|Topic Review (Newest First)|
|2019-06-23 04:23 PM|
Note that nikiml and I have very DIFFERENT Antenna Design Objectives....he tries to find the highest GAIN with an acceptable SWR, and allows the F/B & F/R Ratio performance to be whatever it wants to be, cuz it is NOT included in his "Target Function". OTOH: I almost always TRY to design an Antenna with significant F/R (Front/Rear) Ratio performance [F/B, Front/Back is always higher since it is a sub-set of F/R for the very narrow angle directly to the "Back"]....and do several re-runs until I am happy with keeping SWR Max at JUST under an acceptable value of 2.7, which provides final maximization for Gain.
So, my UHF SBGH provided about 1 dB lower Gain, but 10 dB higher F/R & F/R Ratio performance. BTW: I've done numerous Designs with choice of either Flat Grid Reflector or Multiple Reflector Rods....the latter consistently provides higher Gain, although many are needed to match the F/R Ratio performance of the Reflector Grid (Flat or Folded).
BTW: If "someone" were to re-optimize any of nikiml's G-H designs using my type of "Target Function" [incl. with Grid Reflector], they could tailor the Gain/MismatchLoss/F_R/F_B "weighting" factors to emphasize and de-emphasize the design parameters as desired. Here is an example of my most commonly used nikiml OPT and EVAL Control Statements, incl. initial "Target Function"....before I "tweak" it as the design evolves:
[PS: "f2b_d iff" should be "f2b_diff".....something gets hozed when I copy/paste it.]
CMD--OPT -s(470,6,24) -t(13,14) --swr-target=2.7 --f2r-target=15 --f2b-target=15
CMD--OPT --target-function=(2*max_ml+8*max_gain_diff+4*max_f2r_diff+max_f2b_di ff)/15
CMD--OPT --de-np=50 -r restart.log
CMD--OPT --auto-segmentation=11 --char-impedance=300 --num-cores=12
CMD--EVAL --auto-segmentation=0 --char-impedance=300 --num-cores=12
CMD--EVAL -s(174,3,15) -s(470,6,39) --total-gain --publish
|2019-06-22 06:01 PM|
I use copper wire for dabbling with antenna elements, since it bends easily.
It can also be straightened rather easily, by tying one end off in a vice, or some other means to anchor.
put the other end in the chuck of a drill, and let the drill run to twist the wire until it is perfectly straight. Makes for good stock to bend elements with.
|2019-06-22 05:21 PM|
The reason for 'python2' in mine was to be more specific.
eg - in linux OSs, there's legacy python2, and newer python3
if the user doesn't specify, the system decides based on what you had configured to be the default python environment in your environment variables.
Nikiml uses python, because it's a powerful scripting language, suitable to parse the NEC2 program's card deck inputs, program output results, automating the process of analyzing.
I agree, a separate topic covering NEC2, Nikiml's scripts, and 4nec2 in linux would be a good idea.
But we already started it here so...
Maybe you can give a moderator a heads up (report Post Tool is the 'warning icon' to the left of a post) and they can 'Spilt" the relevant posts from this thread in to a new thread for you.
|2019-06-22 02:07 PM|
Originally Posted by holl_ands View Post
About the aluminum rod; is it easily bendable? One on-line supplier's site I looked at indicated that forming and bending characteristics were poor.
How do you guys go about mechanically joining shorter pieces? The longest piece I can buy locally is 48" and the driven elements for what you recommended are longer than that. Where do you guys get your aluminum wire from?
From reading the software user manual, I can see there will be a difference between copper and aluminum, but in a practical sense will it make that much of a difference? Can I combine the two in the same antenna? Can I use copper for the driven elements and aluminum for the reflectors?
Looking at the channel reports from the two different sites, I see a problem with WPGX. One site shows I should get a good signal while the other shows a poor signal. It looks like its the only VHF channel I should be able to get. So I think I'll start with a UHF only antenna and see what happens.
I was looking through your site last night. You have UHF SBGH + 2ea 36"x18" Screen Grid Refl listed but you didn't offer that as a recommendation; I'm wondering why? Using the screen as a reflector seems as if it would be easier to construct (I like easy). Is this a viable alternative? If so, I think I might try this one first.
|2019-06-22 01:20 PM|
Originally Posted by majortom View Post
I don't know how far you are willing to go in helping me with the operation of the software, at each stage of this process, I'm coming up with more questions. I'm wondering if I should start a separate thread for this if you're willing?
I followed your instructions, read nikiml's tutorial and then let the script run to completion. While it was running, I followed the link from nikiml's site to the user guide and began reading that (still have a ways to go).
python vs python2
in nikiml's nec-eval.sh script mikiml calls python while you call on python2. I have both installed; does it make a difference? I ran your copy, using the python2. You did not give me an nec_opt.sh script, so I used nikiml's copy which calls python. Can I combine the two like this or should I stick with one and if so which one?
