Standing waves
 

On Sep 22, 8:47*pm, tom wrote:
Art Unwin wrote:
So you are back David ! have you built that four poster antenna yet,
of steel I presume,
for the top band? Hopefully the system of yours is in a state of
equilibrium so you can tell us good things about it. Did you have to
make a ground plane system? They are not needed for a system in
equilibrium

Wow! *No ground system needed for top band. *The AM broadcasters are
going to be all over this. *Art, you are about to become very very rich..
* This overturns every measurement ever made on AM broadcast antenna
arrays. *You should be very proud that hundreds of engineers and their
measurements were wrong.

Again, congratulations.

tom
K0TAR

No congratulations necessary. The methods will be available to all
amateurs when the PTO print out comes about. All of this represents a
different aproach than that taken before me. If it is 90 % in error
where only 10% is useful that's fine by me as it represents an advance
supplied by an amateur who wasn't detered from experimenting by
others.
If I feel that something that is taken for granted is in error just
because an author had it printed in a book I will always step forward
if I feel the emperer does not wear any clothes.
Which of you have the courage to stand along side me knowing full well
your character will be dismantled before the true facts become known?

Standing waves
 

On Tue, 22 Sep 2009 18:12:09 -0700 (PDT), Art Unwin
wrote:

Yes, some university libraries allow access to the public but not for
copies. These must
come from journals at quite high prices. Here you can be a member of a
professional society say IEEE but to get the journals of say antennas
and propagation then you must pay a couple of $100 to have access to
them. This is on top of the fees for the institution and the group
that you are personally a member of which also requires fees.

Ummm... IEEE full membership is now $175/year. Membership in the
Antennas and Progagation group is $24/year.
http://www.ieee.org/web/membership/Cost/dues.html
That's about 4000 pages for the extra $24.

If you are a retired former IEEE member, currently unemployed,
disabled, or are working for only peanuts or stock options, you can
get up to a 50% discount on dues.
http://www.ieee.org/web/membership/Cost/special_circumstances.html

You can see the articles in each past issue at:
http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?puNumber=8

If you're a cheap tightwad non-member, like me, you can buy individual
articles ala carte for $29 each:
http://ieeexplore.ieee.org/guide/g_tools_apo.jsp

If you don't mind just older papers, a member can buy the DVD with
everything from AP-S from 1952-2000:
http://www.ict.csiro.au/aps/cdrom.htm
for $100.

If you're a non-member, you really pay hansomly for the printed
publications.
http://www.ieee.org/portal/cms_docs_iportals/iportals/publications/subscriptions/info/IEEE_Sub_Price_List_2010.pdf
For example, the Antenna and Propagation IEEE Transactions for a year
(12 issues) costs $1,200.



--
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 Clark" wrote
...

I'm glad to see you shed that nonsense about hydraulics. As you
understood that topic far less than RF (which is in itself on very
shaky ground), it wouldn't have done to poison the well.

This poor understanding is quite obvious by your last comment above.

I was absent. You wrote:
"All is exactly the same like in the fluids mechanics.

"Exactly" makes it very, very easy to show how an analogy fails:
Describe the laminar flow in terms of
the Reynolds number for
the interface between RF and a Biconical Antenna
and
the interface between RF and a thin wire Antenna."

Maxwell's math is the same as for fluid:

"Maxwell's equations are simply a re-arrangement of relationships worked
out by Faraday in respect of charge and only verified at low speed.
Maxwell discovered that the relationships could be arranged in a form
which mirrored the mathematical description of a fluid"

In fluid are whirls. The magnetic field is like whirl. But not for all
scientists.
"Maxwell's equations" were wrote by Heaviside.
S*

Standing waves
 

"Dave" wrote
...

"Szczepan Bialek" wrote in message
...

In the Gas Analogy the monopole antena is exactly like the Kundt's
tube.


antennas don't have to be 'in resonance'.... a very short dipole radiates
almost as well as one 1/2 wavelength long... its all in the fields.

In my antenna radiate the end where the voltage is doubled. In your
something alse. What?
S*

Standing waves
 

"Richard Fry" wrote
...
On Sep 22, 3:34 am, Szczepan Bia³ek wrote:

Up to now the acoustic analogy is fully applicable.

Not if one understands the physics of radiation.

Physics of radiation is unknown. Antennas are the nice apparatus to analyse
it.

But it is experimentally proved. Stationary charge - electric field,
Moving charge - magnetic field.

