I was referring to the Marconi 'Eznec can cook a fried egg on its own' brigade as an whole.
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The 5/8-Wavelength Antenna Mystique
- Thread starter Marconi
- Start date
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Yes 24, I figure 2010 compared both on the same pole like he said, and the top of the 1/4 wave was about 15' lower than the top of the 5/8 wave.
That is why the guys that did the real world test in the review...laid the antennas down horizontally about 1 wavelength high in order to help make the difference in height a non issue.
I posted some models once before suggesting what this laying down approach might do for the signals, and all the antennas produced signals that were very much closer to being the same vs. mounting them all at the same feed point height...where the taller antenna has a natural advantage with gain and sometimes with the angle.
That suggested to me, the longer antenna will still show a little advantage in signal, but just not the big advantage that theory suggest.
It is also likely that 2010's buddies all mount their antennas pretty close to the ground as well. Based on Cebik's list above, the taller antenna looks to have more advantage in getting the signals over obstructions on the Earth when both antennas are mounted low to the Earth.
Mounting 2010's antenna vertically on the same mount is the only reason that he might see the 3 db difference in signals he saw. Like I did, he could have mounted the two antenna at the same height to the current maximums, and then he likely would have seen far less of a difference. The review noted in this thread also suggested the 5/8 wave would not show a 3 db signal advantage in real world testing when compared with the antennas mounted on par and that is why they went to special measures to try and mitigate the effect for the height differences noted.
2010, again I ask, can you tell us how much difference in signals you see compared between these two antennas you mentioned?
I do have a recap report that covered reports 20, 21, 21A, 22, and 23. This recap covered many days of testing. Report 21A reported my A99 mounted at both mounting locations for comparison and the results are noted below.
This group of reports was selected at random, because here I was able to recap signals from my regular contacts with both antennas at the same height and on the same mount. These 5 reports were taken from other reports, and based on specific data collected from a select group of contacts and the factors noted above.
I selected test for the A99 and the I-10k both being on the same mount. I also selected other test for the A99 mount at my other locations. I compared those A99 reports and one mount reported 7.2 and the other reported 7.3 so I included them too and compared then to my I-10K report, because they were so close.
For information, I averaged the signals for each contact by adding the signals together, and then dividing the sum by the number of contacts. For the summing up process, if there was a sign after a number, I add a .5 to that number for a + located next to a number. I would minus a .5 from the number for a - sign next to the number. These reports with the + or - were noted when I saw the needle very close, but not quite touching the nearest number on the meter.
2010, you've probably already seen this recap below. I might even have a video or two posted somewhere for some of this testing, so you can at least see what I was attempting to do while testing...to collect signal data.
View attachment 091511 Recap Report.pdf
I was really surprised when I totaled this up and saw these two so close. I might have made some mistakes in recording some of this data, but over a period of time the this should all balance out to close to what I saw. This way I don't have to try and just remember what I saw and when I went back an recapped the data I could see the trends without just guessing.
I was referring to the Marconi 'Eznec can cook a fried egg on its own' brigade as an whole.
Nav, DB and I did get off track in this thread into a modeling idea he had about an Imax, but it was really a side issue.
This thread is not about anybody modeling, Eznec, or me. The only presentation of Eznec here was the comparison info I posted by Cebik, so we could see what he said about the issue.
I was probably working on my post about the same time. I see several post have been made, but you're right I haven't seen them yet.
Again, what kind of number differences are you seeing?
I posted where I thought I might have said something about my A99 doing well by comparision, but I didn't find it referencing all the antenna noted above. I also looked at all my recaps and I don't find what you claim here, excepting the one I posted.
Could this remark have been me talking about my Marconi made with 102" whips, an L bracket, and a A99 hub showing better signals on another recap?
There is no doubt that the half wave dipole works pretty well mounted high and away from the mounting pole, horizontally fed with a 2:1 balun to match the 75ohm impedance. The quarter wave would have a better potential if it can be decoupled from the mounting pole capacitively. Obviously the lower portion is angled and is a 50ohm impedance rather than the 75 but still needs to be decoupled from the mast and coax for it to perform well.
