Cecil Moore wrote:

Jim Kelley wrote:
Seems to me it just implies that current at the end of a dipole isn't
really zero.

The net current is very close to zero because the forward and reflected
currents are very nearly equal and 180 degrees out of phase.

Is that what you meant by:

"For that general assumption to be true, the reflected current would
have
to equal the forward current on a standing-wave antenna. But we know it
doesn't"?

It's not clear whether you're making this point in recognition of the
fact that wires are not lossless, or whether you're claiming it's
somehow fundamental to the performance of a radiator.

I think it may actually make many round trips. There may be multiple
reflections.

Of course, but like a transmission line, there is only one forward wave
and one reflected wave. All the multiple reflections are contained in
those two waves.

Then apparently you've decided not to completely eschew making at least
some steady state assumptions. Seductive indeed. ;-)

73, Jim AC6XG

Jim Kelley wrote:
Cecil Moore wrote:
The net current is very close to zero because the forward and reflected
currents are very nearly equal and 180 degrees out of phase.

This is at the tip end of a dipole.

Is that what you meant by:

"For that general assumption to be true, the reflected current would
have
to equal the forward current on a standing-wave antenna. But we know it
doesn't"?

This is apparently not at the tip end of a dipole.

It's not clear whether you're making this point in recognition of the
fact that wires are not lossless, or whether you're claiming it's
somehow fundamental to the performance of a radiator.

Both, radiation is a "loss".

Of course, but like a transmission line, there is only one forward wave
and one reflected wave. All the multiple reflections are contained in
those two waves.

Then apparently you've decided not to completely eschew making at least
some steady state assumptions. Seductive indeed. ;-)

There are only two possible directions, forward and reverse, in which
energy can flow. Multiple reflections do not create any more directions.
I am not opposed to the steady-state solution and use it all the time. I am
opposed to people being seduced by the steady-state solution into believing
there is not such thing as forward and reflected waves even though standing
waves require forward and reflected waves.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Cecil Moore wrote:
I am
opposed to people being seduced by the steady-state solution into believing
there is not such thing as forward and reflected waves even though standing
waves require forward and reflected waves.

I also apologize if this particular dose of reality brought this thread to
a screeching halt.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Cecil Moore wrote:
I am
opposed to people being seduced by the steady-state solution into believing
there is not such thing as forward and reflected waves even though standing
waves require forward and reflected waves.

Say that in Sacramento, and some knucklehead legislator will pass a law
against it.

73, Jim AC6XG

Cecil, W5DXP wrote:
"There are only two possible directions, forward and reverse in which
energy can flow. Multiple reflections do not create any more
directions."

True. Further, all the same-frequency, same-direction signals merge. So,
as Cecil said, there are only two same-frequency signals on a
transmission line, forward and reverse. The interference pattern these
signals produce does not represent another signal.

Trying to use ordinary circuit analysis on standing-wave antennas is
problematic, but it`s been tried in this thread. Here is what R.W.P.
King wrote in "Transmission Lines, Antennas, and Wave Guides", King,
Mimno, and Wing, 1945, on page 86:
"Inductance and capacitance as used in near-zone circuits with uniform
current cannot be defined, and ordinary circuit analysis does not
apply." This has not stopped efforts in this thread to analyze LC
circuits as if we were dealing with low frequencies.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:

Cecil, W5DXP wrote:
"There are only two possible directions, forward and reverse in which
energy can flow. Multiple reflections do not create any more
directions."

True. Further, all the same-frequency, same-direction signals merge. So,
as Cecil said, there are only two same-frequency signals on a
transmission line, forward and reverse. The interference pattern these
signals produce does not represent another signal.

So the claim is that the amplitude of the reflection being bandied about
is the sum of multiple reflections? I haven't seen any indication of
that. It appears to be simply the amplitude of the first reflection.
At least, that's the way it appears to me, the uninitiated.

73, Jim AC6XG

Jim Kelley wrote:
So the claim is that the amplitude of the reflection being bandied about
is the sum of multiple reflections? I haven't seen any indication of
that. It appears to be simply the amplitude of the first reflection.
At least, that's the way it appears to me, the uninitiated.

Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
reflected power is a constant 100W (sans modulation and noise).
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Cecil Moore wrote:

Jim Kelley wrote:
So the claim is that the amplitude of the reflection being bandied about
is the sum of multiple reflections? I haven't seen any indication of
that. It appears to be simply the amplitude of the first reflection.
At least, that's the way it appears to me, the uninitiated.

Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
reflected power is a constant 100W (sans modulation and noise).

Interesting reference. Wish I had it. He's showing re-reflections from
a Z0-matched source? I don't think I understand all I know about that.
:-)

73, AC6XG

On Tue, 18 Nov 2003 13:52:04 -0800, Jim Kelley
wrote:

|
|
|Cecil Moore wrote:
|
| Jim Kelley wrote:
| So the claim is that the amplitude of the reflection being bandied about
| is the sum of multiple reflections? I haven't seen any indication of
| that. It appears to be simply the amplitude of the first reflection.
| At least, that's the way it appears to me, the uninitiated.
|
| Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
| Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
| source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
| 196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
| reflected power is a constant 100W (sans modulation and noise).
|
|Interesting reference. Wish I had it.

I have it and it doesn't say anything of the sort.

|He's showing re-reflections from
|a Z0-matched source? I don't think I understand all I know about that.
|:-)
|
|73, AC6XG

Jim Kelley wrote:
Interesting reference. Wish I had it. He's showing re-reflections from
a Z0-matched source? I don't think I understand all I know about that.

Nope, the reference is a DC transient buildup to steady-state but the
same principles apply to RMS values.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----