8405a working and measuring resonance?
 

I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are. Anyway, it
seems we have some agreement on the 600 nH value, although my physical NEC
helix models do not agree based on my estimate of your coil dimensions. I
understand that EZNec uses a "Minninec" ground, which allows antenna contact
with a perfect ground, but uses actual ground parameters to analyze the
reflections. I am not sure about this, but would assume from the point of
view of the input impedance, that the ground would be considered perfect;
and therefore lossless. I also noticed I had some borderline NEC warnings
when attempting to construct a coil with #10 AWG, so sometimes had to resort
to a much thinner conductor.

My models showed about 17 ohms at resonance when connected to a perfect
ground. The only time I observed impedances as low as 6 ohms was far from
resonance when the antenna was highly capacitive. Ideally I should
construct a ground screen, but for the time being will consider a perfect
ground.

A free space dipole might be easier to model, but I am curious to understand
why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured 600nH.
That is the value I used when I modeled this antenna using EZNec. It
showed resonance at about 145 MHz and 12 Ohms. (That was using an average
real ground.)

If I assume the antenna measurements are correct then is it the ground
that accounts for the difference between 6 Ohms and the modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It is a 4
inch base, 5 turns at 40 percent spacing on a .8 diameter inch form and a
4 inch tip. The material is Num 10 solid copper. I adjust the frequency
by stretching or compressing the coil. Currently it is resonant at about
141.7 Mhz. The 8405a shows a phase shift of 1 degree per 30 kc change in
frequency.

I have used both the vertload model and the EZNEC model. Both predict an
antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db power difference
between forward and reverse. The antenna shows a 10 db power difference
between forward and reverse.

Thanks - Dan


Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in length
from 0.8" to 1.6". The inductance values are 380 - 490 nH. An,
approximately 9" long monopole, with a 5 turn helix appears to be
resonant at about 190 MHz, with a highly reactive 6 ohm input impedance
at 141 MHz. Using a lumped element simulation the required load
inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard single
port network analyzer calibration and measure the actual input impedance
of the antenna.

Frank

8405a working and measuring resonance?
 

Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have any
experience with 4nec2, but have taken a quick look at the NEC manual to
figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length of
4". Since the GH card position is fixed it must be followed by a coordinate
transformation "GM" to position the helix, and the GW 1, card to the desired
position. For some reason the last field (ITS field) was filled with a
decimal number indicating the range of "Tags" to be moved (000.051 which
means all tags from zero to 51, but there are only 2 tags prior to the GM
card, so don't know why this happened). In any case this worked on my
model. The default entry for the ITS field is zero, or just leave blank.
This works fine for me, and just moves the GW 1, and GH card positions as
desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is only
when there are other geometry cards present that the GM function fails.

More study of the help menu in 4nec2 is required to figure out the correct
structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are. Anyway,
it seems we have some agreement on the 600 nH value, although my physical
NEC helix models do not agree based on my estimate of your coil
dimensions. I understand that EZNec uses a "Minninec" ground, which
allows antenna contact with a perfect ground, but uses actual ground
parameters to analyze the reflections. I am not sure about this, but
would assume from the point of view of the input impedance, that the
ground would be considered perfect; and therefore lossless. I also
noticed I had some borderline NEC warnings when attempting to construct a
coil with #10 AWG, so sometimes had to resort to a much thinner
conductor.

My models showed about 17 ohms at resonance when connected to a perfect
ground. The only time I observed impedances as low as 6 ohms was far
from resonance when the antenna was highly capacitive. Ideally I should
construct a ground screen, but for the time being will consider a perfect
ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using EZNec.
It showed resonance at about 145 MHz and 12 Ohms. (That was using an
average real ground.)

