Standing waves
 

On Wed, 23 Sep 2009 19:17:19 +0200, Szczepan Bia?ek
wrote:

If you cannot give us a Reynolds number (something like any mechanical
engineer like Art can do - well, yes, I admit that is an unwarranted
presumption on my part), then you may as well let your boat drift on.

I have onmy shelf the Fluid dynamics by Dr Ludwig Prandtl. Prandtl is a big
name.

Too big to comprehend?

73's
Richard Clark, KB7QHC

Standing waves
 

"Cecil Moore" wrote
...
Szczepan Bia³ek wrote:
In my antenna radiate the end where the voltage is doubled. In your
something alse. What?

Unfortunately, the voltage doubling is accompanied by
transmission line currents at the ends of the antenna
which are known not to radiate. The reason is obvious.

When two currents are equal in magnitude and opposite
in phase, they do not radiate (much) because their fields
engage in destructive interference. These currents
are commonly known as transmission line currents but
also exist at the ends of a dipole as forward and
reflected currents.

When the phases of two currents are equal they engage
in constructive interference and radiate. These currents
are commonly known as antenna currents and exist at
the middle of a dipole

In the middle of todays dipole is the air. Current was in the Hertz'
apparatus.

that is equal to or less than
0.5WL long.

Unfortunately for your theory, since the standing wave
voltage is ~90 degrees out of phase with the standing
wave current (in standing wave antennas), the higher
the standing wave voltage the greater the destructive
interference between the forward and reverse currents,
i.e. the higher the voltage, the lower the radiation.

In one antenna can be only one mechanism.
In my antenna the current radiation is very weak.

Sorry, but that is a simple fact of physics. If you
want the ends of a dipole to radiate, you need to
terminate those ends in the characteristic impedance
of the antenna in order to prevent transmission line
currents on the antenna.

Doubled voltage do the work. Current not.

If one models a 1/2WL dipole with the center 1/4WL part
horizontal and the 1/8WL ends vertical, one will get
a magnitude more horizontal radiation from the center
half of the antenna than vertical radiation from the
vertical half of the antenna. That's easy proof that the
center of a 1/2WL dipole radiates more than the ends.
The vertical radiation is 10 dB down from the horizontal
radiation even though equal lengths of horizontal and
vertical wire exists. Is EZNEC wrong?

Radiation depends on the shape of the ends. Thin vertical wire radiate in
horizontal plane. Tipped (big ball) vertical wire omnidirectional.

Running the above dipole at double the frequency
results in equal currents in each 1/8WL of antenna and
indeed, the vertical radiation equals the horizontal
radiation.

Look at the Kundt's tube. At doubled frequency in the horizontal parts the
new sources (doubled voltage) appear.
The sources on the horizontal wires radiate in all direstion perpendicular
to the wires.

S*

Standing waves
 

On Wed, 23 Sep 2009 08:25:12 -0700, Richard Clark
wrote:

On Tue, 22 Sep 2009 23:59:59 -0700, Jeff Liebermann
wrote:

For example, the Antenna and Propagation IEEE Transactions for a year
(12 issues) costs $1,200.

Or you can go to the library and read (and copy) them for free.

The local Santa Cruz libraries are in serious financial trouble. The
main library has severely limited hours, while the satellite branches
are only open two to five days per week.
http://www.santacruzpl.org/news/2009/jun/09/new-hours-all-branches-effective-july-1-2009/
None of the local libraries stock IEEE AP-S Transactions.

Oh, and yes, If you have access to an engineering library on campus.

I joined the UCSC "Friends of the Library" association in order to
obtain an account. $35 to $60/year.
http://giving.ucsc.edu/giving_detail.php?web_id=631
Most IEEE Transactions are available online from off campus.
http://library.ucsc.edu/gateways/gateways-for-visitors-and-neighbors
Most colleges have similar arrangements. I would also join my alumni
association (Cal Poly, Pomona), which offers similar privileges, but
find the local college more convenient. However, there's a catch.
Most of the online IEEE AP-S Transactions are about a year or more
behind. The various libraries seem to prefer annual subscriptions,
which means most recent issues are often unavailable. If that
happens, I either pay the price of the download (only if desperate),
or borrow an issue from a friend with a subscription.

Oh, and yes, if they let you back on campus..... Sorry, some (Art)
have spit on too many professors.

Most of the stuff is available online. No need to visit the campus.
However, when I do, the real problem is parking. There isn't much
available. Going to the UCSC library is a major expedition for me.

I suspect that Art will be ok at a library, as long as he doesn't
bring his soap box and attract attention by loudly denouncing the
content of the physics, antenna design, or grammar books.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Standing waves
 

On Wed, 23 Sep 2009 10:41:38 -0700, Jeff Liebermann
wrote:

I joined the UCSC "Friends of the Library" association in order to
obtain an account. $35 to $60/year.
http://giving.ucsc.edu/giving_detail.php?web_id=631

I went to re-join. Now it's $75/year.
http://library.ucsc.edu/giving/friends/friends-of-the-library-membership-benefits
Sigh...



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Standing waves
 

"Richard Fry" wrote
...
On Sep 23, 6:05 am, Szczepan Bia³ek wrote:

The Luxembourg effect is only possible if the both ends of the dipole are
"visible". The mast was on the tip top.

The Luxemburg effect is not produced by a dipole.

It was the vertical 1/2WL dipole. The doubled frequency was received in
England (I am not sure).
The same was in Warsaw (but collapsed - now is the monopole mast 1/4WL). The
doubled frequency was received in Austria.


It has been ascribed to be produced in the ionosphere when two very
strong EM waves cross-modulate. More likely it occurs when co-
located, high power transmitters cross-modulate in their output stages
due to coupling between their antennas.

