On Mar 11, 5:10 pm, (Richard Harrison)
wrote:
Art wrote:

"Can you comment on the tilt angle of the radiator to the ground to
achieve max horizontal polarization?"

Vertical radiators over the earth are optimally exactly vertical. Were
it not so, broadcasters would use tillted towers.

An excercise I`ve performed countless times is microwave path
establishment and optimization. I`ve bolted the tiny dipole feed into
the dish selecting horizontal polarization over vertical polarization in
most cases.

To establish a path, I set the azimuth using a transit and Coast and
Geodetic Survey maps to aim the dish on path. To aim for the horizon as
needed for a long path, I simply use a bubble level on the feed horn.

As soon as the signal appears, optimizarion begins by refining azimuth,
elevation, and polarization for maximum limiter current in the receiver.
Never have I seen any adjustment other than azimuth make any change in
the signal received. Parallel antennas at both ends of the path are
optimum. The same is true with vertical polarization for what is
essentially free-space propagation except for the grazing near the
middle of the path.

Tilt as Art implies it is a myth.

Best regards, Richard Harrison, KB5WZI

Richard, You are living in the past. Learn how to use a computor
then use it to learn for yourself so that you can be a worthwhile
contributor instead of a book parrot. First proove it for your self
then share findings that you obtain for yourself.Ofcourse that isn't
going to happen
since you don't want to learn how to use a computor because you hate
change.
If Roy is a friend of yours ask him to check it out on his computor
program or
ask anybody who has a computor to check it for you before mounting
your podium.
with silly statements. Why can't you do that vector trial have you
forgotten
that ol;d electrical stuff? Does old age give you enough license to
live a continual senior moment
for days at a time?

"Cecil Moore" wrote in message
. net...
John KD5YI wrote:
At least you supplied another viewpoint from an authority, although you
go
on to reduce my confidence in the quote with "seems to imply" and "it is
possible" (but not certain).

Those are my guarded words, not Balanis'. :-)
--
73, Cecil http://www.w5dxp.com


Oh, crap, Cecil! I know they were not Balanis' words.

The point was that you did not need to supply your own interpretation of
Balanis' quote ("seems to imply" and "it is possible"). You could have
simply supplied the quote and left it at that just as I did in my original
post in this thread. The apparent intention of your "guarded words" was to
support your own viewpoint with Balanis' quote.

Cheers,
John

On Tue, 11 Mar 2008 11:18:08 -0700, Art Unwin wrote:

15 years ago I stated that radiation is in the form of pulses,all
laughed Since then I have itemised the steps to make the small antenna,
all laughed.

In refutation, the proof.


The info is in the archives many many times but to my knoweledge nobody
has tried it for themselves preferring to memorise what the books say.
Yes it does look like a tuned circuit on the end of a coax but what if
it is?

Actually, if that is what it is, then fine! antennas such as that are
perfectly legit. It will almost certainly use the feedline as a large
part of the radiator. This antenna bears some resemblance to the Isotron
line of antennas. Not for everyone, for sure, but I'm not going to get
into a definition war on what comprises a "good" antenna, at least in
this case..

But unless there is something new going on - and I don't buy claims of
newfangled physics without proofs - especially physics that need to
include apparent ability of comprehension on my part, it is another
radiating feed line antenna, and not much more.


-73 de Mike N3LI -

John KD5YI wrote:
The apparent intention of your "guarded
words" was to support your own viewpoint with Balanis' quote.

Nope, I don't have a dog in this fight.
--
73, Cecil http://www.w5dxp.com

Art wrote:
"Why can`t you do that vector trial have you forgotten that old
electrical stuff?

Not completely but it serves little purpose in this arena. I admit that
being retired for decades requires me at times to search my memory for
awhile to retrieve something stored there but that is where the books
come in as reminders.

Richard Clark noted that "size counts" appears on page 3 of Ed Laport`s
"Radio Antenna Engineering". Richard was right:

"---concerns the field around a very short doublet in free space
composed of a straight conductor of length l in which a sinusoidal
alternating current of frequency f is flowing. The current is assumed
to be uniform throughout the length of this doublet."

