Hi, Billy, thanks so much for your offer.
I worked on it some more, using some suggestions from another respondent
that wrote to me privately. It seemed that the main change came from
changing the Transmission Line (TL) card. The NEC2 definition of the TL
card said that if the length of the transmission line was left blank, it
would use the distance from the two attachment point. xnec2c wouldn't
let me leave it just blank, so I mistakenly thought that zero would be
the same a blank. Putting in the real distance, plus some other changes
to the values for real and imaginary parts of the ends, gave me a
working model. I've pasted in my model, and attached it, if anyone wants
to take a look.
By experimenting with the model, I also learned that I could separate
the dipoles by as little as 1mm and still get a valid result.
I hope I'm not demanding, but if anyone wants to take a shot at my other
questions, I welcome any advice or suggestions:
2. sweeping more than one frequency range?
3. producing 2D azimuth and elevation charts?
4. eliminate any unneeded cards?
5. further suggestions for improvement of this model.
Thanks, again, for all your help and advice.
-Kevin
KC3KZ
New, working model:
=========================================
CM --- NEC2 Input File created or edited by xnec2c 3.6.1-beta ---
CM 40/20M fan dipole, 10m elevation over 'normal' ground.
CM Dipoles connected by short transmission lines.
CM Used wire diameter of #12, 2mm dia, 1mm radius, instead of 0.3mm. No
change.
CM Changed TL. Entered length, changed all R and I to 0. Gave response
of dip below SWR 2:1 at 7 and 14MHz.
CM Kevin Zembower, KC3KZ
CE --- End Comments ---
GW 1 41 0.00000E+00 -1.01170E+01 1.00000E+01 0.00000E+00
1.01170E+01 1.00000E+01 1.00000E-03
GW 2 21 0.00000E+00 -5.19250E+00 9.99900E+00 0.00000E+00
5.19250E+00 9.99900E+00 1.00000E-03
GE -1 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
EX 0 2 11 0 1.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
TL 1 21 2 11 5.00000E+01 1.00000E-03 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
FR 0 501 0 0 6.00000E+00 1.80000E-02 1.50000E+01
0.00000E+00 0.00000E+00 0.00000E+00
NH 1 1 1 1 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
NE 1 1 1 1 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
RP 0 9 37 1000 0.00000E+00 0.00000E+00 1.00000E+01
1.00000E+01 0.00000E+00 0.00000E+00
GN 2 0 0 0 1.20000E+01 1.00000E-02 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
EN 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
=========================================
On 7/23/20 4:47 AM, Billy Cox wrote:
Hi Kevin,
I will take a look at this when I am back home
and at the PC with my modeling software.
I do not have the same software as you are using,
but will see if I can import your file. The end
results of the model should be the same.
In the meanwhile, try modeling this as two antennas,
using the same dimensions, and see what the SWR is as
to a more reasonable value for each individual band.
73 until the weekend.
Billy, AA4NU
On 07/22/2020 11:07 AM Kevin Zembower via Antennaware
<antennaware@contesting.com> wrote:
Hello, this is my first post on this list. The folks on TowerTalk
suggested I ask my modeling questions here.
I'm using xnec2c on a Ubuntu Linux desktop to perform the modeling. Is
anyone here also using this software?
I'm trying to model a 40/20M dipole. My two dipoles are connected by a 6
inch (0.1524m) transmission line. When I use the deck below, I don't get
an error, but do produce a VSWR of 999 on all the swept frequencies from
7-14.35MHz.
I have these questions:
1. What am I doing wrong in this model?
2. Using either the xnec2c interface, or the nec2c engine, is it
possible to sweep more than one frequency range? I'm only interested in
7-7.3MHz and 14-14.35MHz, and don't care about the frequencies between
the bands.
3. Can xnec2c, or the nec2c engine, produce 2D azimuth and elevation
charts? The 3D illustrations that xnec2c produces are pretty, but hard
to read.
4. Can I eliminate any of the cards in this deck? My starting point was
the deck of cards that xnec2c produces when you ask for a new file. Are
all of these needed?
5. Do you all have any suggestions for me to improve this model? Is
there anything I'm overlooking. As I said, this is my first time trying
to model an antenna, and the details can overwhelm me.
Thanks so much for your suggestions and advice. I look forward to
hearing from you.
-Kevin
KC3KZ
(Deck also attached, to prevent email formatting errors)
CM --- NEC2 Input File created or edited by xnec2c 3.6.1-beta ---
CM 40/20M fan dipole, 10m elevation over 'normal' ground.
CM Dipoles connected by short transmission lines.
CM Used wire diameter of #28 AWG, 0.0126in, 0.00016002m radius
CM Kevin Zembower, KC3KZ
CE --- End Comments ---
GW 1 41 0.00000E+00 -1.01370E+01 1.00000E+01 0.00000E+00
1.01370E+01 1.00000E+01 1.50000E-04
GW 2 21 0.00000E+00 -5.28700E+00 9.84800E+00 0.00000E+00
5.28700E+00 9.84800E+00 1.50000E-04
GE -1 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
EX 0 2 11 0 1.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
TL 1 21 2 11 2.00000E-02 0.00000E+00 2.00000E-02
0.00000E+00 5.00000E+01 0.00000E+00
FR 0 51 0 0 7.00000E+00 1.47000E-01 1.43500E+01
0.00000E+00 0.00000E+00 0.00000E+00
NH 1 1 1 1 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
NE 1 1 1 1 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
RP 0 9 37 1000 0.00000E+00 0.00000E+00 1.00000E+01
1.00000E+01 0.00000E+00 0.00000E+00
GN 2 0 0 0 1.20000E+01 1.00000E-02 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
EN 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00
0.00000E+00 0.00000E+00 0.00000E+00
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40_20mDipole_10mElev_TransLine_rev2_KC3KZ.nec
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