If I assume the antenna measurements are correct then is it the ground
that accounts for the difference between 6 Ohms and the modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It is a
4 inch base, 5 turns at 40 percent spacing on a .8 diameter inch form
and a 4 inch tip. The material is Num 10 solid copper. I adjust the
frequency by stretching or compressing the coil. Currently it is
resonant at about 141.7 Mhz. The 8405a shows a phase shift of 1 degree
per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both predict
an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db power
difference between forward and reverse. The antenna shows a 10 db power
difference between forward and reverse.

Thanks - Dan


Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in length
from 0.8" to 1.6". The inductance values are 380 - 490 nH. An,
approximately 9" long monopole, with a 5 turn helix appears to be
resonant at about 190 MHz, with a highly reactive 6 ohm input impedance
at 141 MHz. Using a lumped element simulation the required load
inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard single
port network analyzer calibration and measure the actual input impedance
of the antenna.

Frank

8405a working and measuring resonance?
 

Ok Dan, figured where the problem was. It is just necessary to set the ITS
field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...
Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have any
experience with 4nec2, but have taken a quick look at the NEC manual to
figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case this
worked on my model. The default entry for the ITS field is zero, or just
leave blank. This works fine for me, and just moves the GW 1, and GH card
positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the correct
structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are. Anyway,
it seems we have some agreement on the 600 nH value, although my
physical NEC helix models do not agree based on my estimate of your coil
dimensions. I understand that EZNec uses a "Minninec" ground, which
allows antenna contact with a perfect ground, but uses actual ground
parameters to analyze the reflections. I am not sure about this, but
would assume from the point of view of the input impedance, that the
ground would be considered perfect; and therefore lossless. I also
noticed I had some borderline NEC warnings when attempting to construct
a coil with #10 AWG, so sometimes had to resort to a much thinner
conductor.

My models showed about 17 ohms at resonance when connected to a perfect
ground. The only time I observed impedances as low as 6 ohms was far
from resonance when the antenna was highly capacitive. Ideally I should
construct a ground screen, but for the time being will consider a
perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using EZNec.
It showed resonance at about 145 MHz and 12 Ohms. (That was using an
average real ground.)

If I assume the antenna measurements are correct then is it the ground
that accounts for the difference between 6 Ohms and the modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It is
a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter inch
form and a 4 inch tip. The material is Num 10 solid copper. I adjust
the frequency by stretching or compressing the coil. Currently it is
resonant at about 141.7 Mhz. The 8405a shows a phase shift of 1 degree
per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both predict
an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db power
difference between forward and reverse. The antenna shows a 10 db
power difference between forward and reverse.

Thanks - Dan


Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH. An,
approximately 9" long monopole, with a 5 turn helix appears to be
resonant at about 190 MHz, with a highly reactive 6 ohm input impedance
at 141 MHz. Using a lumped element simulation the required load
inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard single
port network analyzer calibration and measure the actual input
impedance of the antenna.

Frank

8405a working and measuring resonance?
 

What are these "Cards" you guys are referring to ?

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the ITS
field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...
Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have any
experience with 4nec2, but have taken a quick look at the NEC manual to
figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case this
worked on my model. The default entry for the ITS field is zero, or just
leave blank. This works fine for me, and just moves the GW 1, and GH card
positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the correct
structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are. Anyway,
it seems we have some agreement on the 600 nH value, although my
physical NEC helix models do not agree based on my estimate of your coil
dimensions. I understand that EZNec uses a "Minninec" ground, which
allows antenna contact with a perfect ground, but uses actual ground
parameters to analyze the reflections. I am not sure about this, but
would assume from the point of view of the input impedance, that the
ground would be considered perfect; and therefore lossless. I also
noticed I had some borderline NEC warnings when attempting to construct
a coil with #10 AWG, so sometimes had to resort to a much thinner
conductor.

My models showed about 17 ohms at resonance when connected to a perfect
ground. The only time I observed impedances as low as 6 ohms was far
from resonance when the antenna was highly capacitive. Ideally I should
construct a ground screen, but for the time being will consider a
perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using EZNec.
It showed resonance at about 145 MHz and 12 Ohms. (That was using an
average real ground.)