Untrue, and I challenge you to cite any credible experimental data
that you think proves your belief.

Far-field EM radiation is produced only by the current flow on the
antenna, and that radiation contains BOTH the electric and the
magnetic fields.

For me the magnetic field is the illusion.

You may have missed the accurate description posted by Chris, and
pasted below.

"The acceleration of charge in an antenna results almost entirely from
the
applied potential difference at its terminals. The radiated fields
result
from the alternating current effectively passing through the radiation
resistance, and all the other, reactive, fields have no direct effect
on the
radiation resistance, or the component of the current that passes
through it
in phase with the voltage that is developed across it, which together,
of
course, represent the radiated power. The reactive fields affect the
terminal impedance and a large imaginary part can upset the device
trying to
send power into the antenna, but that is more of a system issue. The
alternating current that passes through the radiation resistance is
composed
of charge that moves in time with each RF cycle, accelerating and
decelerating accordingly. The electrostatic field developed between
the
ends of a half-wave dipole reaches its maximum value a quarter of a
cycle
later than the voltage at the drive point so any effect it has on the
charge
in the antenna elements during each cycle must be reactive, and it
doesn't
affect the radiation resistance or the radiated wave."

My description is shorter:
The supply unit sends the voltage pulses (in opposite phase) in the
transmissing line. If such pulses collide the voltage is doubled and the
strong radiation take place. In straight radiator the forward pulse collides
with the reflected. In folded dipoles with that from the other wire.
S*

Standing waves
 

"Cecil Moore" wrote
...
Szczepan Bia³ek wrote:
Each dipole antenna radiate two times the applied frequency, ...

Sorry, 2*sin(2wt) sin(wt)

Here's the question: Is the radiated RF wave in phase
with the standing wave current or in phase with the
standing wave voltage? The radiated RF wave cannot be
in phase with both since they are 90 degrees out of
phase on the standing wave antenna.

In the Gas analogy radiate only the doubled voltage. The doubling take place
in the ends of the two radiators. The two spherical waves are radiated. So
some receiver antennas can work on doubled frequency (Luxembourg effect).
S*

Standing waves
 

"Richard Fry" wrote
...
On Sep 22, 1:44 pm, Szczepan Bia³ek wrote:
If what you are saying were really happening,
an antenna would radiate two times the applied frequency,
but it obviously doesn't.

We do not have the both. But we have the Luxembourg effect. Each dipole
antena radiate two times the applied frequency, The pulses from the ends
are 180 degrees apart.

So then, Szczepan, should transmissions using such antennas, and
expecting to be received on frequency "X" transmit on frequency "X" /
2 ? Note that such is not the reality.

It happened in 1930. The Luxembourg LW were received on MW radio sets.

Some low-level radiation from the transmit antenna may exist at twice
the carrier frequency, but in almost all cases it arises from
insufficient suppression of the 2nd harmonic of, and in the
transmitter.

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

And in NO case is it produced as you describe above.

It is easy to check. Now no vertical LW masts. But everybody has a
horizontal dipole.
S*

Standing waves
 

"Richard Fry" wrote
...
On Sep 22, Szczepan Bia³ek wrote:

But what radiate in 0.05WL dipole? There the
"maximum radiation" is in the transmission line (1/4WL from the end).
The feed point is also in the transmissing line.

Then later the same day he wrote:

The feed point is the part of the transmissing line and not radiate.

Pick one of the above comments, only, Szczepan.

The feed points are terminals of the antenna. On center-fed dipoles
that are 1/2WL or less in length, antenna current is highest at those
terminals.

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.

How long are the folded dipoles and the
loop antennas? Are there the short version?

They can be any length, but some lengths have better input
characteristics and/or more useful radiation patterns than others.

Are a loop antennas 0.05WL?
S*

Standing waves
 

tom wrote:
Note that none of these are particularly close to resonance at the
design frequency.

Yagis do have a resonant frequency but that frequency
is not at the design frequency. At the resonant frequency,
the forward gain and F/B ratio are not optimum. At the
optimum forward gain frequency and/or F/B ratio frequency,
the Yagi, sans matching network, is not resonant.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Standing waves
 

Art Unwin wrote:
On top of that, all the antennas that you point to could all be made
resonant in the right type of environment.

Point is, the Yagi radiation pattern sucks at the resonant
frequency, f(r). When one meets the designed-for radiation
pattern, i.e. gain, F/B ratio, beamwidth, etc., the Yagi is
NOT resonant at the design frequency.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com