The above exerpt is sufficient to show the field around a very short
(elementary) doublet in free space is a function of length l as
previously reported from page 864 of Terman`s 1955 opus. The old masters
agree. So call me a parrot already. I don`t care.

I gave you examples of my experience with microwaves. These showed
antennas with the same polarizatiions have the least path loss.
Polarization diversity in addition to space and frequency diversity has
been used to improve reception and reliability on mivrowave paths. When
one polarization, position, or frequency falters, a switch is
automatically made to the other alternative. Reliability is greatly
improved. Surely other readers have had similar experiences with antenna
alignment to receive the best signal. It requires that the antennas be
parallel. Crossed antenna polarization on line-of-sight paths causes
huge (30 dB?) loss.

FM broadcasting began with horizontally polarized antennas. Automobiles
using vertically polarized antennas required FM broadcasters to add
vertical polarization to serve a mobile audience.

Best regards, Richard Harrison, KB5WZI

I'm a little concerned about the authoritative quotes I've seen lately
which state that the field from a conductor is directly proportional to
the current in the conductor. While true, it's seemingly being used to
support the conclusion that a longer conductor inherently produces a
greater field, and by extension, that a larger antenna fundamentally
radiates more than a smaller one. Those conclusions are false, and I'll
explain why.

It's useful to start with the law of conservation of energy. If an
antenna is lossless, then all the power fed to it must be radiated. This
has to be true regardless of the antenna's size. So how can this be, if
the field is proportional to the conductor length? Are longer conductors
less lossy than short ones?

No, the principle of field being proportional to current and conductor
length assumes zero loss, so it has to apply to small and large antennas
alike. But so does the law of conservation of energy.

The answer to this apparent dilemma is that if you put a fixed *power*
into dipoles, say, of various lengths, the current will increase as the
antenna gets shorter. This keeps the product of length X current
essentially constant, resulting in a nearly constant radiated field for
a fixed power input. Another way of expressing the same thing which
might be more familiar is that the radiation resistance decreases as the
antenna gets shorter. Consequently, the current increases for a given
power input. To look at it yet another way, consider that if all the
power is to be radiated by both a short and long antenna, the current
must be much higher to get the same radiation from a short conductor as
a long one.

This increase in current becomes dramatic when the antenna gets very
small (in terms of wavelength), and that's where one of the problems
lies with short antennas. The I^2 * R conductor loss can become not only
significant but large even with very good conductors, when the antenna
is small. And that's why small antennas are often less efficient than
larger ones. It turns out to be due to the fact that the field is
proportional to the current and conductor length but not for the
simplistic reasons being implied. But the poor efficiency of a small
antenna is a practical matter which can be mitigated, often to a very
great extent, by using large and good conductors for example. It's not
due to any fundamental rule of radiation.

Another reason that looking only at the current - length rule for field
strength can be misleading is that the radiated field is the sum of many
incremental fields from the various parts of the antenna. Some antennas,
such as small loops or a W8JK beam, create fields which fully or
partially cancel in all directions. So the fields generated by the
individual parts of the antennas are greater than they'd otherwise need
to be in order to generate the resulting total radiation field. This
further reduces the efficiency of these antenna types, since higher
currents are being required to generate the larger fields. Still,
though, the law of conservation of energy applies -- except for power
lost to heating, all the power applied ends up in the radiated field,
even if it takes a much larger local (near) field in order to produce it.

There are other consequences of making an antenna small. One is that if
you do succeed in making it efficient by keeping loss very low, the
bandwidth will be very narrow. Another is that the very small radiation
resistance is accompanied by a very high feedpoint reactance. Any
practical network used to match this to the common 50 + j0 ohms required
by most transmitters and receivers will also be likely to be quite lossy
due to very high currents and/or voltages within the network. And, like
the antenna, most reasonably efficient matching networks will tend to be
very narrowbanded when being required to effect such an extreme
impedance transformation.

The considerations above are why small antennas are invariably
narrowbanded, inefficient, or both, and if the matching network loss is
included in the efficiency calculation, virtually never very efficient.
Claims to the contrary are heard all the time. But under scrutiny and
controlled test conditions, they don't fare any better than water dowsing.