If I assume the antenna measurements are correct then is it the ground
that accounts for the difference between 6 Ohms and the modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It is
a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter inch
form and a 4 inch tip. The material is Num 10 solid copper. I adjust
the frequency by stretching or compressing the coil. Currently it is
resonant at about 141.7 Mhz. The 8405a shows a phase shift of 1 degree
per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both predict
an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db power
difference between forward and reverse. The antenna shows a 10 db
power difference between forward and reverse.

Thanks - Dan

Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH. An,
approximately 9" long monopole, with a 5 turn helix appears to be
resonant at about 190 MHz, with a highly reactive 6 ohm input impedance
at 141 MHz. Using a lumped element simulation the required load
inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard single
port network analyzer calibration and measure the actual input
impedance of the antenna.

Frank

8405a working and measuring resonance?
 

A card is a line of NEC code. I guess it is a hold over from the old days
when NEC must have been run with FORTRAN punch-cards on a mainframe
computer.

Frank

"David" wrote in message
...
What are these "Cards" you guys are referring to ?

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the
ITS field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...
Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have
any experience with 4nec2, but have taken a quick look at the NEC manual
to figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case
this worked on my model. The default entry for the ITS field is zero,
or just leave blank. This works fine for me, and just moves the GW 1,
and GH card positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the
correct structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are.
Anyway, it seems we have some agreement on the 600 nH value, although
my physical NEC helix models do not agree based on my estimate of your
coil dimensions. I understand that EZNec uses a "Minninec" ground,
which allows antenna contact with a perfect ground, but uses actual
ground parameters to analyze the reflections. I am not sure about
this, but would assume from the point of view of the input impedance,
that the ground would be considered perfect; and therefore lossless.
I also noticed I had some borderline NEC warnings when attempting to
construct a coil with #10 AWG, so sometimes had to resort to a much
thinner conductor.

My models showed about 17 ohms at resonance when connected to a
perfect ground. The only time I observed impedances as low as 6 ohms
was far from resonance when the antenna was highly capacitive.
Ideally I should construct a ground screen, but for the time being
will consider a perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using
EZNec. It showed resonance at about 145 MHz and 12 Ohms. (That was
using an average real ground.)

If I assume the antenna measurements are correct then is it the
ground that accounts for the difference between 6 Ohms and the
modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It
is a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter
inch form and a 4 inch tip. The material is Num 10 solid copper. I
adjust the frequency by stretching or compressing the coil.
Currently it is resonant at about 141.7 Mhz. The 8405a shows a
phase shift of 1 degree per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both
predict an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db
power difference between forward and reverse. The antenna shows a
10 db power difference between forward and reverse.

Thanks - Dan

Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH.
An, approximately 9" long monopole, with a 5 turn helix appears to
be resonant at about 190 MHz, with a highly reactive 6 ohm input
impedance at 141 MHz. Using a lumped element simulation the required
load inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard
single port network analyzer calibration and measure the actual
input impedance of the antenna.

Frank

8405a working and measuring resonance?
 

Frank,

Thanks for that.

BTW: Does anyone know where I can get the wgnuplot.exe for 4nec2ex ?
The site has a link to the gnuplot only, I tried this link but is brings
up a page error.

Frank wrote:
A card is a line of NEC code. I guess it is a hold over from the old days
when NEC must have been run with FORTRAN punch-cards on a mainframe
computer.

Frank

"David" wrote in message
...
What are these "Cards" you guys are referring to ?

