dansawyeror wrote:
Below is a link to a site that claims to model coax radiation from a
dipole.

http://www.smeter.net/feeding/feedpowr.php

Please note that the third wire to ground creates the unbalance
that causes feedline radiation. You seem to be confusing cause
and effect. The cause of the feedline radiation is the existence
of that third wire, not SWR. All it proves is that feedline
radiation is caused by that third wire path which unbalances
the source currents.
--
73, Cecil http://www.qsl.net/w5dxp

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If it is true it proves that a driving a "bad" load can cause the coax feedline
to radiate a significant portion of the feed energy. At this point I am not sure
what word to use other then 'bad', but I due intend to perform experiments to
measure and verify what is happening and the model.

Dan

Cecil Moore wrote:
dansawyeror wrote:

Below is a link to a site that claims to model coax radiation from a
dipole.

http://www.smeter.net/feeding/feedpowr.php


Please note that the third wire to ground creates the unbalance
that causes feedline radiation. You seem to be confusing cause
and effect. The cause of the feedline radiation is the existence
of that third wire, not SWR. All it proves is that feedline
radiation is caused by that third wire path which unbalances
the source currents.

dansawyeror wrote:
If it is true it proves that a driving a "bad" load can cause the coax
feedline to radiate a significant portion of the feed energy.

You need to define "bad load". A "bad load" for unbalanced line
is a balanced load, no matter what the impedance. A "bad load"
for balanced line is an unbalanced load, no matter what the
impedance.

The third wire used in the aforementioned software is designed
to unbalance the system, no matter what the impedance.

To illustrate a balanced system, a fourth wire needs to be
added in parallel with and about four inches away from the
third wire. Then compare the currents in the third and fourth
wires under conditions of changing loads.

I due intend to perform experiments to measure and verify what is
happening and the model.

Please feel free to experiment but at least a dozen participants
of this newsgroup already know what is happening and have been
trying to tell you.
--
73, Cecil http://www.qsl.net/w5dxp

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dansawyeror wrote:
If it is true it proves that a driving a "bad" load can cause the coax
feedline to radiate a significant portion of the feed energy. At this
point I am not sure what word to use other then 'bad', but I due intend
to perform experiments to measure and verify what is happening and the
model.

dansawyeror wrote:
Below is a link to a site that claims to model coax radiation from a
dipole.

http://www.smeter.net/feeding/feedpowr.php

We are in a position now to say what is wrong with that program.
Essentially, it violates the conservation of energy principle.

Energy cannot exist as both reflected power and radiated power
at the same time.

If the SWR is 1400:1, the feedline cannot be radiating much
because the reflected power is 99.7% of the forward power
and both are based on differential currents which don't
radiate. That leaves only 0.3% of the power available for
radiating by the feedline.

If 99.9% of the power is radiated by the coax braid, then the
feedline SWR must be very close to 1.6:1 because the ratio of
reflected power to forward power can be no more than 0.1/100.

As with cake, you cannot have your reflected power and radiate
it too. Reflected power plus radiated power cannot add up to
more than the forward power. In fact, Pfor = Pref + Prad
If 50% of the power is radiated by the antenna plus feedline,
then 50% of the power is reflected and the SWR is 5.83:1.
--
73, Cecil, http://www.qsl.net/w5dxp

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Cecil Moore wrote:
If 99.9% of the power is radiated by the coax braid, then the
feedline SWR must be very close to 1.6:1 because the ratio of

Sorry, that should be 1.06:1 instead of 1.6:1.

reflected power to forward power can be no more than 0.1/100.
--
73, Cecil, http://www.qsl.net/w5dxp

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Cecil Moore wrote:

dansawyeror wrote:

If it is true it proves that a driving a "bad" load can cause the coax
feedline to radiate a significant portion of the feed energy. At this
point I am not sure what word to use other then 'bad', but I due
intend to perform experiments to measure and verify what is happening
and the model.

dansawyeror wrote:

Below is a link to a site that claims to model coax radiation from a
dipole.

http://www.smeter.net/feeding/feedpowr.php


We are in a position now to say what is wrong with that program.
Essentially, it violates the conservation of energy principle.

