my SWR reading
 

Richard Harrison wrote:
Power did not exist at the far end of the line until it was transported
there by the line. The line moved the power from the 1st place to the
2nd place. It moved!

Here's a physical analogy. We light a butane lighter at one
point and observe the flame. We close the lighter and move
to another point 100 yards away. We light the lighter again
and observe the flame. Did me move the flame by 100 yards?
Or did we convert energy into power at one point, then
move the energy source to another point and convert the
energy into power?

If you move watts of power then you should be able to
measure that movement in watts/sec or joules/sec/sec.
Have you ever measured such?
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Cecil, W5DXP wrote:
"Have you ever measured such?"

My Bird Model 43 Instruction book says:
"---designed to measure power flow and load match in 50 ohm coaxial
transmission lines."
I`ve used it many times.

Best regards, Richard Harrison, KB5WZI

my SWR reading
 

Cecil Moore wrote:
Gene Fuller wrote:
If you ever come to the realization that there is a difference between
transient conditions and steady-state conditions, along with the
realization that standing waves are actually useful, ...

Please explain how those waves can exist without energy,
i.e. without joules/sec passing a point.

No waves of power needed, average or not.

Please stop doing that, Gene. You know that I don't believe
in "power waves". What you are trying to deny is that EM
waves contain energy that can be measured at a point in
joules/sec = watts. That argument just won't fly.

Cecil,

I did not say anything that denied that EM waves contain energy.

Where this entire controversy always gets hung up is the difference
between the traveling wave model where the waves go back and forth over
the entire length of the transmission line, and the standing wave model.
In the traveling wave model it is necessary for the wave energy to
traverse back and forth along the entire line. This leads to the
condition where energy is flowing in both directions at the same time at
any given point in the line. In the standing wave model the energy
simply sloshes back and forth within a single half-wave loop. No energy
collisions; no problems at all.

As I have said many times, these are mathematical representations, not
physical "reality". Neither is more correct than the other. No physical
measurement can tell the difference. But it is often useful to use the
most convenient model that does not carry unwanted artifacts and other
baggage.

Oh, by the way, it is not possible to measure energy at a point. Energy
has an extrinsic, not intrinsic, character. It would be educational to
read any good physics text to understand what energy really means and
how conservation of energy laws are constructed.

73,
Gene
W4SZ

my SWR reading
 

"Roy Lewallen" wrote:
All the power produced by the transmitter arrives at the antenna
less whatever is lost as heat in the transmission line.
_________

Roy,

If a transmitter produces r-f power, and a load connected to that
transmitter via a transmission line dissipates any of that r-f power, then
would you not agree that such an r-f transmission line conducts at least
whatever r-f power is dissipated by that load?

And if such a transmission line can conduct power in one direction
(incident), it can also conduct power equally well in the opposite direction
(reflected), until the net result of incident + reflected causes line
failure.

When the Zo of a transmission line matches the Zo of a load at its far end,
then that far-end Z absorbs nearly 100% of the power delivered there by that
transmission line.

If those impedances are not matched, a reflection is generated that may lead
to the real-world, destructive and periodic effects on the transmission line
that I reported from personal experience, earlier in this thread.

RF

my SWR reading
 

Richard Fry wrote:
"Roy Lewallen" wrote:
All the power produced by the transmitter arrives at the antenna
less whatever is lost as heat in the transmission line.
_________

Roy,

If a transmitter produces r-f power, and a load connected to that
transmitter via a transmission line dissipates any of that r-f power, then
would you not agree that such an r-f transmission line conducts at least
whatever r-f power is dissipated by that load?

Of course.

And if such a transmission line can conduct power in one direction
(incident), it can also conduct power equally well in the opposite direction
(reflected), until the net result of incident + reflected causes line
failure.

No.

When the Zo of a transmission line matches the Zo of a load at its far end,
then that far-end Z absorbs nearly 100% of the power delivered there by that
transmission line.

This occurs whether or not there's an impedance match. If I connect my
transmitter to a 50 ohm dummy load via a half wavelength 300 ohm line,
all the transmitter's power (less the line loss) is conveyed via the
transmission line to the load. This is in spite of a 6:1 mismatch at the
load.