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the
ITS field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...
Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have
any experience with 4nec2, but have taken a quick look at the NEC manual
to figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case
this worked on my model. The default entry for the ITS field is zero,
or just leave blank. This works fine for me, and just moves the GW 1,
and GH card positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the
correct structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are.
Anyway, it seems we have some agreement on the 600 nH value, although
my physical NEC helix models do not agree based on my estimate of your
coil dimensions. I understand that EZNec uses a "Minninec" ground,
which allows antenna contact with a perfect ground, but uses actual
ground parameters to analyze the reflections. I am not sure about
this, but would assume from the point of view of the input impedance,
that the ground would be considered perfect; and therefore lossless.
I also noticed I had some borderline NEC warnings when attempting to
construct a coil with #10 AWG, so sometimes had to resort to a much
thinner conductor.

My models showed about 17 ohms at resonance when connected to a
perfect ground. The only time I observed impedances as low as 6 ohms
was far from resonance when the antenna was highly capacitive.
Ideally I should construct a ground screen, but for the time being
will consider a perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using
EZNec. It showed resonance at about 145 MHz and 12 Ohms. (That was
using an average real ground.)

If I assume the antenna measurements are correct then is it the
ground that accounts for the difference between 6 Ohms and the
modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It
is a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter
inch form and a 4 inch tip. The material is Num 10 solid copper. I
adjust the frequency by stretching or compressing the coil.
Currently it is resonant at about 141.7 Mhz. The 8405a shows a
phase shift of 1 degree per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both
predict an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db
power difference between forward and reverse. The antenna shows a
10 db power difference between forward and reverse.

Thanks - Dan
Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH.
An, approximately 9" long monopole, with a 5 turn helix appears to
be resonant at about 190 MHz, with a highly reactive 6 ohm input
impedance at 141 MHz. Using a lumped element simulation the required
load inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard
single port network analyzer calibration and measure the actual
input impedance of the antenna.

Frank

8405a working and measuring resonance?
 

Frank,

Umm. I tried to set the GM ITS field to 0 and that did not make any difference.
Can you forward the nec file that does not produce the error?

Thanks - Dan

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the ITS
field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...

Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have any
experience with 4nec2, but have taken a quick look at the NEC manual to
figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case this
worked on my model. The default entry for the ITS field is zero, or just
leave blank. This works fine for me, and just moves the GW 1, and GH card
positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the correct
structure for the ITS field.

Frank


"dansawyeror" wrote in message
...

I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:

Dan,

Be interested to see what the exact dimensions of the coil are. Anyway,
it seems we have some agreement on the 600 nH value, although my
physical NEC helix models do not agree based on my estimate of your coil
dimensions. I understand that EZNec uses a "Minninec" ground, which
allows antenna contact with a perfect ground, but uses actual ground
parameters to analyze the reflections. I am not sure about this, but
would assume from the point of view of the input impedance, that the
ground would be considered perfect; and therefore lossless. I also
noticed I had some borderline NEC warnings when attempting to construct
a coil with #10 AWG, so sometimes had to resort to a much thinner
conductor.

My models showed about 17 ohms at resonance when connected to a perfect
ground. The only time I observed impedances as low as 6 ohms was far
from resonance when the antenna was highly capacitive. Ideally I should
construct a ground screen, but for the time being will consider a
perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...


Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using EZNec.
It showed resonance at about 145 MHz and 12 Ohms. (That was using an
average real ground.)

If I assume the antenna measurements are correct then is it the ground
that accounts for the difference between 6 Ohms and the modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:


"dansawyeror" wrote in message
...



Frank,

The antenna I am trying to model is a center 'loaded vertical'. It is
a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter inch
form and a 4 inch tip. The material is Num 10 solid copper. I adjust
the frequency by stretching or compressing the coil. Currently it is
resonant at about 141.7 Mhz. The 8405a shows a phase shift of 1 degree
per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both predict
an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db power
difference between forward and reverse. The antenna shows a 10 db
power difference between forward and reverse.

Thanks - Dan


Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH. An,
approximately 9" long monopole, with a 5 turn helix appears to be
resonant at about 190 MHz, with a highly reactive 6 ohm input impedance
at 141 MHz. Using a lumped element simulation the required load
inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard single
port network analyzer calibration and measure the actual input
impedance of the antenna.

