Gene Fuller wrote:
Cecil Moore wrote:
If you think a standing wave is a "shortcut", how about showing the
mathematical models that support your position?

I already did, Gene, but here it is again:

forward traveling wave + reverse traveling wave = standing wave

just substitute the appropriate math symbols. There's a
trig identity that corresponds to the above equation.

Take away either the forward traveling wave or the reverse
traveling wave and the standing wave ceases to exist.
There's no valid mathematical model that supports the
position that standing waves can exist with the two
component waves.
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
There's no valid mathematical model that supports the
position that standing waves can exist with the two
component waves.

Sorry, obviously should be "without", not "with".
I'm engaging in March Madness while I'm posting.
Gig 'Um, Aggies!
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
Cecil Moore wrote:
Forward traveling wave + reflected traveling wave = standing wave
What happens to the standing wave when you take away the reflected
wave?

It's a different physical situation.

The two components of the standing wave are the forward traveling
wave and the reverse traveling wave. I guess if the reverse
traveling wave disappears, you can't ignore it anymore, huh?
--
73, Cecil, w5dxp.com

Cecil,

If I cut off one leg I will probably fall over. So what?

Your desperate attempts at evasion are showing. 8-)

73,
Gene
W4SZ

Gene Fuller wrote:
Your desperate attempts at evasion are showing. 8-)

I'm not evading anything, Gene. I assert that a standing
wave cannot exist without its component traveling waves.
I can give any number of examples.

You are the one who refuses to provide just one example
of a standing wave existing without its component
traveling waves so exactly who is evading?
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
Your desperate attempts at evasion are showing. 8-)

I'm not evading anything, Gene. I assert that a standing
wave cannot exist without its component traveling waves.
I can give any number of examples.

You are the one who refuses to provide just one example
of a standing wave existing without its component
traveling waves so exactly who is evading?
--
73, Cecil, w5dxp.com

And I say, "Big deal." You can set up any combination of components you
wish. The physical reality remains exactly the same as that (fully)
represented by the standing wave. You simply cannot derive new reality
by manipulating the math.

73,
Gene
W4SZ

Gene Fuller wrote:
You simply cannot derive new reality by manipulating the math.

But, Gene, that is exactly what you have done. Asserting
that two waves with different equations are the same
*IS* manipulating the math.
--
73, Cecil http://www.w5dxp.com

Roy Lewallen wrote:

David G. Nagel wrote:

If you want a quick lesson in high vswr find a ham with an old tube
transmitter and see if he will hook it up to a mismatched load. The
cherry red plates are the reflected energy being absorbed. Transistors
will just turn to smoke under the same conditions.

Unfortunately, you'd be learning the wrong lesson.

The cherry color is due to the transmitter being loaded with an
impedance it's not designed for, causing the final to run at low
efficiency. You can disconnect the antenna and replace it with a lumped
RC or RL impedance of the same value and get exactly the same result.
Alternatively, you can attach any combination of load and transmission
line which give the same impedance, resulting in a wide variation of
"reflected energy", and get exactly the same result. All that counts is
the impedance seen by the transmitter, not the VSWR on the line or the
"reflected power".

The problem is that the idea of "reflected energy" turning the plates
hot is so easy to understand, that people aren't willing to abandon it
simply because it isn't true.

See http://eznec.com/misc/Food_for_thought.pdf for more.

Roy Lewallen, W7EL

Do us a favor, compute the S-vectors for an incandescent lamp with a linear
filament.
Then follow though with the same for a transmitter, transmission line and a
mismatched load.
You will find that is the reflected S-vector that adds heat to the plate.


--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.Â*Â*
--Schiller

Richard Fry wrote:

"Roy Lewallen" wrote
The problem is that the idea of "reflected energy" turning the plates hot
is so easy to understand, that people aren't willing to abandon it simply
because it isn't true.
_____________

But reflected energy/power does exist.

For an easy example, such reflections are evident in the picture seen on
an analog TV receiver when the match between the transmit antenna and the
transmission connected to it is bad enough.

In analog TV transmit systems with a typical 500+ foot length transmission
line from the tx to the antenna, a 5% reflection from a far-end mismatch
can be quite visible, showing as a "ghost" image that is offset from the
main image as related to the round-trip propagation time of the
transmission line.

RF

Poppycock, TV ghosting is caused by multipath length differences. Calculate
the position ratio and the horizontal scan frequency (15750 Hz is close
enough). That gives you the path length difference; it is generally on the
order of miles (= major terrain features).

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.Â*Â*
--Schiller

wrote:

In rec.radio.amateur.antenna Richard Clark wrote:
On Tue, 13 Mar 2007 16:05:02 GMT, wrote:

The fact that any transmission line and antenna combination can be
replaced with an RLC lumped load at the transmitter output and the
transmitter can't tell the difference is something that a lot of
hams seem to have a problem understanding.

Hi Jim,

Would it be fair to say there are a number of Hams (no need to go into
proportionality, could be equal number) who have difficulties of
understanding with going from lumped, equivalent circuits to antennas
and transmission lines?

The two perspectives are not exclusionary nor mutually incompatible,
only the arguers are.

I'd have to say that as soon as a circuit contains a radiator or a
transmission line the arm waving begins.


Except for less than 1%. In the 1960's that would have been about 5% to
10%, and handwaving will never include Wes Hayward W7ZOI.
--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.Â*Â*
--Schiller

"joseph2k" wrote
Poppycock, TV ghosting is caused by multipath length differences.
Calculate
the position ratio and the horizontal scan frequency (15750 Hz is close
enough). That gives you the path length difference; it is generally on
the
order of miles (= major terrain features).
________________

Analog TV ghosts can be produced within the TV transmit antenna system as
well as by reflections of the transmitted signal in the propagation
environment. I know this from my experience as an RCA Broadcast Field
Engineer, because I've evaluated and corrected many transmit antenna systems
that had been the source of such ghosts.

For example, a reflection from a mismatch between a 1,000 foot long,
air-dielectric transmission line and the TV transmit antenna connected to it
produces a ghost with ~ 2 µs delay from the main image. The active scan
width of an NTSC TV line is about 53 µs, so 2/53 = ~4% of the width of the
screen, or maybe 5% counting overscan. This ghost is easy to see in a
typical TV set/viewing setup.

RF