If those impedances are not matched, a reflection is generated that may lead
to the real-world, destructive and periodic effects on the transmission line
that I reported from personal experience, earlier in this thread.

In my example, as at any time the load and line aren't matched, there
will be standing waves of voltage and current on the line, which can
lead to line failure. In the example you gave, it was almost certainly
the high current points which caused it. If you'll pick up any
transmission line text, you'll be able to quickly see exactly what happened.

You still haven't explained how these imagined power waves cause
periodic effects. Please re-read my last posting -- is it some kind of
phase angle associated with the power waves, or is there some mechanism
by which they vary with position along the line? I'm looking forward to
your mathematical description of what you think is happening. You can
find mine in any textbook on transmission lines. If you'd like, I can
recommend a half dozen or more.

Roy Lewallen, W7EL

my SWR reading
 

James Barrett wrote:
Hi, I just got my new (used) HF rig, and I strung up a half wave dipole
for 10 meters using 28.4 mhz in my calculations. Several hours later I
am getting an SWR reading of 2:1 at 28.4mhz. Is that pretty good or
should I try to do better?

I appreciate any opinions.

Jim

Jim,

whatever the in and outs as discussed in this thread, if you cut and
resonate at 28.4, have the dipole at a decent height, feed it with
50 ohm coax you should get better than 2:1. Do you know what the
actual resonant frequency of the dipole + feeder is?

As an example I have a ten metre dipole in my loft, some 25 feet
above ground. It resonates at 28.44 at the end of approx 10 metres
of 50 ohm coax, the SWR is 1.4:1 . The bandwidth at 2:1 is 28.25
-28.63. At 2.5:1 it is 28.160-28.760. This is before the ATU, after
the ATU the TX sees from 1:1 to 1.4:1 over the whole of ten metres.
See http://www.radiowymsey.org/FanDipole/FanDipole.html


Charlie.

--
M0WYM
www.radiowymsey.org

my SWR reading
 

Owen Duffy wrote:

SNIP FROM HERE ON UP TO THE OP

The guy is looking for answers to his problem and you lot just want
to massage egos! FFS, give the guy some input and hold back on the
theorising.

Next time the OP has an aerial question he's unlikely to come here :(


--
M0WYM
www.radiowymsey.org

my SWR reading
 

charlie wrote in news:PpmdnSwlVffV47
:

....
As an example I have a ten metre dipole in my loft, some 25 feet
above ground. It resonates at 28.44 at the end of approx 10 metres
of 50 ohm coax, the SWR is 1.4:1 . The bandwidth at 2:1 is 28.25
-28.63. At 2.5:1 it is 28.160-28.760. This is before the ATU, after
the ATU the TX sees from 1:1 to 1.4:1 over the whole of ten metres.

You didn't mention the balun, it is significant.

Owen

my SWR reading
 

Richard Harrison wrote:
Cecil, W5DXP wrote:
"Have you ever measured such?"

My Bird Model 43 Instruction book says:
"---designed to measure power flow and load match in 50 ohm coaxial
transmission lines."
I`ve used it many times.

Would you agree it is indirectly measuring joules/sec
not watts/sec? That would be energy flow.
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Gene Fuller wrote:
In the standing wave model the energy
simply sloshes back and forth within a single half-wave loop. No energy
collisions; no problems at all.

The problem is that it is impossible for EM waves to
do that. An EM wave flows in one direction until it
encounters a physical impedance discontinuity. It
cannot "slosh back and forth" in reality.
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

"Cecil Moore" wrote in message
et...
Richard Harrison wrote:
Cecil, W5DXP wrote:
"Have you ever measured such?"

My Bird Model 43 Instruction book says:
"---designed to measure power flow and load match in 50 ohm coaxial
transmission lines."
I`ve used it many times.