Now I have (as they say here in dixie) a mess of files, what do I do with them? How do I produce the graphical files showing the antenna structure with dimension and the plots for the beam?
A question about this process. Why are we using python? Is it because nec can't read the input file directly and we don't want to maunually input each line over and over? In essence, is python providing the input to nec, capturing nec's output, then sending it back to nec for the next iteration?
(I really need to get a life, I was up to 2AM watching the computer loop and reading; before deciding the computer could run just fine without me watching, and went to bed.)
|2019-06-22 12:32 PM|
The most popular car used was the 1936 Ford coupe. I remember the hood of one car flying open during a race, but the driver could still see through a small space just above the bottom of the windshield.
Kingston is a village and a census-designated place in the town of South Kingstown, Rhode Island,
United States, and the site of the main campus of the University of Rhode Island.
Racing started at the Lonsdale Sports Arena in Cumberland, then moved to the Kingston Fairgrounds in South County. Washington County, known locally as South County, is a county located in the U.S. state of Rhode Island.
|2019-06-22 11:58 AM|
In your case, you gave me some clues in your posts and a TVFool report which I combined with a Google search.
I would rather not go into greater detail about my methods because I want to adhere to the same standards used by TVFool to protect a poster's identity.
|2019-06-21 11:22 PM|
FYI: When someone posts a TVFool Report based on their street address [or accurate Lat/Long], then it's a fairly easy trial-and-error process to enter their zipcode (if provided....or a nearby zipcode) into TVFool's "MAP" Search feature and grab/move the location Icon until the reported Distances to multiple Transmitters [best if separated by about 90-deg] match his posted Report [accurate to 0.1-mi].....the process is called Reverse Bi-Lateration.
In the past, I've asked for a user's city or zipcode and nearest cross-streets and then used GoogleEarth or GoogleMaps [Right-Click "What's Here"] to determine approx. Lat/Long for entry into TVFool.
|2019-06-21 11:21 PM|
Where and when was there a track in Kingston? That one I don't remember.
|2019-06-21 11:06 PM|
(Being new to the forum I clicked on the quick reply button in rabbit73's post, I thought this would end up next to that post. This one is directed at post #s 14 & 15)
I'm replying to both of your recent posts about me. Not Voodoo hungh? I ain't speaking out loud so you can't hear my accent. How did you figure out where I am from? Do we know one another; have we met somewhere?
Yes, I am originally from RI, so WOR being out of NY is probably why its familiar. The other station I was thinking about is located somewhere in the middle of the country. I first learned of it when spending time in OK. From what I remember about it, it was the only station on that AM freq, so they were allowed to use the maximum amount of power to transmit. Their signal spaned across the country and went into Canada and Mexico, so it was all the States inbetween.
|2019-06-21 08:58 PM|
and follow the installation instructions..
After it is done, u'll probably want to edit this bash script and make it executable
'chmod +x nec_eval.sh'
here is mine...
[[email protected]]: ~/src/nikiml>$ cat nec_eval.sh
python2 -m nec.eval --validate-geometry=0 -e nec2 $*
I would then copy some examples that have been edited to be used with nikiml's python scripts
in to the same directory where that bash script lives and run it.
He has an example in his tutorial you can follow along and use.
say ./nec_eval.sh gh0.nec for example.
|2019-06-21 07:49 PM|
It's not voodoo, it's practice. I have been doing this for about ten years, with 7,494 posts on four forums, and consider it a challenge to solve the location puzzle. The more I know about the location, the better I'm able to help a poster with a reception problem.
|2019-06-21 07:31 PM|
|2019-06-21 03:03 PM|
I still have a scar on the inside of my left ankle. Sometime, when I was in High School, I received a HeathKit, for an AM Shortwave receiver. It actually turned out pretty nice and I used it for years.
While building it, I was wearing a pair of hiking boots that were not laced up. A ball of solder feel off the iron and it landed on the inside of my boot. Did you know you can not remove molten solder from inside your shoe until it has cooled enough to become solid again?
|2019-06-21 02:29 PM|
I've installed the three packages that you provided. What's next?
From a discussion about a Finco 400 clone antenna, I copied what I was calling the in-line file and used that as an input file to the nec2 program.
nec2 Finclone400-A.nec (the filename I made up myself)
this is the result of that command
GEOMETRY DATA CARD ERROR
CM Finco 400-ww with reflectors project in works
Then I'm returned to the promt.
The man page says if an output file is not specified, output goes to stdout. I was expecting something on the screen.
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