

Heh, heh, Dave, I think you just proved my point. :-) If you had no time
or budget constraints, would you ever be 100% satisfied with any design?
I wouldn't.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Dave Shrader wrote:

snip for brevity, not for slight

Heh, heh, Dave, I think you just proved my point. :-) If you had no time
or budget constraints, would you ever be 100% satisfied with any design?
I wouldn't.
--
73, Cecil http://www.qsl.net/w5dxp


Neither has Porsche been satisfied.
I offer as evidence the 911. My new C4S is better than my last C4.
So, when is somebody going to make a receiver better than my 75S3B?
73
H.

OB On antennas.
Bought a couple of the Hi-Q motorized babies, the little one and the BIG
(160) one.
Really beautiful work. Art, really. Just gorgeous. But.
The little one shows 33 ohms at resonance on 20.
Returning the BB3 to the Durango, I measure 9 ohms.
hmmmm...
A little checking and, yup, ~10db better with the BB3. ON 20!!
On the Vintage Side Band net today, my ~100 watt S-Line and the BiggIR on
the aluminum roof compared well with the Nott BB3 and the 200 watt TS480 in
the truck. I'm using a toroidal autoformer to match the 9 ohms giving ~50
ohms at resonance.
The Tarheel is about -6db from the Nott. It's a 20 ohm load on 20.
ON 20!!
Not on 80. They're comparable there; Coil losses dominate. The Tarheel is
better built I think.
Amazing what 10x more conduction electrons will do (The Nott's COPPER).
OTOH this configuration I have is 80 - 20 only.

This is all on 20 meters, mind you.
The impedance measurements......
I keep saying that.......

On 80 and 160 (duh) the Hi-Q should win, while the Tarheel on 80 offers the
easiest automation.
I think a 4" diameter screwdriver, oops, that was the first 160 DXCC wasn't
it?

Nobody builds everything I want.
Oh well
73 all

H.








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o Any smooth impedance curve plotted on a
Smith chart will have maximum reactance
at a point on the curve which is tangent
to a constant-reactance curve on the
chart, or which lies at an end of the
impedance curve. Call the impedance at
the point of maximum reactance Zm.

o Clearly, it will be easier to see the
maximum-reactance point if you simply
plot the reactance versus the
independent variable (such as frequency).

o If the maximum reactance is at such a
tangency on a Smith chart, the point of
tangency will be independent of the
reference impedance to which the chart
is plotted.

o In general, the maximum-reactance point
on a constant-SWR circle which passes
through Zm will not be at Zm. Call the
point of maximum reactance on that
constant-SWR circle Zs.

o If you change the reference impedance to
which the Smith chart is scaled, clearly
Zm will still be the maximum reactance
point on the impedance curve. However,
Zm will in general have a different SWR,
and the maximum-reactance point on the
new constant-SWR circle which passes
through Zm will in general be different
from Zs.

o In other words, the SWR circles are useless
for finding the maximum-reactance point on
the impedance curve.

Example: Zm = 1000+j800 ohms
Ref. Impedance: 50 ohms: SWR = 32.82; Zs for that circle = 821.25+j819.73
Ref. Impedance: 300 ohms: SWR = 5.59; Zs for that circle = 865+j811.31
Ref. Impedance: 600 ohms: SWR = 3.; Zs for that circle = 1000+j800

(The 600 ohm case illustrates that there is no requirement that Zs and Zm differ.)


We now return you to your regularly-scheduled obfuscation.