Energy cannot exist as both reflected power and radiated power
at the same time.

If the SWR is 1400:1, the feedline cannot be radiating much
because the reflected power is 99.7% of the forward power
and both are based on differential currents which don't
radiate. That leaves only 0.3% of the power available for
radiating by the feedline.

If 99.9% of the power is radiated by the coax braid, then the
feedline SWR must be very close to 1.6:1 because the ratio of
reflected power to forward power can be no more than 0.1/100.

As with cake, you cannot have your reflected power and radiate
it too. Reflected power plus radiated power cannot add up to
more than the forward power. In fact, Pfor = Pref + Prad
If 50% of the power is radiated by the antenna plus feedline,
then 50% of the power is reflected and the SWR is 5.83:1.

Bear in mind that current flowing in a conductor will always generate a
field. Alternating current flowing in a (straight) conductor will
always generate a radiating electromagnetic field. That radiating field
will convey energy if it is not nulled by another equal and opposite
field. You need to demonstrate that all the fields resulting from all
the currents are nulled in this scenario.

Back into the woodwork.

ac6xg

Jim Kelley wrote:
Bear in mind that current flowing in a conductor will always generate a
field. Alternating current flowing in a (straight) conductor will
always generate a radiating electromagnetic field. That radiating field
will convey energy if it is not nulled by another equal and opposite
field. You need to demonstrate that all the fields resulting from all
the currents are nulled in this scenario.

It is true by definition for ideal coaxial feedlines in which the
radiating fields are 100% nulled by the basic shielded design, i.e.
solid copper outer tubing much thicker than the skin effect depth.
The problem with the program is that the conclusions violate the
conservation of energy principle. It is simply impossible to have
a coax SWR of 1400:1 while radiating 99.9% of the power from the
feedline.
--
73, Cecil http://www.qsl.net/w5dxp


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"Cecil Moore" wrote in message
...
dansawyeror wrote:
Below is a link to a site that claims to model coax radiation from a
dipole.

http://www.smeter.net/feeding/feedpowr.php

Please note that the third wire to ground creates the unbalance
that causes feedline radiation. You seem to be confusing cause
and effect. The cause of the feedline radiation is the existence
of that third wire, not SWR. All it proves is that feedline
radiation is caused by that third wire path which unbalances
the source currents.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil

How wrong would it be to say that the *coax* part of the line doesnt
radiate at all?
I see this as a situation where the *outer shield* of a transmission line
is conducting current that radiates.
It seems that a "balanced" antenna that is comprised of a single
conductor and a L shaped conductor that includes the outer conductor of the
coax, could be fed with a balanced line for modeling.

Jerry

Jerry Martes wrote:

"Cecil Moore" wrote in message
...

dansawyeror wrote:

Below is a link to a site that claims to model coax radiation from a
dipole.

http://www.smeter.net/feeding/feedpowr.php

Please note that the third wire to ground creates the unbalance
that causes feedline radiation. You seem to be confusing cause
and effect. The cause of the feedline radiation is the existence
of that third wire, not SWR. All it proves is that feedline
radiation is caused by that third wire path which unbalances
the source currents.
--
73, Cecil http://www.qsl.net/w5dxp


Cecil

How wrong would it be to say that the *coax* part of the line doesnt
radiate at all?
I see this as a situation where the *outer shield* of a transmission line
is conducting current that radiates.
It seems that a "balanced" antenna that is comprised of a single
conductor and a L shaped conductor that includes the outer conductor of the
coax, could be fed with a balanced line for modeling.

Jerry


What I was taught is that in a properly installed antenna system the
coax will not radiate. If the antenna is not properly matched to the
coax you get current flow along the outside of the coax shield.

Dave WD9BDZ

On Wed, 31 Aug 2005 16:17:42 -0500, "David G. Nagel"
wrote:

What I was taught is that in a properly installed antenna system the
coax will not radiate. If the antenna is not properly matched to the
coax you get current flow along the outside of the coax shield.

Dave WD9BDZ

Please read:

http://www.w2du.com/r2ch21.pdf