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I forgot to mention, in that last set of commits, I added an option to specify a -R sweep,
which will sweep the new UHF Repack band here. Thought it might be handy.

Code:
[B]  -R, --rep, --uhf-37   adds a uhf (ch. 14-36) sweep[/B]
  -u, --uhf, --uhf-52   adds a uhf (ch. 14-51) sweep
  -U, --uhf-69          adds a uhf (ch. 14-69) sweep
  -V, --vhf-hi          adds a vhf-hi (ch. 7-13) sweep
  -v, --vhf-lo          adds a vhf-lo (ch. 1-6) sweep
 

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New necopt version and repo

I published new version 0.17.6aa0adc of the nec.opt scripts.

It contains the changes from majortom, plus some improvements for linux engines.
The sources have been on github for some time now, but I never published the link before.

If any body is interested in contributing please use the repo https://github.com/nikiml/nec.opt
 

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Thanks Nikiml, I will check it out.
I didn't realize u had been working on support for nec2c and nec2++.
I will try and play around with them engines sometime.
Thanks for letting us know where the repo lives, I will use your github repo from now on.
 

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Trying to learn how to use 4nec2 and are having trouble running a couple of holl_and designs.
CM UHF Super-2-Bay, VARIABLE Solid Triangles, 11 Reflector Rods, 4nec2 by holl_ands, 4Mar2015.
CM H+U 2-Bay WALLTENNA-PLUS with Extensions, In Rect. Loop, NO Refl, 4nec2 by holl_ands, 2Feb2015.
I download then remove word processor junk and most of the models work except the two above.
They come up with a INCORRECT LABEL FOR A COMMENT CARD error.
I noticed there was a CE mnemonic/ full stop missing in the CM line but didn't fix it.
Please help
 

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Here is the link
It's the first antenna with solid bowtie's.
Thanks
 

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I assume the problem u ran in to may have been related to the text editor in use on your end, from using a native windows editor, such as notepad or wordpad? If so, those are just awful.

If you haven't already try installing a "real text editor", such as Notepad++.

I copied the text from holl_ands' word document in to the native text editor in linux (vim), and it seems fine to me.
Ran straight away with no errors with nikiml's eval scripts and 4nec2.
here's a pastebin, look for the raw paste data near the bottom, and copy/paste that.
 

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Thanks majortom copy and pasted your raw file to notepad and it works.
I have been using Notepad but couldn't download from holl_and site.
Could i add a Rectangular Loop Resonator to this antenna to improve Hi VHF gain and SWR.
I'm trying to build a compact Hi VHF UHF wide freq band antenna for my caravan.
I need the wide freq bandwidth to receive TV while travelling around Australia
A reflector for more gain and narrow radiation pattern is not a problem as all tv stations Tx from one site per district.
It has to be small enough to store in the caravan yet receive Hi VHF.
That why I'm looking at a bowtie with rectangular Loop Resonator antenna single or 2 bay with reflector
Even if i use a single bay bowtie i assume the Rectangular Loop Resonator will still have to be the same size
Even if it's low gain as i have a 20db UHF/VHF low noise amplifier.
Could you suggest any antenna design
 

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I think I may have mentioned this before. Try to keep your system as simple as possible for the initial go around, until proven otherwise with testing that you actually need something more...
Around here, many people can get away with something as simple as this for adding VHF Hi to an existing UHF Antenna. This kit comes with a built in UHF/VHF Diplexer, can be clipped on to a fairly stout reflector screen but does come with some UV black Tie Wraps also, just in case ya have to tie down to a mast, etc.

Their kit is quite convenient, but you could easily make your own and come up with your own VHF/UHF Diplexer (UVSJ), add a couple short jumper cables and ur done.
Start with something simple like that and see how that flies.
 

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Been trying to use 4nec2 to model ultra wide bandwidth sheet metal bow ties.

They are supposed to have extremely good swr & flatter impedence.

Seems to be very hit & miss on the bow tie mesh.

Plus 4nec2 gives me a ton of warnings on sharp angles, and having problems with
segmentation.

Need to confirm the extremely good swr & flatter impedence of these sheet metal bow ties.

Is there any other good gui antenna modeling software, free or trial or demo, that
can do sheet metal bow ties?

