-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Antenna Modeling Uploads
- Thread starter AudioShockwav
- Start date
Let me know if I missed any, or if anyone has any to add to this List.
Also, a link to this thread has been added to the Index.
73
Jeff
Also, a link to this thread has been added to the Index.
73
Jeff
so let me get this right... are we saying a i-10k with sloping 5/8 radials has 1.3db more gain than i stranded i-10k
Dave8, this model shows to me that the slanted down radials are about 22.5' feet long (5/8 wave).
Check out the red line indicated in the Antenna View for the first image. This red line is suggesting the actual magnitude of the currents flowing along the elements for this model. The farther the red line is away from the element...the greater the magnitude. You can easily see there is more current flowing on the mast here than on the radiator, maybe by double.
I don't know exactly what was going on when this was originally posted, but in this case it could be helpful if the these pdf files also provided us the link to the original thread. That way we might see a little context for the idea presented, and save us the trouble of trying to find it.
i see what you are saying Marconi, now that you have pointed it out....... so what will happen if the antenna was insulated from the mast
According to the model, it would tend to help decouple the mast from the antenna, but in the real world you still have the feed line connected...so you still have a current path to Earth.
Well Dave, according to most reports on the subject the use of a choke here will solve your problems. However, my real world results don't seem to support the idea as an easy fix. I have also been told that I got my chokes all wrong...else I would have seen the good results that I was expecting.
So, I'll leave any further commenting to 35's solution, and say you'll just have to try your own ideas, and see what you find.
Go to www.W8JI.com and read his reports on the subject. His approach is very detailed and complicated by math and measurements, but he claims in the end that a choke that is properly designed and installed will work to solve balance and common mode problems in association with good grounding designs, including the use of proper radials.
If you have a project in mind, give us some details.
I'd be skeptical of some of these models as I can clearly spot errors in a few. The Sigma IV at 36 feet looks nothing like the model posted with a peak gain over 45 degrees. The difference 12 inches in height makes at 37 feet is not even close to the reported 1.5 db. Way off on that one. The I-10K with slanted 5/8 wave radials has some issues too. How is it showing an extra db or more of gain with that intense mast / coax radiation that I'm nearly certain is out of phase with the radiator along the first half wavelength where the current is highest?
The 5/8 wavelength radials would also present a much higher driving impedance than the 1/4 wave radials. This should reduce the current flow in the 5/8 wave radials and their ability to decouple the mast or coax. That might explain why the currents on the mast / coax are actually higher than any other point on the antenna. It sure doesn't explain how the model shows improved gain though. This model would be more interesting to examine with the current phase option turned on.
The 5/8 wavelength radials would also present a much higher driving impedance than the 1/4 wave radials. This should reduce the current flow in the 5/8 wave radials and their ability to decouple the mast or coax. That might explain why the currents on the mast / coax are actually higher than any other point on the antenna. It sure doesn't explain how the model shows improved gain though. This model would be more interesting to examine with the current phase option turned on.
Shockwave makes a good point, which I've already addressed.
As I suggested earlier in response to this list of models in my post #2, for this thread: "...without the context for which these models may have been intended, nothing can be gleaned in looking at them, and that can lead to much misunderstanding...even though it is par for the course in the CB World."
Without context, these models are no better than wasting your attention on pictures written on a restroom wall in a truck stop.
Where are the models?
Why does anyone use the demo of ez-nec ? With only 20 segments and no variables. I confess I have not tried the program. I saw little reason to learn a program with those limitations.
I don't see any models. I see output reports from models. How can we get collaboration or peer review by posting only the results?
I'd also like to convince potential collaborators to use 4nec2 instead of ez-nec.
It can open ez files but ez cant open .nec files.
Further I think variables are a necessity when studying or updating legacy designs or just what-happens-if scratch design.
Why does anyone use the demo of ez-nec ? With only 20 segments and no variables. I confess I have not tried the program. I saw little reason to learn a program with those limitations.
I don't see any models. I see output reports from models. How can we get collaboration or peer review by posting only the results?
I'd also like to convince potential collaborators to use 4nec2 instead of ez-nec.
It can open ez files but ez cant open .nec files.
Further I think variables are a necessity when studying or updating legacy designs or just what-happens-if scratch design.