Frank

8405a working and measuring resonance?
 

Dan, here is the code I copied and pasted it directly from 4nec2 nec edit
page. I have not yet figured out how to have swept frequency data, as the
program only seems to recognize the first frequency of 135 MHz.

Frank

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 0
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN


"dansawyeror" wrote in message
...
Frank,

Umm. I tried to set the GM ITS field to 0 and that did not make any
difference. Can you forward the nec file that does not produce the error?

Thanks - Dan

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the
ITS field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...

Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have any
experience with 4nec2, but have taken a quick look at the NEC manual to
figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case this
worked on my model. The default entry for the ITS field is zero, or just
leave blank. This works fine for me, and just moves the GW 1, and GH card
positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the
correct structure for the ITS field.

Frank


"dansawyeror" wrote in message
...

I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:

Dan,

Be interested to see what the exact dimensions of the coil are.
Anyway, it seems we have some agreement on the 600 nH value, although
my physical NEC helix models do not agree based on my estimate of your
coil dimensions. I understand that EZNec uses a "Minninec" ground,
which allows antenna contact with a perfect ground, but uses actual
ground parameters to analyze the reflections. I am not sure about
this, but would assume from the point of view of the input impedance,
that the ground would be considered perfect; and therefore lossless. I
also noticed I had some borderline NEC warnings when attempting to
construct a coil with #10 AWG, so sometimes had to resort to a much
thinner conductor.

My models showed about 17 ohms at resonance when connected to a perfect
ground. The only time I observed impedances as low as 6 ohms was far
from resonance when the antenna was highly capacitive. Ideally I
should construct a ground screen, but for the time being will consider
a perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...


Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using
EZNec. It showed resonance at about 145 MHz and 12 Ohms. (That was
using an average real ground.)

If I assume the antenna measurements are correct then is it the ground
that accounts for the difference between 6 Ohms and the modeled 12
Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:


"dansawyeror" wrote in message
...



Frank,

The antenna I am trying to model is a center 'loaded vertical'. It
is a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter
inch form and a 4 inch tip. The material is Num 10 solid copper. I
adjust the frequency by stretching or compressing the coil.
Currently it is resonant at about 141.7 Mhz. The 8405a shows a phase
shift of 1 degree per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both
predict an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db
power difference between forward and reverse. The antenna shows a 10
db power difference between forward and reverse.

Thanks - Dan


Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH.
An, approximately 9" long monopole, with a 5 turn helix appears to be
resonant at about 190 MHz, with a highly reactive 6 ohm input
impedance at 141 MHz. Using a lumped element simulation the required
load inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard
single port network analyzer calibration and measure the actual input
impedance of the antenna.

Frank

8405a working and measuring resonance?
 

"David" wrote in message
...
Frank,

Thanks for that.

BTW: Does anyone know where I can get the wgnuplot.exe for 4nec2ex ?
The site has a link to the gnuplot only, I tried this link but is brings
up a page error.

Dave, sorry I am not very familiar with 4nec, so have no idea what
wgnuplot.exe is. Most of my NEC experience is with NEC-Win Pro, which is so
straightforward and easy to use. Not that I mean to degrade 4nec2, I think
the guys have done a great job for the free software. I guess your best
approach is to keep bugging Arie as I am sure he knows.

Frank


Frank wrote:
A card is a line of NEC code. I guess it is a hold over from the old
days when NEC must have been run with FORTRAN punch-cards on a mainframe
computer.

Frank

"David" wrote in message
...
What are these "Cards" you guys are referring to ?

