The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

Let's kick them around.

Cheers,
John KD5YI

John S wrote:
The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

It does.

Let's kick them around.

There is nothing to kick around unless you want to argue about whether
the various NEC implementations provide valid results.

What NEC will tell you is that as the .5 wave dipole gets shorter and
shorter, the resistive part of the antenna impedance decreases and the
capacitive part increases and the patern and maximum gain changes very
slightly.

As the ratio of resistive input impedance to the wire resistance get
smaller, the I^2R losses increase.

But don't let that stop you from doing it.

People often learn much better from actual doing then they do from lectures.

BTW, you have to pay some attention to segmentation and as you get smaller
and smaller the segmentation limits just how accurate the simulation is.



--
Jim Pennino

On 10/10/2014 1:50 PM, wrote:
John S wrote:
The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

It does.

Let's kick them around.

There is nothing to kick around unless you want to argue about whether
the various NEC implementations provide valid results.

No. I do not want to argue. If you do not want to participate, please
feel free to not post in this thread. I'm sure that your knowledge will
be gratefully accepted when you post if you can do so in a gentlemanly
manner.

What NEC will tell you is that as the .5 wave dipole gets shorter and
shorter, the resistive part of the antenna impedance decreases and the
capacitive part increases and the patern and maximum gain changes very
slightly.

Not concerned about the pattern.

As the ratio of resistive input impedance to the wire resistance get
smaller, the I^2R losses increase.

Yes, of course. Which changes faster?

But don't let that stop you from doing it.

I have never let other people's opinions stopped me from exploring and
learning.

People often learn much better from actual doing then they do from lectures.

True. Today, however, it is nice to be able to explore so many
configurations without spending a lifetime of climbing trees or erecting
support poles or installing towers, or....

BTW, you have to pay some attention to segmentation and as you get smaller
and smaller the segmentation limits just how accurate the simulation is.

I know how that is done. Is this information for me or the other readers?

"John S" wrote in message
...

No. I do not want to argue. If you do not want to participate, please feel
free to not post in this thread. I'm sure that your knowledge will be
gratefully accepted when you post if you can do so in a gentlemanly
manner.


A great pity that you did not apply the same to yourself when
contributing to my thread about the medium.

John S wrote:
On 10/10/2014 1:50 PM, wrote:
John S wrote:
The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

It does.

Let's kick them around.

There is nothing to kick around unless you want to argue about whether
the various NEC implementations provide valid results.

No. I do not want to argue. If you do not want to participate, please
feel free to not post in this thread. I'm sure that your knowledge will
be gratefully accepted when you post if you can do so in a gentlemanly
manner.

A bit sensitive, are we?

What NEC will tell you is that as the .5 wave dipole gets shorter and
shorter, the resistive part of the antenna impedance decreases and the
capacitive part increases and the patern and maximum gain changes very
slightly.

Not concerned about the pattern.

You should at least be concerned about the maximum gain if for no other
reason than to address claims that very short antennas "do not perform".

As the ratio of resistive input impedance to the wire resistance get
smaller, the I^2R losses increase.

Yes, of course. Which changes faster?

I can't say as I have never plotted the data but it would be informative
if you were to do so if you are going to do this.

I would think a plot of I^2R loss versus length in wavelength for at
least two different wire sizes would be instructive, e.g. #8 and #18.

But don't let that stop you from doing it.

I have never let other people's opinions stopped me from exploring and
learning.

People often learn much better from actual doing then they do from lectures.

True. Today, however, it is nice to be able to explore so many
configurations without spending a lifetime of climbing trees or erecting
support poles or installing towers, or....

Yes, simulations prevent a lot of wasted effort.

I once got a hare brained idea for an antenna and modeled it first.

It turned out to be easy to construct with good gain, but an input impedance
in the order of an Ohm and impractical to feed.

Oh well...

BTW, you have to pay some attention to segmentation and as you get smaller
and smaller the segmentation limits just how accurate the simulation is.

I know how that is done. Is this information for me or the other readers?

For whoever is not aware that such limitations exist.


--
Jim Pennino

On 10/10/2014 1:50 PM, wrote:
John S wrote:
The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

It does.

Let's kick them around.

There is nothing to kick around unless you want to argue about whether
the various NEC implementations provide valid results.

What NEC will tell you is that as the .5 wave dipole gets shorter and
shorter, the resistive part of the antenna impedance decreases and the
capacitive part increases and the patern and maximum gain changes very
slightly.

As the ratio of resistive input impedance to the wire resistance get
smaller, the I^2R losses increase.

But don't let that stop you from doing it.

People often learn much better from actual doing then they do from lectures.

BTW, you have to pay some attention to segmentation and as you get smaller
and smaller the segmentation limits just how accurate the simulation is.

Ok, I guess I had hoped to have a good conversation concerning the subject.

Jim has convinced me that it is not a worthwhile effort.

Cheers.

John S wrote:
On 10/10/2014 1:50 PM, wrote:
John S wrote:
The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

It does.

Let's kick them around.

There is nothing to kick around unless you want to argue about whether
the various NEC implementations provide valid results.

What NEC will tell you is that as the .5 wave dipole gets shorter and
shorter, the resistive part of the antenna impedance decreases and the
capacitive part increases and the patern and maximum gain changes very
slightly.

As the ratio of resistive input impedance to the wire resistance get
smaller, the I^2R losses increase.

But don't let that stop you from doing it.