Roy Lewallen, W7EL

On Mar 12, 1:54 am, Roy Lewallen wrote:
I'm a little concerned about the authoritative quotes I've seen lately
which state that the field from a conductor is directly proportional to
the current in the conductor. While true, it's seemingly being used to
support the conclusion that a longer conductor inherently produces a
greater field, and by extension, that a larger antenna fundamentally
radiates more than a smaller one. Those conclusions are false, and I'll
explain why.

It's useful to start with the law of conservation of energy. If an
antenna is lossless, then all the power fed to it must be radiated. This
has to be true regardless of the antenna's size. So how can this be, if
the field is proportional to the conductor length? Are longer conductors
less lossy than short ones?

No, the principle of field being proportional to current and conductor
length assumes zero loss, so it has to apply to small and large antennas
alike. But so does the law of conservation of energy.

The answer to this apparent dilemma is that if you put a fixed *power*
into dipoles, say, of various lengths, the current will increase as the
antenna gets shorter. This keeps the product of length X current
essentially constant, resulting in a nearly constant radiated field for
a fixed power input. Another way of expressing the same thing which
might be more familiar is that the radiation resistance decreases as the
antenna gets shorter. Consequently, the current increases for a given
power input. To look at it yet another way, consider that if all the
power is to be radiated by both a short and long antenna, the current
must be much higher to get the same radiation from a short conductor as
a long one.

This increase in current becomes dramatic when the antenna gets very
small (in terms of wavelength), and that's where one of the problems
lies with short antennas. The I^2 * R conductor loss can become not only
significant but large even with very good conductors, when the antenna
is small. And that's why small antennas are often less efficient than
larger ones. It turns out to be due to the fact that the field is
proportional to the current and conductor length but not for the
simplistic reasons being implied. But the poor efficiency of a small
antenna is a practical matter which can be mitigated, often to a very
great extent, by using large and good conductors for example. It's not
due to any fundamental rule of radiation.

Another reason that looking only at the current - length rule for field
strength can be misleading is that the radiated field is the sum of many
incremental fields from the various parts of the antenna. Some antennas,
such as small loops or a W8JK beam, create fields which fully or
partially cancel in all directions. So the fields generated by the
individual parts of the antennas are greater than they'd otherwise need
to be in order to generate the resulting total radiation field. This
further reduces the efficiency of these antenna types, since higher
currents are being required to generate the larger fields. Still,
though, the law of conservation of energy applies -- except for power
lost to heating, all the power applied ends up in the radiated field,
even if it takes a much larger local (near) field in order to produce it.

There are other consequences of making an antenna small. One is that if
you do succeed in making it efficient by keeping loss very low, the
bandwidth will be very narrow. Another is that the very small radiation
resistance is accompanied by a very high feedpoint reactance. Any
practical network used to match this to the common 50 + j0 ohms required
by most transmitters and receivers will also be likely to be quite lossy
due to very high currents and/or voltages within the network. And, like
the antenna, most reasonably efficient matching networks will tend to be
very narrowbanded when being required to effect such an extreme
impedance transformation.

The considerations above are why small antennas are invariably
narrowbanded, inefficient, or both, and if the matching network loss is
included in the efficiency calculation, virtually never very efficient.
Claims to the contrary are heard all the time. But under scrutiny and
controlled test conditions, they don't fare any better than water dowsing.

Roy Lewallen, W7EL

I go along with that but only if you meant electrically small
antennas.
Some of the group confuse electrically small with physically small.
Richard for years has viewed them as being the same despite my
corrections.
Fractional wavelength is electrically small tho some would say it must
be
less than 0.1 WL
Art

On Mar 11, 9:54 pm, Mike Coslo wrote:
On Tue, 11 Mar 2008 11:18:08 -0700, Art Unwin wrote:
15 years ago I stated that radiation is in the form of pulses,all
laughed Since then I have itemised the steps to make the small antenna,
all laughed.

In refutation, the proof.

The info is in the archives many many times but to my knoweledge nobody
has tried it for themselves preferring to memorise what the books say.
Yes it does look like a tuned circuit on the end of a coax but what if
it is?