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the
ITS field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...
Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have
any experience with 4nec2, but have taken a quick look at the NEC
manual to figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0.
My first "GW" card positions a wire from the top of the helix with a
length of 4". Since the GH card position is fixed it must be followed
by a coordinate transformation "GM" to position the helix, and the GW
1, card to the desired position. For some reason the last field (ITS
field) was filled with a decimal number indicating the range of "Tags"
to be moved (000.051 which means all tags from zero to 51, but there
are only 2 tags prior to the GM card, so don't know why this
happened). In any case this worked on my model. The default entry
for the ITS field is zero, or just leave blank. This works fine for
me, and just moves the GW 1, and GH card positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the
correct structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are.
Anyway, it seems we have some agreement on the 600 nH value,
although my physical NEC helix models do not agree based on my
estimate of your coil dimensions. I understand that EZNec uses a
"Minninec" ground, which allows antenna contact with a perfect
ground, but uses actual ground parameters to analyze the
reflections. I am not sure about this, but would assume from the
point of view of the input impedance, that the ground would be
considered perfect; and therefore lossless. I also noticed I had
some borderline NEC warnings when attempting to construct a coil
with #10 AWG, so sometimes had to resort to a much thinner
conductor.

My models showed about 17 ohms at resonance when connected to a
perfect ground. The only time I observed impedances as low as 6
ohms was far from resonance when the antenna was highly capacitive.
Ideally I should construct a ground screen, but for the time being
will consider a perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using
EZNec. It showed resonance at about 145 MHz and 12 Ohms. (That was
using an average real ground.)

If I assume the antenna measurements are correct then is it the
ground that accounts for the difference between 6 Ohms and the
modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'.
It is a 4 inch base, 5 turns at 40 percent spacing on a .8
diameter inch form and a 4 inch tip. The material is Num 10 solid
copper. I adjust the frequency by stretching or compressing the
coil. Currently it is resonant at about 141.7 Mhz. The 8405a
shows a phase shift of 1 degree per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both
predict an antenna R of about 5 Ohms. The 25 Ohm load shows a 12
db power difference between forward and reverse. The antenna
shows a 10 db power difference between forward and reverse.

Thanks - Dan
Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH.
An, approximately 9" long monopole, with a 5 turn helix appears to
be resonant at about 190 MHz, with a highly reactive 6 ohm input
impedance at 141 MHz. Using a lumped element simulation the
required load inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard
single port network analyzer calibration and measure the actual
input impedance of the antenna.

Frank

8405a working and measuring resonance?
 

On Fri, 27 Jan 2006 23:29:38 GMT, David
wrote:

Frank,

Thanks for that.

BTW: Does anyone know where I can get the wgnuplot.exe for 4nec2ex ?
The site has a link to the gnuplot only, I tried this link but is brings
up a page error.

I didn't find it too hard, I followed the links from Arie's page.

Try ftp://ftp.gnuplot.info/pub/gnuplot/ and see if you can identify
the correct binary for your (unstated) needs (presumably one of the
windows versions, probably win32 since you wanted w*.exe).

Owen

Frank wrote:
A card is a line of NEC code. I guess it is a hold over from the old days
when NEC must have been run with FORTRAN punch-cards on a mainframe
computer.

Frank

"David" wrote in message
...
What are these "Cards" you guys are referring to ?

Frank wrote:
Ok Dan, figured where the problem was. It is just necessary to set the
ITS field to zero, and the code runs ok.

Frank

"Frank" wrote in message
news:eXpCf.199081$OU5.8916@clgrps13...
Dan, I am running NEC-Win Pro from Nittany Scientific. I do not have
any experience with 4nec2, but have taken a quick look at the NEC manual
to figure out what the error is.
The "GH" card generates a helix with the base positioned at z = 0. My
first "GW" card positions a wire from the top of the helix with a length
of 4". Since the GH card position is fixed it must be followed by a
coordinate transformation "GM" to position the helix, and the GW 1, card
to the desired position. For some reason the last field (ITS field) was
filled with a decimal number indicating the range of "Tags" to be moved
(000.051 which means all tags from zero to 51, but there are only 2 tags
prior to the GM card, so don't know why this happened). In any case
this worked on my model. The default entry for the ITS field is zero,
or just leave blank. This works fine for me, and just moves the GW 1,
and GH card positions as desired.

