On Sun, 06 Jun 2004 23:18:37 -0500, Cecil Moore
wrote:
Walter Maxwell wrote:
voltage is NOT the forward voltage. If you can't come to realize this is the key
to the problem I'm going to have to give up.

I'm sorry, Walt,
Your belief that V2 is a reflected wave is the root of the misunderstanding.
V2 is a re-reflected wave
Another way of saying "You are right, Walt, you are wrong."

Let's see, you two have passed this SAME thing back and forth 39
times, cannot agree about what each thinks about ONE particular, and
each of you insist you know what a third party meant.

Well, I'm off to Foggy Bottom (D.C.) again to where they do this kind
of thing for a living and call it law. ;-)

Let's see if a week improves this chowder.

73's
Richard Clark, KB7QHC

Richard Clark wrote,

Let's see, you two have passed this SAME thing back and forth 39
times, cannot agree about what each thinks about ONE particular, and
each of you insist you know what a third party meant.

Well, I'm off to Foggy Bottom (D.C.) again to where they do this kind
of thing for a living and call it law. ;-)

Let's see if a week improves this chowder.

73's
Richard Clark, KB7QHC


The triumph of hope over experience.
73,
Tom Donaly, KA6RUH

On 07 Jun 2004 14:02:20 GMT, (Tdonaly) wrote:

Richard Clark wrote,

Let's see, you two have passed this SAME thing back and forth 39
times, cannot agree about what each thinks about ONE particular, and
each of you insist you know what a third party meant.

Well, I'm off to Foggy Bottom (D.C.) again to where they do this kind
of thing for a living and call it law. ;-)

Let's see if a week improves this chowder.

73's
Richard Clark, KB7QHC


The triumph of hope over experience.
73,
Tom Donaly, KA6RUH


Hi Tom,

Well, up to 78 (double my last count) and no further along in this
chowder to confirm your observation (makes me glad I abandoned that
metaphor for excellent Chesapeake Crab Cakes).

The twists and turns in this conversation matched all the roads closed
and diverted around the cathedral during the funeral. -whew-

73's
Richard Clark, KB7QHC

SNIP

Backfin lumps, OM?

73, Dave, N3HE

chowder to confirm your observation (makes me glad I abandoned that
metaphor for excellent Chesapeake Crab Cakes).

SNIP

Richard Clark, KB7QHC

On Sun, 13 Jun 2004 05:34:16 -0400, "David J Windisch"
wrote:
Backfin lumps, OM?
chowder to confirm your observation (makes me glad I abandoned that
metaphor for excellent Chesapeake Crab Cakes).

Hi Dave,

Sorry, but that was too terse.

I wasn't in D.C. but for a short event. It was not long enough to
sample the full gustatorial offerings of the region - if that was the
implication. Also managed to run across a bottle of my favorite Rhum
St. James. (Should'a brought a bottle of that back to read this
thread through its bottom.)

73's
Richard Clark, KB7QHC

Hi, Richard:
The very best crab cakes are made from backfin lumps. Sorta like "tuna" and
"albacore tuna". As for terse-ness, I'm a silent mic.
73, Dave, N3HE

"Richard Clark" wrote in message
...
On Sun, 13 Jun 2004 05:34:16 -0400, "David J Windisch"
wrote:
Backfin lumps, OM?
chowder to confirm your observation (makes me glad I abandoned that
metaphor for excellent Chesapeake Crab Cakes).

Hi Dave,

Sorry, but that was too terse.

I wasn't in D.C. but for a short event. It was not long enough to
sample the full gustatorial offerings of the region - if that was the
implication. Also managed to run across a bottle of my favorite Rhum
St. James. (Should'a brought a bottle of that back to read this
thread through its bottom.)

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Sun, 06 Jun 2004 23:18:37 -0500, Cecil Moore
wrote:
I'm sorry, Walt,
Your belief that V2 is a reflected wave is the root of the misunderstanding.
V2 is a re-reflected wave

Another way of saying "You are right, Walt, you are wrong."

It's a very minor mistake, Richard, and one easily made. If you have
a copy of Dr. Best's QEX article, please feel free to express your
take on this discussion.

Let's see if I can present superposition in ASCII graphics. rho
is the voltage reflection coefficient and tau is the voltage
transmission coefficient. Assume VF1 has a phase angle of zero
degrees. Phase angles are important in the following but since
the system is matched, all phase angles are either at zero degrees
or at 180 degrees at the match point. So a sign change is equivalent
to a 180 degree phase shift.

100W XMTR---50 ohm line---x---1/2WL 150 ohm line---50 ohm load
VF1=70.7V-- VF2=141.4V--
--VR1=0V --VR2=70.7V

According to the rules of superposition, the two voltages incident
upon 'x', VF1 and VR2, can be considered separately and then added.

----------------------------------------------------------------

Breaking VF1 down into its two superposition components yields:

x
|
VF1=70.7V (100W)--|
|-- V1=106.06V (75W)
V3=35.35V (25W)--|
|

VF1 = 70.7V at zero degrees (100W)

V1 = VF1(forward-tau) = 70.7(1.5) = 106.06V at zero degrees (75W)

V3 = VF1(forward-rho) = 70.7(0.5) = 35.35V at zero degrees (25W)

Note that PF1 = 100W = P1 + P3 = 75W + 25W

-----------------------------------------------------------------

Breaking VR2 down into its two superposition components yields.


x
|
|-- VR2=70.7V (33.33W)
V4=35.35V (25W)--|
|-- V2=35.35V (8.33W)
|

VR2 = 70.7V at 180 degrees (33.33W)

V2 = VR2(reverse-rho) = 70.7(-0.5) = 35.35V at zero degrees (8.33W)

V4 = VR2(reverse-tau) = 70.7(0.5) = 35.35V at 180 degrees (25W)

Note that PR2 = 33.33W = P2 + P4 = 25W + 8.33W

-----------------------------------------------------------------

Now, following the rules of superposition:

To get the total forward voltage, add V1 + V2

VF2 = V1 + V2 = 106.06V + 35.35V = 141.4V (133.33W)

To get the total reflected voltage, add V3 and V4

VR1 = V3 + V4 = 35.35V - 35.35V = zero volts (0W)

Note: Dr. Best neglected to mention P3 and P4 in his QEX article.
P3+P4 is the interference joules/sec. They are scalar values.

All voltages are consistent and all powers are consistent.

So, in this matched system, all reflected power is re-reflected:

PF2 = 133.33W = P1 + P2 + P3 + P4 = 75W + 8.33W + 25W + 25W

PF2 = P1 + P2 + (complete constructive interference) = 133.33W

PR1 = P3 + P4 - (complete destructive interference) = zero watts

Note that the voltage forward-rho = (150-50)/(150+50) = +0.5

reverse-rho = (50-150)/(50+150) = -0.5 (180 deg phase shift)
--
73, Cecil http://www.qsl.net/w5dxp



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