Actually, if that is what it is, then fine! antennas such as that are
perfectly legit. It will almost certainly use the feedline as a large
part of the radiator. This antenna bears some resemblance to the Isotron
line of antennas. Not for everyone, for sure, but I'm not going to get
into a definition war on what comprises a "good" antenna, at least in
this case..

But unless there is something new going on - and I don't buy claims of
newfangled physics without proofs - especially physics that need to
include apparent ability of comprehension on my part, it is another
radiating feed line antenna, and not much more.

-73 de Mike N3LI -

On a more serious note,
you consistently refer to heating problems or
feed line radiation. Will you be good enough to explain what creates
these
functions and why you can thus refer to them as my problems?
To put things in order.
My antenna does not require a ground system
Electrical WL is alwaysa WL or more in length.
Measurements at the antenna are devoid of reactance at the point of
resonance
Measurements at the transmitter is the same.
Movement away from resonance supplies reactance.
Conformance with Maxwells laws are adhered to.
Now all these facts have been stated many times before, yet you repeat
your views so the actions that create feedline radiation and antenna
melting
problems are totally different to what I understand.
When moving away from the resonant point it provides reactance in
addition to the resistance
All frequencies have more than one resonant point

On Wed, 12 Mar 2008 07:42:54 -0700, Art Unwin wrote:


But unless there is something new going on - and I don't buy claims of
newfangled physics without proofs - especially physics that need to
include apparent ability of comprehension on my part, it is another
radiating feed line antenna, and not much more.

-73 de Mike N3LI -

On a more serious note,
you consistently refer to heating problems or
feed line radiation. Will you be good enough to explain what creates
these functions and why you can thus refer to them as my problems? To
put things in order.

You might have me mixed up with someone else, Art. I have commented on
feedline radiation in this context, but my only posts about heating
problems was with that antenna produced by the U of Delaware in which the
initial press release touted that the original antenna was so efficient
that it burnt up when 100 watts was applied. Subsequently removed from
later text. I don't think that many people would believe that an antenna
that melts is radiating efficiently. Otherwise I only predict that your
feedline likely will radiate, not that it will heat.

My antenna does not require a ground system
Electrical WL is alwaysa WL or more in length. Measurements at the
antenna are devoid of reactance at the point of resonance
Measurements at the transmitter is the same. Movement away from
resonance supplies reactance. Conformance with Maxwells laws are adhered
to. Now all these facts have been stated many times before, yet you
repeat your views so the actions that create feedline radiation and
antenna melting problems are totally different to what I understand.

Sigh... would you like to point out the post(s) where I said all this?

Aside from that, I expect the feedline to radiate.

--
-73 de Mike N3LI -

On Mar 12, 8:22 pm, Mike Coslo wrote:
On Wed, 12 Mar 2008 07:42:54 -0700, Art Unwin wrote:
But unless there is something new going on - and I don't buy claims of
newfangled physics without proofs - especially physics that need to
include apparent ability of comprehension on my part, it is another
radiating feed line antenna, and not much more.

-73 de Mike N3LI -

On a more serious note,
you consistently refer to heating problems or
feed line radiation. Will you be good enough to explain what creates
these functions and why you can thus refer to them as my problems? To
put things in order.

You might have me mixed up with someone else, Art. I have commented on
feedline radiation in this context, but my only posts about heating
problems was with that antenna produced by the U of Delaware in which the
initial press release touted that the original antenna was so efficient
that it burnt up when 100 watts was applied. Subsequently removed from
later text. I don't think that many people would believe that an antenna
that melts is radiating efficiently. Otherwise I only predict that your
feedline likely will radiate, not that it will heat.

My antenna does not require a ground system
Electrical WL is alwaysa WL or more in length. Measurements at the
antenna are devoid of reactance at the point of resonance
Measurements at the transmitter is the same. Movement away from
resonance supplies reactance. Conformance with Maxwells laws are adhered
to. Now all these facts have been stated many times before, yet you
repeat your views so the actions that create feedline radiation and
antenna melting problems are totally different to what I understand.

Sigh... would you like to point out the post(s) where I said all this?

Aside from that, I expect the feedline to radiate.

--
-73 de Mike N3LI -

Well I may have mixed people up. Sorry about that.
What will cause the feedline to radiate given the facts I have
provided?
Art