My experience against a Sirio 827 was a good S point+ difference at 25 miles mounted at 42 feet to the tips. Which is just short of the half wave's performance against the 827.
That is a standard quarter wave.
My thoughts are that the capacitive coupling between the mast/coax and the quarter wave's lower radiator needs to be gotten rid of. perhaps mounting the antenna on a 10 feet glass fibre pole on top of the mast and a method of horizontally feeding the coax.
Without this the quarter wave has a capacitive coupling to mast/coax which serves to detune the lower radiator and unbalance the whole job lot.
Marconi, it would be interesting to see two different models with this Eznec of yours.
The first model a standard quarter wave mounted at a tip height of 50 feet and the second a quarter wave mounted at 50 feet to the tip but this time mounted on a glass fiber mast and the coax fed horizontally at least a wave length long 90 degrees to the elements.
I would like to know (if possible) what Eznec says about decoupling (the conductive mast/coax and the lower radiator electrically).
The first model a standard quarter wave mounted at a tip height of 50 feet and the second a quarter wave mounted at 50 feet to the tip but this time mounted on a glass fiber mast and the coax fed horizontally at least a wave length long 90 degrees to the elements.
I would like to know (if possible) what Eznec says about decoupling (the conductive mast/coax and the lower radiator electrically).
Eznec does not provide a way to simulate a fiberglass element, but I can do that using empty space, so you won't be seeing a mast to the ground. I will try a feed line 90* degrees to the side that is 36' feet long + another length of about 42' to the ground. We'll see how this works.
Here is what I come up with Nav. I added an overlay of the two patterns too.
View attachment Nav's idea.pdf
View attachment Nav's idea.pdf
I see that you have modeled a Starduster and not a standard quarter wave.
Some strange shit going on there. Firstly if I have read it correctly, the decoupled antenna is one dbi of gain behind the standard model. I take it that Eznec has decided that the Starduster is transmitting on the mast and the coax because those two models should be at least identical or leaning towards the decoupled model.
If Eznec has indeed decided that the standard model is transmitting on the coax and the mast then I have some news for you - its not a quarter wave antenna. It could be anything from an inverted half wave to 7/8th wave, with the worst counterpoise is living history.
Some strange shit going on there. Firstly if I have read it correctly, the decoupled antenna is one dbi of gain behind the standard model. I take it that Eznec has decided that the Starduster is transmitting on the mast and the coax because those two models should be at least identical or leaning towards the decoupled model.
If Eznec has indeed decided that the standard model is transmitting on the coax and the mast then I have some news for you - its not a quarter wave antenna. It could be anything from an inverted half wave to 7/8th wave, with the worst counterpoise is living history.
Nav, I used the SD'r because its slanted down radials would at least be farther out of the way of the coax from the side mounted feed point. Aside from the SD'r, does this model look close to what you had in mind?
Your idea is not going to provide the decoupling for this antenna...even if the radials were horizontal instead of slanted down.
Your idea is not going to provide the decoupling for this antenna...even if the radials were horizontal instead of slanted down.
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If the mast is glass fibre and the coax fed at 90 degrees for a wavelength then it has no choice but to be decoupled simply because there is no conductive material to form a capacitive coupling with.
Hey Nav, I am curious as to what you were trying to show/prove with such a setup. Even a center fed vertical dipole that is fed with a coax will have some capacitance between the antenna and the coax shielding near the antenna. Just because it is 90 degrees off of the orientation of the antenna does not mean it will have no effect. Also, with the 1/4 wave vertical with horizontal groundplane you described, the outer shielding of the coax will react with the other horizontal elements in the groundplane and try to act like a ground plane radial itself. Even if you choke the RF off of the feedline at the feedpoint of the antenna, that is a line of conductance that is very close to some of the groundplane elements, which is also a radiating part of the antenna. This line of conductance will affect the radiation from said radials and at the very least throw off their balance, which will also affect the radiation pattern of the antenna.
The best direction to send the coax on a groundplane vertical antenna is straight down. This is true even if the radials are angled down (to a point). Let the radials do their jobs and help decouple the feedline from the rest of the antenna (among other things).
The DB
Nav, are you suggesting that this side mounted feed line should be 36' feet long, and terminate 36' above the Earth...and it will be fully decoupled?