Experimenting with 4nec2 indicates if the only geometry card is a GH,
followed by a GM card, then the transformation appears to work. It is
only when there are other geometry cards present that the GM function
fails.

More study of the help menu in 4nec2 is required to figure out the
correct structure for the ITS field.

Frank


"dansawyeror" wrote in message
...
I tried to run the nec in 4nec2. It produces and error"

"ITS GM card (x,y) not supported in nec2 engine"

Which model are you using? Do you know the source of this error?

Thanks - Dan




Frank wrote:
Dan,

Be interested to see what the exact dimensions of the coil are.
Anyway, it seems we have some agreement on the 600 nH value, although
my physical NEC helix models do not agree based on my estimate of your
coil dimensions. I understand that EZNec uses a "Minninec" ground,
which allows antenna contact with a perfect ground, but uses actual
ground parameters to analyze the reflections. I am not sure about
this, but would assume from the point of view of the input impedance,
that the ground would be considered perfect; and therefore lossless.
I also noticed I had some borderline NEC warnings when attempting to
construct a coil with #10 AWG, so sometimes had to resort to a much
thinner conductor.

My models showed about 17 ohms at resonance when connected to a
perfect ground. The only time I observed impedances as low as 6 ohms
was far from resonance when the antenna was highly capacitive.
Ideally I should construct a ground screen, but for the time being
will consider a perfect ground.

A free space dipole might be easier to model, but I am curious to
understand why there are discrepancies in the monopole modeling.

Frank

PS, be interested in any comments on my NEC code:

CM Loaded 2 m monopole
CE
GW 1 15 0.4 0 5.6 0.4 0 1.6 0.025
GH 2 50 .32 1.6 .4 .4 .4 .4 0.025
GM 100 0 0 0 0 0 0 4 000.051
GW 3 15 0.4 0 4 0.4 0 0 0.025
GS 0 0 0.025400
GE 1
GN 1
EX 0 3 15 00 1 0
LD 5 101 1 15 5.8001E7
LD 5 102 1 50 5.8001E7
LD 5 3 1 15 5.8001E7
FR 0 41 0 0 135 2
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN
"dansawyeror" wrote in message
...

Frank,

I will re-measure the coil dimensions. The recall the coil measured
600nH. That is the value I used when I modeled this antenna using
EZNec. It showed resonance at about 145 MHz and 12 Ohms. (That was
using an average real ground.)

If I assume the antenna measurements are correct then is it the
ground that accounts for the difference between 6 Ohms and the
modeled 12 Ohms?

Now I am on to model and measure a center loaded dipole.

Dan

Frank wrote:

"dansawyeror" wrote in message
...


Frank,

The antenna I am trying to model is a center 'loaded vertical'. It
is a 4 inch base, 5 turns at 40 percent spacing on a .8 diameter
inch form and a 4 inch tip. The material is Num 10 solid copper. I
adjust the frequency by stretching or compressing the coil.
Currently it is resonant at about 141.7 Mhz. The 8405a shows a
phase shift of 1 degree per 30 kc change in frequency.

I have used both the vertload model and the EZNEC model. Both
predict an antenna R of about 5 Ohms. The 25 Ohm load shows a 12 db
power difference between forward and reverse. The antenna shows a
10 db power difference between forward and reverse.

Thanks - Dan
Dan, I have modelled a 5 turn inductor, 0.8" diameter, varying in
length from 0.8" to 1.6". The inductance values are 380 - 490 nH.
An, approximately 9" long monopole, with a 5 turn helix appears to
be resonant at about 190 MHz, with a highly reactive 6 ohm input
impedance at 141 MHz. Using a lumped element simulation the required
load inductance, for 141 MHz, is about 600 nH.

The only way to resolve these discrepancies is to do a standard
single port network analyzer calibration and measure the actual
input impedance of the antenna.

Frank

--