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  Topic Review (Newest First)
2019-06-23 04:23 PM
holl_ands
Quote:
Originally Posted by yankeeindixie View Post
holl_ands, I've begun running the nec software following majortom's instructions. I started reading the nec user manual. I've learned that my ideas for L or square shaped elements would produce something that would be quite different from what you guys have modeled, so I am going to abandon those ideas.

A1: Yup....NEC2 is primarily a Cylindrical Wire type model....although it does half-way support Flat "Patches"....but since you can't SEE them in 4nec2's Geometry Viewer, I avoid them like the plague. And as I said, "L" and "U" shaped extrusions will have a LOT higher wind resistance as they "cup" the wind.....although not as much an increase as square shaped extrusions. BTW: Hollow Alum. Rods would also be easier to bend...although I've tried to point you in the direction of designs that do NOT require any (or very little) bending....incl. Square Loop Folded Dipoles using Angle Connectors with either copper or aluminum type solder.

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.

A2: Although I've built a few DIY Antennas for my own use, I'm an Antenna Designer....NOT in the Antenna Construction Business.

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?

A3: Although I've built a few DIY Antennas for my own use, I'm an Antenna Designer....NOT in the Antenna Construction Business.

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?

A4: Not much difference from an electrical performance viewpoint, only minor effect, esp. SWR, seen in UHF Band.

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.

A5: Yes, it's a viable alternative. I have uploaded over 800 different Antenna Designs and simply can't remember everything I've done. I try NOT to replicate what nikiml has done on his (mostly G-H) website, nor Ken Nist on his HDTVPrimer [mostly old] Antenna Analysis website, nor K6STI on his FM (and a few other) Antenna Design Website. The few G-H designs you might find on my imageevent website were either from the early days (pre-nikiml), in response to a posted candidate G-H design variation or because I wanted to generate a performance Curve for inclusion on a Comparison Chart. The UHF SBGH + 2ea 36"x18" Screen Grid Refl Design was a rare exception, per the request of a particular user:
https://imageevent.com/holl_ands/gra...screengridrefl

See my embedded comments....

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
majortom 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
majortom
Quote:
Originally Posted by yankeeindixie View Post
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?
Whatever works in your environment.
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
yankeeindixie
Quote:
Originally Posted by holl_ands View Post
I've looked at a LOT of user installation reports, but I do NOT recall ANYONE using Angle Extrusion rather than Circular Rods. Obviously, Angle Extrusions would have a MUCH higher wind resistance....and may or may NOT break sooner than Rods....it would depend a LOT on the inherent strength of the chosen metal formula....I would ALSO be worried about how it holds up to wind induced vibration.

Since an outdoor antenna needs to survive high winds [esp. in your location], I would highly recommend that you stick with what we know WORKS...namely 3/8-in Aluminum Rods.
holl_ands, I've begun running the nec software following majortom's instructions. I started reading the nec user manual. I've learned that my ideas for L or square shaped elements would produce something that would be quite different from what you guys have modeled, so I am going to abandon those ideas.

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
yankeeindixie
Quote:
Originally Posted by majortom View Post
Download Nikiml's python scripts, the linux tarball.
nikiml's Antenna pages - Nec optimization scripts

and follow the installation instructions..
nikiml's Antenna pages - Nec optimization scripts

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.
nikiml's Antenna pages - nec.opt tutorial

say ./nec_eval.sh gh0.nec for example.
majortom,
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
rabbit73
Quote:
Originally Posted by yankeeindixie View Post
Where and when was there a track in Kingston? That one I don't remember.
I'm 86, so I'm about 20 years older than you.

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
rabbit73
Quote:
Originally Posted by yankeeindixie View Post
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?
In the ten years that I have been doing this, I have learned a few ways to estimate a poster's location. The more I know about the reception location, the better I'm able to help the poster. Sometimes I will ask the poster for his address and antenna coordinates in a PM to protect his identity. With that information, I am able to look at a satellite view and sometimes a street view, just as if I were there to help him.

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
holl_ands 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
yankeeindixie
Quote:
I think you might be from RI. We used to visit relatives in Weekapauge, and my father took me to my first stock car race in Kingston.
One of the Boy Scout camps we went to was in Weekapauge, not sure of the correct spelling, but it was called Aquapauge. (I'm guessing that if folks aren't from around there or are not familiar with the Narragansett Indians, they'll pronounce thouse incorrectly.)

Where and when was there a track in Kingston? That one I don't remember.
2019-06-21 11:06 PM
yankeeindixie (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
majortom
Quote:
Originally Posted by yankeeindixie View Post
majortom,
I've installed the three packages that you provided. What's next?
Download Nikiml's python scripts, the linux tarball.
http://clients.teksavvy.com/~nickm/s....html#download

and follow the installation instructions..
http://clients.teksavvy.com/~nickm/scripts.html

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.
http://clients.teksavvy.com/~nickm/s..._tutorial.html

say ./nec_eval.sh gh0.nec for example.
2019-06-21 07:49 PM
rabbit73
Quote:
Originally Posted by yankeeindixie View Post
holl_and, here is a link to the RabbitEars report that I ran. It seems very much like what rabbit73 posted.

https://www.rabbitears.info/search.p...=dBm&height=30

rabbit73 must've used some voodoo that I'm not aware of, to get a much more accurate location for where I'm at. The map he posted shows it just about dead nuts on. I'll guess that the discrepancy in the signal reports you were looking at are due to location differences. I'm not sure what a straight line distance from my house to the post office is, but driving distance is about 15 miles. Closest convenience store to me is 9 miles driving. There are literally more critters around me than people.
Thank you for the new link. My original guess was off by about 400 feet at the house just south of you in from the road and surrounded by trees. Your house in more in the open, especially from the south.

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
rabbit73
Quote:
Originally Posted by yankeeindixie View Post
WOR. For some reason those call letters sound familiar, but I don't remember where they are located.
WOR is considered a New York (city) AM radio station on 710. When I was a kid, its transmitter was in Carteret NJ, and I lived in a small town between New Brunswick and Perth Amboy which makes me a yankee too. I think you might be from RI. We used to visit relatives in Weekapauge, and my father took me to my first stock car race in Kingston.
Quote:
Is WOR that AM station that used to advertise serving X number of States and 3 Countries?
Probably; it is a 50,000 Watt Class A Clear Channel station.
2019-06-21 03:03 PM
yankeeindixie holl_ands,

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
yankeeindixie
nec2 Software

majortom,

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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