Now you have my description. Which one do you prefer?

Now no vertical LW masts. But everybody has a
horizontal dipole.

A horizontal dipole produces horizontally polarized EM radiation,
which has very high propagation loss for the ground wave.

For this reason vertical polarization is universally used for LW and
MW signals.

Are now vertical dipole masts 1/2WL?

Frequency doubling is at all waves. To observe the frequency doubling the
both ends must have the same possibilities. The vertical dipoles have ends
on difeferent altitudes.
S*

Standing waves
 

Richard Clark wrote:
That's about as useful as saying you do not obtain the maximum miles
per gallon in your car when the ashtray is half full or when the
carpets are at their optimal brushed out nap.

Nope, it's as useful as saying one cannot get the
advertised miles per gallon when one is driving
the car uphill at 80 mph. Miles per gallon is
related to incline and speed. Frequency, gain,
and F/B ratio are related. I surprised you don't
know that.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Standing waves
 

"Richard Fry" wrote
...
On Sep 23, 6:14 am, Szczepan Bia³ek wrote:

Highest antenna current do not means high enough to radiate. The high
current is in transmissing line of the short antennas.
. In 0.05 no currents at all at the feed point

If there is no current at the feedpoint terminals of a 0.05WL dipole
then there is no current anywhere else in it, and there would be no
radiation. Obviously that is not the reality.

The simplest dipole is a transmissing line (the two wires).The standing
waves are always 1/2WL apart. The max current is always 1/4WL from the
standing waves. " In 0.05 no currents at all at the feed point" means, of
course, that the current is very very small.

The current distribution in such short dipoles is triangular in form:
highest at the center, and zero at the ends of the dipole arms.

No such oddity in the reality.
S*

Standing waves
 

On Wed, 23 Sep 2009 10:41:38 -0700, Jeff Liebermann
wrote:

Oh, and yes, if they let you back on campus..... Sorry, some (Art)
have spit on too many professors.

Most of the stuff is available online. No need to visit the campus.
However, when I do, the real problem is parking. There isn't much
available. Going to the UCSC library is a major expedition for me.

Hi Jeff,

For me, its a short ride on one bus. I'm on campus twice a week. As
an Alumni, I get library privileges.

I suspect that Art will be ok at a library, as long as he doesn't
bring his soap box and attract attention by loudly denouncing the
content of the physics, antenna design, or grammar books.

He would be lost in the din of the LaRouche crowd (although he might
fit in with them their Coriolis politics).

73's
Richard Clark, KB7QHC

Standing waves
 

On Sep 23, 1:12*pm, Szczepan Bia³ek wrote:

" In 0.05 no currents at all at the *feed point" means, of
course, that the current is very very small.

However small it is, it is still the greatest current value that
exists on that dipole.

RF wrote:
The current distribution in such short dipoles is triangular in form:
highest at the center, and zero at the ends of the dipole arms.

S* answered:
No such oddity in the reality.

No matter how short a dipole antenna is in wavelengths, current is
always zero at the ends of each arm of that dipole.

The current distribution on a thin, wire dipole takes the form of a
sine wave. If the antenna is short, as in this case, then the only
part of the sine that can exist is nearly linear. Hence the
~triangular shape for the total current on the dipole.

Confirm this for yourself using Figure 2-2(b) on page 2-4 of the
following link.

http://books.google.com/books?id=xTS... tenna&f=false

RF

Standing waves
 

On Sep 23, 12:41*pm, Jeff Liebermann wrote:
On Wed, 23 Sep 2009 08:25:12 -0700, Richard Clark
wrote:

On Tue, 22 Sep 2009 23:59:59 -0700, Jeff Liebermann
wrote:

For example, the Antenna and Propagation IEEE Transactions for a year
(12 issues) costs $1,200.

Or you can go to the library and read (and copy) them for free. *

The local Santa Cruz libraries are in serious financial trouble. *The
main library has severely limited hours, while the satellite branches
are only open two to five days per week.
http://www.santacruzpl.org/news/2009/jun/09/new-hours-all-branches-ef...
None of the local libraries stock IEEE AP-S Transactions.

None of the public libraries in Illinois stock them either





Oh, and yes, If you have access to an engineering library on campus.

I joined the UCSC "Friends of the Library" association in order to
obtain an account. *$35 to $60/year. *

Now that is interesting!
Visitors can only get on line if the University have them on their
list as being invited
Time period 45 days. I understand that you can't get copies because of
copywrite laws and oversite by the societies so I assume they get
freebees.
There is some pressure on lab schools to place results on the web
since it is public money. The Governor signed a bill a little while
ago on transparency as to where the money goes
But then nobody actually follow all the laws in Chicago and down
state.


http://giving.ucsc.edu/giving_detail.php?web_id=631
Most IEEE Transactions are available online from off campus.
http://library.ucsc.edu/gateways/gateways-for-visitors-and-neighbors
Most colleges have similar arrangements. *I would also join my alumni
association (Cal Poly, Pomona), which offers similar privileges, but
find the local college more convenient. *However, there's a catch.
Most of the online IEEE AP-S Transactions are about a year or more
behind. *The various libraries seem to prefer annual subscriptions,
which means most recent issues are often unavailable. *If that
happens, I either pay the price of the download (only if desperate),
or borrow an issue from a friend with a subscription.

Oh, and yes, if they let you back on campus..... *Sorry, some (Art)
have spit on too many professors.

Most of the stuff is available online. *No need to visit the campus.
However, when I do, the real problem is parking. * There isn't much
available. *Going to the UCSC library is a major expedition for me.

I suspect that Art will be ok at a library, as long as he doesn't
bring his soap box and attract attention by loudly denouncing the
content of the physics, antenna design, or grammar books.

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558