The other day Bob and Shockwave were talking about the J-Pole. Bob suggested for us to check the Internet for some J-Pole models to see how the J-Pole skews the pattern. It sounded bad to me and I went on the Internet to check. I found a model describe in an article that W8JI published on his Website and this link is noted below.
The model included the Wires window that is the data entry for Eznec modeling program, so I thought I would see if I could use this information to duplicate his model. My idea was to help explain some questions I had, and for some others on another thread entitled "Homemade Sigma 4 11 meter base antenna." I decided build the model and use it to help demonstrate some issues in question if I could...like how the J-Pole skews the pattern, and which elements in the bottom of the antenna are in-phase and which are not.
In the process of building the model I found two errors that affected the results the article talks about. So, I decided I would fix the errors and present both models as a demonstration of the problems, and in due-course maybe help explain the questions asked earlier.
Below are the two 2 meter models and some images from the article by W8JI: End-fed Vertical and J-pole.
Shockwave I added some notes and the Wires window, along with the tabular Currents log in order to indicate a trick that W8JI uses to allow Eznec to show currents properly. In my efforts to build a J-Pole I could never get the currents to work right, but I was not doing a simple thing right. I will describe this for you, but see if you can figure it out for yourself first, OK? We discussed this issue before in emails, but we did not come to any agreement or good conclusions...except that Eznec did not work as intended.
As a note both of these models have the red line currents turned ON. Note that elements that are in-phase are on the same side of the image and visa-versa.
I do not know if the errors were intended to show something special to the reader or not. As usual in some of these type writings, there is not enough information for a really good understanding unless maybe the reader is really well-up on the technical aspects of two-way radio, but this is what I found.
Take note that the original antenna's mast does not go all the way to the ground and that it is off-center and not straight. The antenna is set at 13.333' above ground and the mast is only 60.12" tall.
I made no efforts to try and duplicate the worst case scenario W8JI talks about briefly either.
I added some notes, but if you have question, just ask.
View attachment W8JI's 2m J-Pole.pdf
The model included the Wires window that is the data entry for Eznec modeling program, so I thought I would see if I could use this information to duplicate his model. My idea was to help explain some questions I had, and for some others on another thread entitled "Homemade Sigma 4 11 meter base antenna." I decided build the model and use it to help demonstrate some issues in question if I could...like how the J-Pole skews the pattern, and which elements in the bottom of the antenna are in-phase and which are not.
In the process of building the model I found two errors that affected the results the article talks about. So, I decided I would fix the errors and present both models as a demonstration of the problems, and in due-course maybe help explain the questions asked earlier.
Below are the two 2 meter models and some images from the article by W8JI: End-fed Vertical and J-pole.
Shockwave I added some notes and the Wires window, along with the tabular Currents log in order to indicate a trick that W8JI uses to allow Eznec to show currents properly. In my efforts to build a J-Pole I could never get the currents to work right, but I was not doing a simple thing right. I will describe this for you, but see if you can figure it out for yourself first, OK? We discussed this issue before in emails, but we did not come to any agreement or good conclusions...except that Eznec did not work as intended.
As a note both of these models have the red line currents turned ON. Note that elements that are in-phase are on the same side of the image and visa-versa.
I do not know if the errors were intended to show something special to the reader or not. As usual in some of these type writings, there is not enough information for a really good understanding unless maybe the reader is really well-up on the technical aspects of two-way radio, but this is what I found.
Take note that the original antenna's mast does not go all the way to the ground and that it is off-center and not straight. The antenna is set at 13.333' above ground and the mast is only 60.12" tall.
I made no efforts to try and duplicate the worst case scenario W8JI talks about briefly either.
I added some notes, but if you have question, just ask.
View attachment W8JI's 2m J-Pole.pdf
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