Would you agree it is indirectly measuring joules/sec
not watts/sec? That would be energy flow.
--
73, Cecil http://www.w5dxp.com

actually, its not measure energy or power, its measuring voltage and current
and presenting you with the result of a calculation that represents power.

my SWR reading
 

"Richard Fry" wrote in message
...
"Roy Lewallen" wrote:
All the power produced by the transmitter arrives at the antenna
less whatever is lost as heat in the transmission line.
_________

Roy,

If a transmitter produces r-f power, and a load connected to that
transmitter via a transmission line dissipates any of that r-f power, then
would you not agree that such an r-f transmission line conducts at least
whatever r-f power is dissipated by that load?

And if such a transmission line can conduct power in one direction
(incident), it can also conduct power equally well in the opposite
direction (reflected), until the net result of incident + reflected causes
line failure.

When the Zo of a transmission line matches the Zo of a load at its far
end, then that far-end Z absorbs nearly 100% of the power delivered there
by that transmission line.

If those impedances are not matched, a reflection is generated that may
lead to the real-world, destructive and periodic effects on the
transmission line that I reported from personal experience, earlier in
this thread.

RF

no transmission line conducts power. it conducts moving electrons which are
measured as a current or voltage. power is a figment of our mathematics
that has created a convenient way to take the current and/or voltage and/or
impedance (only 2 of the 3 are needed) and convert them to a measure of
energy flow, or power, that happens to be a nice conceptual way to view
things. we could just as well give up all readings of power and state taht
a transmitter produces 1 amp into a 50 ohm load instead of that it produces
50 watts... the former is more descriptive, the latter is simpler for the
non-engineer.

my SWR reading
 

Cecil Moore wrote:
Gene Fuller wrote:
In the standing wave model the energy simply sloshes back and forth
within a single half-wave loop. No energy collisions; no problems at all.

The problem is that it is impossible for EM waves to
do that. An EM wave flows in one direction until it
encounters a physical impedance discontinuity. It
cannot "slosh back and forth" in reality.

I guess you still cannot get over your fixation on traveling waves. Too
bad; you miss so much when wearing blinders.

73,
Gene
W4SZ

my SWR reading
 

Dave wrote:
"Cecil Moore" wrote:
Would you agree it is indirectly measuring joules/sec
not watts/sec? That would be energy flow.

actually, its not measure energy or power, its measuring voltage and current
and presenting you with the result of a calculation that represents power.

Like I said, it is indirectly measuring power -
by sampling the voltage and current at a fixed
point in a known Z0 environment and performing
some in-phase and out-of-phase phasor additions.

The point is that it is displaying watts at a
*fixed* point, i.e. average joules flowing past
a fixed point in one second. It is the joules
that are flowing, not the watts.
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Dave wrote:
power is a figment of our mathematics

With EM waves, you can say the same thing about
voltage and current. The energy in the photons
has a much more basic relationship to reality.
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Gene Fuller wrote:
I guess you still cannot get over your fixation on traveling waves. Too
bad; you miss so much when wearing blinders.

Sloshing EM energy is only a math shortcut which
violates the laws of physics and exists only in
your mind (and others). Traveling EM waves agree
with the laws of physics and can be observed with
one's own eyes.

When math shortcuts become one's religion, one
has a definite problem.
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Cecil Moore wrote:
Gene Fuller wrote:
I guess you still cannot get over your fixation on traveling waves.
Too bad; you miss so much when wearing blinders.

Sloshing EM energy is only a math shortcut which
violates the laws of physics and exists only in
your mind (and others). Traveling EM waves agree
with the laws of physics and can be observed with
one's own eyes.

When math shortcuts become one's religion, one
has a definite problem.

Cecil,

I will not argue with you about mobile antenna shootouts.

However, I will compare my physics education to yours any day. Which
law(s) of physics do you think I have violated?

8-)

73,
Gene
W4SZ

my SWR reading
 

"Roy Lewallen" wrote:
All the power produced by the transmitter arrives at the antenna
less whatever is lost as heat in the transmission line.

How about a case of a non-resonant transmission line whose Zo equals the
load Z except for a discrete mismatch somewhere in the line? Reflections
from that mismatch will be dissipated in the reverse port termination of a
circulator installed at the input of the line. Clearly not all of the power
available at the output of the circulator arrived at the antenna (less line
loss).