Jeff, thanks for pulling these together.
I do agree that if you could go back to the original post and provide a link back to the threads it would be additionally helpful.
Homer
I do agree that if you could go back to the original post and provide a link back to the threads it would be additionally helpful.
Homer
Hey 24, welcome to the forum. The first link in this thread was using Eznec Demo, and it is very limited in the number of segments you can use, but I use a next level of Eznec.
I've post results here, and maybe it was in vain, but I posted what I thought guys might be interested in and could possibly understand. Usually I was intending to be making some comparisons, but I think you're right it was mostly in vain.
I haven't looked at all the results posted above, but I think most of what is posted are stand alone results, and they are pretty useless...without some context for what their purpose was.
If you see any Eznec results of interest here that I may have posted or a CB antenna I might have, then let me know. I'll email you the .EZ files if I saved it.
I also have 4nec2. So, maybe you could help me get up to speed with that program. I realize a tutoring idea is not so easy to manage over the Internet as it may look, but I'm always willing to collaborate with my understanding of antenna modeling.
Good luck and hang in there, we need some more antenna modeling ideas here on this forum. I'm also looking for somebody to discuss Eznec's handing of currents and phase as well.
Hello Guys,
Modeling in its primairy stage should be done in freespace...
As that is the only way to illuminate all the other influences.
With that said, in some cases you need to model in "real live"
example are: take off angle/ RF currents along a mast etc.
However those should be classified under "special cases".
And the "modeler" really should express....these special cases....so others with NO knowledge understands how "not" to interpertate them.
As it is easy to "fool".... guys like array solutions sell 1600 dollar CB antennas with 16..17 dB gain..(and they are right...but they add ground gain so you can subtrackt say..6 dB).
The eznec demo program is perfect for handeling small antennas.
Like dipoles, but as soon as the antennas become large (more metal in the air) you should need a version which handles more segmentation.
With that said...4nec2 handels a lot of segmentations..is free...and has the the same limitation that enzec (nec2) has.
MMana is also free has a large number of segmentations...and uses mininec which is in some case more accurate compared to nec2. (eznec/4nec2)
And there are more things to consider..The average gain factor etc.
In my opion it is not wise to "upload" everything...un less you have done your best to make sure it is not interpertated wrong by others....
And the one who does the modeling should be aware there migth be those who are less knowledgable...heck there are those who do modeling...let say....with room for improvement.
Regarding those phase currents thingy..
I am more than willing to help...but what is it you do not understand ?
As i have done quite some effort in the past and i hate when i am unable to explain it so people do understand. (not your fault !!!)
Kind regards,
Henry
ps havnt put that sigma 4 in cst yet...but will come..when time permitts...already 23.30 local again...so off to bed.
Modeling in its primairy stage should be done in freespace...
As that is the only way to illuminate all the other influences.
With that said, in some cases you need to model in "real live"
example are: take off angle/ RF currents along a mast etc.
However those should be classified under "special cases".
And the "modeler" really should express....these special cases....so others with NO knowledge understands how "not" to interpertate them.
As it is easy to "fool".... guys like array solutions sell 1600 dollar CB antennas with 16..17 dB gain..(and they are right...but they add ground gain so you can subtrackt say..6 dB).
The eznec demo program is perfect for handeling small antennas.
Like dipoles, but as soon as the antennas become large (more metal in the air) you should need a version which handles more segmentation.
With that said...4nec2 handels a lot of segmentations..is free...and has the the same limitation that enzec (nec2) has.
MMana is also free has a large number of segmentations...and uses mininec which is in some case more accurate compared to nec2. (eznec/4nec2)
And there are more things to consider..The average gain factor etc.
In my opion it is not wise to "upload" everything...un less you have done your best to make sure it is not interpertated wrong by others....
And the one who does the modeling should be aware there migth be those who are less knowledgable...heck there are those who do modeling...let say....with room for improvement.
Regarding those phase currents thingy..
I am more than willing to help...but what is it you do not understand ?
As i have done quite some effort in the past and i hate when i am unable to explain it so people do understand. (not your fault !!!)
Kind regards,
Henry
ps havnt put that sigma 4 in cst yet...but will come..when time permitts...already 23.30 local again...so off to bed.