Maybe using FDTD, or other method to model the rounded bow ties.
 

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Need to confirm the extremely good swr & flatter impedence of these sheet metal bow ties.
Bowties aren't supposed to have good SWR, they are supposed to have extremely wide band (possibly infinite) if SWR<2 constraint is OK.

basically, bowtie is dipole. (with small flare angle it is classical dipole).
when it's length is proportional to lambda/2 - it is half-wave Herzian dipole. It has low-impedance (73 Ohm for thin wire) and sharp resonance (steep jX curve)
when it's length is proportional to lambda - it is full-wave dipole. It has high-impedance (300....1000) and sharp resonance (steep jX curve)

in between - jX reactance goes negative, real part deviate between low resonance (~70 Ohm) to high resonance (~300-1000 Ohm)

It has infinite matching limited bandwidth, but not practical radiation pattern after length reach 1.5-lambda. RP distorts and is not usable for most applications (except massive phased array, where RP of individual element has no influence on phased array beam)

There is no free consumer-grade software other than NEC-based. All FEM or FDTD software is proprietary and has no trial or demo.
There are many academic projects (like MEEP, sponsored by DARPA), which are Unix command line scripting tools. It will take you years of time to script bowtie antenna, run and interprete simulations.
 

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Is there a way to use necopt to try to minimize the gain for one target channel/direction, while maximizing other channels? I tried playing around but couldnt get it to wok.

gain only
Code:
CMD--OPT -s(174,6,8) --swr-target=2.7 -s(470,6,24) --swr-target=2
CMD--OPT --target-function "max(max_swr_diff, .2*ave_max_gain_diff+.8*ave_gain_diff)" -f "{174:(20,10),183:(68,-3),216:(180,-3),485:(2,15),500:(68,-2),506:(68,-2),533:(5,15),566:(68,-2),587:(10,15),593:(14,14),605:(14,14)}"
CMD--OPT --num-cores=3 -a15 --de-np=50 -r restart.log
one of my numerous failed attempts to add a negative target
Code:
CMD--OPT -s(596,6,2) --swr-target=2 --target-function "min_gain_diff" -f "{599:(35.5,-10)}"
CMD--OPT -s(174,6,8) --swr-target=2.7 --target-function ".8*max_gain_diff+.2*max_ml" -f "{174:(20,10),183:(68,-3),216:(180,-3)}"
CMD--OPT -s(470,6,24) --swr-target=2 --target-function ".8*max_gain_diff+.2*max_ml" -f "{485:(2,15),500:(68,-2),506:(68,-2),533:(5,15),566:(68,-2),587:(10,15),593:(14,14),605:(14,14)}"
CMD--OPT --num-cores=3 -a15 --de-np=50  -r restart.log
 

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I tried playing around but couldnt get it to wok.
It's not Python script fault, it is your wrong expectation on how antenna work.
You cannot make metal construction to have non-uniform radiation pattern over small frequency range (less than octave).

Less gain mean less directivity in main lobe and more directivity in other-than-main lobes. This is fundamentally impossible.
For stop-band rejection engineers use non-radiation-pattern-related techics with matching. At given frequency or band you implement notch-filter, pass-bamd, low-pass, high-pass etc. For unwanted frequencies it look like huge SWR. It can be implemented using lumped RLC elements, or their transmission line equivalents (microstrip, coax, symmetrical line, stubs etc)
They do not change directivity of antenna, only prevent energy from passing-through and force energy (wave) to reflect back where it came from.

Here is an example of most basic filter, which consist of only 1 element: L/4 transmission line open at the end (o.c. L/4 trline)
It is not usable for any practical solution, but show basic principle how filters work

Here is more practical application of the same principle:

This is more practical example of WiFi-notch filter + 1 GHz low-pass filter which is very common in TV tuners
 

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You cannot make metal construction to have non-uniform radiation pattern over small frequency range (less than octave).
actually this is possible to some extent.
if you add additional resonant elements (NAROD - not a reflector or director) to some (not many) designs - they may distort near field at some resonant frequency and hence distort far-field (directivity). This is common problem with patch antennas if you want to place something below patch. This something can have unwanted resonances and strong coupling to antenna at some frequencies. A few dB mainlobe decrease can happen.
 
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