..Unless the line is perfectly matched, there will be repeating points of
high current and of high voltage. Depending on the nature of the conductor
and insulator, either or both of these can cause localized heating. In the
example you gave, the damage is almost certainly caused by high current
rather than high voltage. ...

I agree, and misunderstood your original post.

RF

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Gene Fuller wrote:
However, I will compare my physics education to yours any day. Which
law(s) of physics do you think I have violated?

"Sloshing" EM waves violates the conservation
of momentum principle.

What reverses the momentum of an EM wave at the
point where it starts "sloshing" around when
there is no physical impedance discontinuity?

In terms of optics, how does light energy just
start "sloshing" around in free space when
there is no change in index of refraction in
the medium?

Given Hecht's equation for a light standing wave
in free space, where are the terms that cause
the "sloshing"?
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Cecil Moore wrote:
Gene Fuller wrote:
However, I will compare my physics education to yours any day. Which
law(s) of physics do you think I have violated?

"Sloshing" EM waves violates the conservation
of momentum principle.

What reverses the momentum of an EM wave at the
point where it starts "sloshing" around when
there is no physical impedance discontinuity?

In terms of optics, how does light energy just
start "sloshing" around in free space when
there is no change in index of refraction in
the medium?

Given Hecht's equation for a light standing wave
in free space, where are the terms that cause
the "sloshing"?

Cecil,

That's a good one. I did not know that a transmission line is "free space".

Try again.

73,
Gene
W4SZ

my SWR reading
 

Richard Fry wrote:
"Roy Lewallen" wrote:
All the power produced by the transmitter arrives at the antenna
less whatever is lost as heat in the transmission line.

How about a case of a non-resonant transmission line whose Zo equals the
load Z except for a discrete mismatch somewhere in the line?
Reflections from that mismatch will be dissipated in the reverse port
termination of a circulator installed at the input of the line. Clearly
not all of the power available at the output of the circulator arrived
at the antenna (less line loss).

Certainly if you install a resistor in the line, whether connected to a
circulator or not, some of the power leaving the transmitter won't make
it to the load. I was assuming when I made my statement that no such
objects were placed in the transmission line, and would hope this
condition would be obvious to most readers.

..Unless the line is perfectly matched, there will be repeating points
of high current and of high voltage. Depending on the nature of the
conductor and insulator, either or both of these can cause localized
heating. In the example you gave, the damage is almost certainly
caused by high current rather than high voltage. ...

I agree, and misunderstood your original post.

Roy Lewallen, W7EL

my SWR reading
 

Gene Fuller wrote:
That's a good one. I did not know that a transmission line is "free space".

It doesn't matter what the medium is - EM waves
obey the conservation of momentum principle in
any medium. Your "sloshing" waves violate that
accepted principle of physics. Sorry.
--
73, Cecil http://www.w5dxp.com

my SWR reading
 

Owen Duffy wrote:

SNIP


You didn't mention the balun, it is significant.

Owen

I can't comment on that as I did not make any measurements without a
balun. It was always going to have a balun because I did not want
any significant RF coming down the outside of the coax and causing
interference.

It would be a simple matter for Jim to make a balun like mine and I
imagine he'd get very similar results.



Charlie.

--
M0WYM
www.radiowymsey.org

my SWR reading
 

Cecil Moore wrote:
Gene Fuller wrote:
That's a good one. I did not know that a transmission line is "free
space".

It doesn't matter what the medium is - EM waves
obey the conservation of momentum principle in
any medium. Your "sloshing" waves violate that
accepted principle of physics. Sorry.

Cecil,

This entire thread is silly beyond belief. In any case, no matter how
irrelevant, there is no problem at all in balancing momentum when there
is lots of stuff around. Momentum is a completely useless concept in
this example.

But I will declare you to be the winner. 8-)

73,
Gene
W4SZ

my SWR reading
 

Gene Fuller wrote:
Momentum is a completely useless concept in this example.

Obviously useless for your side of the argument. :-)
--
73, Cecil http://www.w5dxp.com