People often learn much better from actual doing then they do from lectures.

BTW, you have to pay some attention to segmentation and as you get smaller
and smaller the segmentation limits just how accurate the simulation is.

Ok, I guess I had hoped to have a good conversation concerning the subject.

Jim has convinced me that it is not a worthwhile effort.

Cheers.


On the contrary, I think it is quite a worthwile effort especially if
you summarize and publish the results for the benefit of all the arm
wavers saying things like "short antennas are poor radiators".

Then you can discuss real data instead of arguing about what some naif
pulled out of his ass.


--
Jim Pennino

On Fri, 10 Oct 2014 20:08:51 -0000, wrote:
(...)

This group is the only one that I read where topic drift ocurrs almost
immediately, often on the first or second followup posting. In other
groups, it usually takes 5 to 7 messages in a thread to produce the
same result. The problem is that everyone (including me) tends to
post about things that they are familiar with, know something about,
or are passionate about the topic (even if they know nothing about
it). If the initial question or request for comments does not fit
these criteria, many people will simply warp the discussion until it
does. For example, I know something about the mecahanics of antennas,
something about using NEC models, and have a fair collection of
anecdotes and photos from my days in the 2way radio biz. However,
this thread is allegedly about antenna theory, where I am seriously
lacking. Since I don't want to twist the topic away from theory and
into reality, I haven't said anything worth reading (including this
rant).

On the contrary, I think it is quite a worthwile effort especially if
you summarize and publish the results for the benefit of all the arm
wavers saying things like "short antennas are poor radiators".

Good idea. I'm curious, but not curious enough to dig through several
hundred off topic comments to excavate relevent information.

Then you can discuss real data instead of arguing about what some naif
pulled out of his ass.

"Data is free. Information must be fought for"
(Former statistics instructor in college about 1968).

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html
It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

I also did a study of monopoles of various lengths above a ground.
There are a few that are less than 1/4 wave long which should help
with some short antenna phenomenon.
http://802.11junk.com/jeffl/antennas/Monopole/index.html
Length Gain
wl dBi
0.050 4.75
0.125 4.85
0.250 5.19
0.500 6.96
0.625 8.01
Notice that the gain doesn't really drop very much when the monopole
is shorter than 1/4 wavelength long. A 1/2 wave dipole exhibits a
similar lack of gain loss for short antennas. So, why are short
antennas generally frowned upon? Lots of reasons but the big one are
losses in the matching networks. the 0.050 wavelength antenna looks
like about 700 ohms impedance. The 0.125 antenna is about


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

Jeff Liebermann wrote:

snip

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html
It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

Yep, ground has a huge effect on some types of antennas.

An instructive slide show would be the vertical pattern of a horizontal
1/2 dipole at .1, .2, ... .5 wavelengths over ground.

Another one would be a 3 element beam at those heights.

I also did a study of monopoles of various lengths above a ground.
There are a few that are less than 1/4 wave long which should help
with some short antenna phenomenon.
http://802.11junk.com/jeffl/antennas/Monopole/index.html
Length Gain
wl dBi
0.050 4.75
0.125 4.85
0.250 5.19
0.500 6.96
0.625 8.01
Notice that the gain doesn't really drop very much when the monopole
is shorter than 1/4 wavelength long. A 1/2 wave dipole exhibits a
similar lack of gain loss for short antennas. So, why are short
antennas generally frowned upon? Lots of reasons but the big one are
losses in the matching networks. the 0.050 wavelength antenna looks
like about 700 ohms impedance. The 0.125 antenna is about

Nope, the vertical does the same thing when shortened from 1/4 as a
dipole shortened from 1/2 wave.



--
Jim Pennino

On 10/10/2014 3:08 PM, wrote:
John S wrote:
On 10/10/2014 1:50 PM, wrote:
John S wrote:
The thread about a new philosophy was about 246 posts long including the
drift into mechanisms of photons and quarks.

I wish to start this thread by discussing the merits of dipoles with
respect to length. I really don't want to start another thread of
flames. Please help me do this.

Let's confine the discussion to...

* It is a wire dipole (keep the wire AWG to practical values, please).
* The dipole's length is variable.
* It may or may not have wire resistance (state your value).
* The source is placed at the center of the antenna.
* There is no transmission line.
* There are no matching devices.
* This is a theoretical discussion but may include practical parameters.

EZNEC or NEC, provides answers to these questions, I think. I will do
some modeling and I'd like to compare my results to other results.

It does.

Let's kick them around.

There is nothing to kick around unless you want to argue about whether
the various NEC implementations provide valid results.

What NEC will tell you is that as the .5 wave dipole gets shorter and
shorter, the resistive part of the antenna impedance decreases and the
capacitive part increases and the patern and maximum gain changes very
slightly.

As the ratio of resistive input impedance to the wire resistance get
smaller, the I^2R losses increase.

But don't let that stop you from doing it.

People often learn much better from actual doing then they do from lectures.

BTW, you have to pay some attention to segmentation and as you get smaller
and smaller the segmentation limits just how accurate the simulation is.

Ok, I guess I had hoped to have a good conversation concerning the subject.

Jim has convinced me that it is not a worthwhile effort.

Cheers.


On the contrary, I think it is quite a worthwile effort especially if
you summarize and publish the results for the benefit of all the arm
wavers saying things like "short antennas are poor radiators".

Then you can discuss real data instead of arguing about what some naif
pulled out of his ass.