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.

Apologies for the blank post. I hit the wrong button.

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?



--
Jim Pennino

On 10/11/2014 12:51 PM, wrote:
John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?


0.05 #8 0.515 -.41 1.36 91.1%


Free space, no ground loss.

John S wrote:
On 10/11/2014 12:51 PM, wrote:
John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?


0.05 #8 0.515 -.41 1.36 91.1%


Free space, no ground loss.

So it seems that a .05 lamda dipole is only about 7% less efficient than
a full size dipole wit suitable wire...

So much for "short antennas are not efficient".

Now, if we could just invent room temperature superconductor wire and
lossles toroids we could match the thing to a 50 Ohm system...


--
Jim Pennino

On 10/12/2014 1:21 PM, wrote:
John S wrote:
On 10/11/2014 12:51 PM, wrote:
John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?


0.05 #8 0.515 -.41 1.36 91.1%


Free space, no ground loss.

So it seems that a .05 lamda dipole is only about 7% less efficient than
a full size dipole wit suitable wire...

So much for "short antennas are not efficient".

(snip extraneous input)


Yes, Jim, that is so. In fact, that was the hidden reason for the
exercise. I was hoping this would provide an example to let others know
that it is not the antenna length that is the problem as Gareth
proposed. I was hoping that others would take the investigation into
their own hands as a result.

I noted that you tried to foul me up with the unreasonable wire size.
EZNEC has a nice warning feature to take care of it.

John S wrote:
On 10/12/2014 1:21 PM, wrote:
John S wrote:
On 10/11/2014 12:51 PM, wrote:
John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?


0.05 #8 0.515 -.41 1.36 91.1%


Free space, no ground loss.

So it seems that a .05 lamda dipole is only about 7% less efficient than
a full size dipole wit suitable wire...

So much for "short antennas are not efficient".

(snip extraneous input)


Yes, Jim, that is so. In fact, that was the hidden reason for the
exercise. I was hoping this would provide an example to let others know
that it is not the antenna length that is the problem as Gareth
proposed. I was hoping that others would take the investigation into
their own hands as a result.

I noted that you tried to foul me up with the unreasonable wire size.
EZNEC has a nice warning feature to take care of it.

What "unreasonable wire size"? #8 wire is readily available and often
used to make antenna elements, as is 1/8 th aluminum, which is only a
few thousands of an inch different.

Or are you refering to issues with segmentation and fat, short wires which I
thought I had warned you about?


--
Jim Pennino

On 10/12/2014 2:14 PM, wrote:
John S wrote:
On 10/12/2014 1:21 PM, wrote:
John S wrote:
On 10/11/2014 12:51 PM, wrote:
John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?


0.05 #8 0.515 -.41 1.36 91.1%


Free space, no ground loss.

So it seems that a .05 lamda dipole is only about 7% less efficient than
a full size dipole wit suitable wire...

So much for "short antennas are not efficient".

(snip extraneous input)


Yes, Jim, that is so. In fact, that was the hidden reason for the
exercise. I was hoping this would provide an example to let others know
that it is not the antenna length that is the problem as Gareth
proposed. I was hoping that others would take the investigation into
their own hands as a result.

I noted that you tried to foul me up with the unreasonable wire size.
EZNEC has a nice warning feature to take care of it.

What "unreasonable wire size"? #8 wire is readily available and often
used to make antenna elements, as is 1/8 th aluminum, which is only a
few thousands of an inch different.

Or are you refering to issues with segmentation and fat, short wires which I
thought I had warned you about?

Ok, wrong choice of words on my part. Sorry. Yes, I kinda thought you
were really testing me to see if I paid attention about the warning.

On Sat, 11 Oct 2014 11:47:22 -0500, John S
wrote:

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

Sounds about right except that it doesn't include any losses
introduced by the necessary matching network and real ground losses at
HF frequencies. Expanding my table to include radiation efficiency:

http://802.11junk.com/jeffl/antennas/Monopole/index.html
Length Gain Radiation
wl dBi Efficiency
0.050 4.75 99.09%
0.125 4.85 99.66%
0.250 5.19 99.93%
0.500 6.96 99.97%
0.625 8.01 99.93%
In other words, there's nothing inherent in the length of the radiator
that would affect radiation efficiency. If there is a drop in
radiation efficiency, then it's mostly due to ground losses, material
losses I2R, and matching losses).

I invite discussion in any case.

NEC: Power Efficiency vs. Radiation Efficiency
L. B. Cebik, W4RNL
http://www.antennex.com/w4rnl/col0504/amod75.html
Lots of examples of how "efficiency" calculations work, and how
various common antenna configurations affect the results. (I need to
re-read the article as there's plenty about this which I don't
understand very well). Test cases 5 and 6 are short monopoles, which
should have something to do with short dipoles. From the bottom of
the page:
"Unlike the vertical monopole, the horizontal dipole shows much
more regular changes of radiation efficiency with changes of
soil type, ranging from 80.01% over very good soil to 65.93%
over very poor soil."

--
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:
On Sat, 11 Oct 2014 11:47:22 -0500, John S
wrote:

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

Sounds about right except that it doesn't include any losses
introduced by the necessary matching network and real ground losses at
HF frequencies. Expanding my table to include radiation efficiency:

There is no feed because it is the ANTENNA that is being analyzed, not
an antenna SYSTEM.

And while I don't know if the simulation included it, NEC can include
the ground losses for the ANTENNA.

http://802.11junk.com/jeffl/antennas/Monopole/index.html
Length Gain Radiation
wl dBi Efficiency
0.050 4.75 99.09%
0.125 4.85 99.66%
0.250 5.19 99.93%
0.500 6.96 99.97%
0.625 8.01 99.93%
In other words, there's nothing inherent in the length of the radiator
that would affect radiation efficiency. If there is a drop in
radiation efficiency, then it's mostly due to ground losses, material
losses I2R, and matching losses).

Ground and I^2R losses of the antenna are shown by NEC.

Matching losses are NOT part of the antenna.

I invite discussion in any case.

NEC: Power Efficiency vs. Radiation Efficiency
L. B. Cebik, W4RNL
http://www.antennex.com/w4rnl/col0504/amod75.html
Lots of examples of how "efficiency" calculations work, and how
various common antenna configurations affect the results. (I need to
re-read the article as there's plenty about this which I don't
understand very well). Test cases 5 and 6 are short monopoles, which
should have something to do with short dipoles. From the bottom of
the page:
"Unlike the vertical monopole, the horizontal dipole shows much
more regular changes of radiation efficiency with changes of
soil type, ranging from 80.01% over very good soil to 65.93%
over very poor soil."

Yep, and once the issue of size versus efficieny is put to rest, it would
not be a bad idea to look at the real effects of ground, both in terms
of height in wavelengths and soil quality.



--
Jim Pennino

wrote in :

Yep, and once the issue of size versus efficieny is put to rest, it would
not be a bad idea to look at the real effects of ground, both in terms
of height in wavelengths and soil quality.


Thankyou. This is the bit I am most weak on (though I did not grasp all the
previous detail, the ground loss was an issue not lost on me, and is the
one I need most to solve in my next efforts). What is this NEC program, and
where can I find it? Sorry, but I have to ask, or Google will likely flood me
with Nippon Electric Company details.