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VORTEX Q82 mk2
- Thread starter bob85
- Start date
Taper with the right tube diameters would be nice Eddie, it may show wider bandwidth,
i would like to know why you have such a discrepancy in gain,
until i learn differently your gain figures make more sense going on what we have learned over the years about that style antenna,
my sigma has 10 tube sections 1 - 5/8" > 1/2" plus 7" x 1 - 9/10" base tube.
i would like to know why you have such a discrepancy in gain,
until i learn differently your gain figures make more sense going on what we have learned over the years about that style antenna,
my sigma has 10 tube sections 1 - 5/8" > 1/2" plus 7" x 1 - 9/10" base tube.
Typically, yes, more bandwidth at the cost of some gain, however, unless the diameter difference is pretty extreme it won't make that much of a difference in bandwidth of gain.
Not necessarily. The j-pole, for example, has almost no radiation from the matching stub area because the currents on each side of the stub are nearly equal and opposite, i.e. in balance. Change the area of the stub, however, and that changes. If you put a 3/8 wavelength vertical on top of the j-pole the stub will no longer be in balance, and this imbalance will cause the stub to radiate. The same thing will happen with the Vector style antennas.
The model I made on it a while back agreed with this.
I had the idea of doing this with a 1/4 wavelength antenna in the past. In models I just played with it does make a difference that I can barely see. Here are some examples using 1/4 wavelength antennas and angled radials.
Same length radials.
Radials with minimum 1 inch difference in all radial lengths (i.e. 102, 103, 104, 105 inches)
Radials with minimum 2 inch difference in all radial lengths (i.e. 102, 104, 106, 108 inches)
The difference between these three SWR curves is not a significant enough of a difference to notice. I just don't see the small change that you are going to have on the Q82 antenna making enough of a difference to notice.
If you are looking to create a noticeable change in bandwidth, then you need a much larger difference in radial length. Here is a 1 foot minimum difference in radial length (i.e. 7 8 9 and 10 foot radial lengths).
So we now gained 1.5 MHz in bandwidth over all of the above models, which in and of itself isn't bad, but it took a very significant difference in radial lengths to achieve this, a 3 foot difference between the shortest and longest, and the other two spaced evenly within that range.
The concept of varying the length of radials to increase an antennas bandwidth isn't wrong, but the amount of variance needed to achieve anything noticeable is more than most people who have the though realize.
The DB
So Bob, maybe taper and using longer elements are, as you suggest, a broad bandwidth technique. However, Vortek didn't use taper and still got a big gain and shows a very wide bandwidth. This does not mean that taper has NO effects...but like a lot of claims in the CB world...it turns out the effects appear to be very small.
So Bob based on this, I don't trust my models results either. However, I do question if it is the taper making the difference we see in bandwidth and gain. My model didn't use taper and it shows the broad bandwidth but the gain is less.
Vortek didn't use taper and they still reported a wide bandwidth and a big gain...so go figure.
If my model of the Mark2 showed the big gain reported...you can bet I'd be touting this new design.
My manual for the Avanti S4 and my Antenna Specialists both show the same tubing lineup for the radiator, and they both show 9 tubes from the very bottom, including the mount, to the top.
If I got this wrong Bob, hopefully DB can explain better. I have never tested or compared the idea for taper...maybe that might show a difference but I have my doubts the results would be as significant as suggested in the Mark2. IMO, I think the wide bandwidth is primarily due to the much taller basket. That is not to suggest that taper does not have an effect in this case, but if it does it would appear, at this point, to be a small difference.
Henry uses taper in some of his beam antennas. Maybe I'll model one of his beams, if I can find one that hopefully still shows the wire descriptions. Maybe then I'll have something to compare and report.
So Bob based on this, I don't trust my models results either. However, I do question if it is the taper making the difference we see in bandwidth and gain. My model didn't use taper and it shows the broad bandwidth but the gain is less.
Vortek didn't use taper and they still reported a wide bandwidth and a big gain...so go figure.
If my model of the Mark2 showed the big gain reported...you can bet I'd be touting this new design.
My manual for the Avanti S4 and my Antenna Specialists both show the same tubing lineup for the radiator, and they both show 9 tubes from the very bottom, including the mount, to the top.
If I got this wrong Bob, hopefully DB can explain better. I have never tested or compared the idea for taper...maybe that might show a difference but I have my doubts the results would be as significant as suggested in the Mark2. IMO, I think the wide bandwidth is primarily due to the much taller basket. That is not to suggest that taper does not have an effect in this case, but if it does it would appear, at this point, to be a small difference.
Henry uses taper in some of his beam antennas. Maybe I'll model one of his beams, if I can find one that hopefully still shows the wire descriptions. Maybe then I'll have something to compare and report.
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Bob, I also compared the maximum currents in amps at the peak on the radiators for my NV4K vs. Mack2. You will see the Vector has about 31% more current at the peak.
The print is quite small, you may need to use the "+" function to zoom in close. Check at the top of the PDF file to zoom.
The print is quite small, you may need to use the "+" function to zoom in close. Check at the top of the PDF file to zoom.
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Bob here is a link to Henry's Maco 103C model: http://www.dx-antennas.com/MACO M103C.htm
You will notice in Henry's wires description image...that he used taper in all 3 of his elements. You can also see the segment connection points (blue squares) on the wires in his antenna image.
Below is a PDF file of my Maco M103C with no taper. All wire are 1/2" inches.
There is little to no difference between our models due to using taper. The performance details noted in our images are almost identical.
You will notice in Henry's wires description image...that he used taper in all 3 of his elements. You can also see the segment connection points (blue squares) on the wires in his antenna image.
Below is a PDF file of my Maco M103C with no taper. All wire are 1/2" inches.
There is little to no difference between our models due to using taper. The performance details noted in our images are almost identical.
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Eddie,
im not saying taper changes bandwidth by any notable amount,
as we know conductor diameter does but not much,
id be more concerned about diameter & spacing with regards to impedance if you are looking for a good vswr.
maybe DB or Henry can figure out where Vortex get the 5.8db gain from, i don't understand models to see what they did,
If it were true all you would need do is make a less agricultural version of it and you have the best vertical out there.
im not saying taper changes bandwidth by any notable amount,
as we know conductor diameter does but not much,
id be more concerned about diameter & spacing with regards to impedance if you are looking for a good vswr.
maybe DB or Henry can figure out where Vortex get the 5.8db gain from, i don't understand models to see what they did,
If it were true all you would need do is make a less agricultural version of it and you have the best vertical out there.
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DB
There's always some radiation from the j-pole stub skewing the pattern due to one side been connected to the end impedance of the radiator while the other is connected to fresh air,
Cebik said wider stubs tend to radiate more, he also did some j-pole models with different stub lengths & to my eyes it did not make as much difference to the pattern as i expected,
years ago when i was playing with the vector hybrid radials + monopole leghths i said because the monopole was longer than 3/4wave the top of the sleeve is not seeing the bottom of a 1/2wave so the unbalance will be greater causing the sleeve to radiate more than it would when used with a 3/4wave monopole,
you are the first person to agree.
There's always some radiation from the j-pole stub skewing the pattern due to one side been connected to the end impedance of the radiator while the other is connected to fresh air,
Cebik said wider stubs tend to radiate more, he also did some j-pole models with different stub lengths & to my eyes it did not make as much difference to the pattern as i expected,
years ago when i was playing with the vector hybrid radials + monopole leghths i said because the monopole was longer than 3/4wave the top of the sleeve is not seeing the bottom of a 1/2wave so the unbalance will be greater causing the sleeve to radiate more than it would when used with a 3/4wave monopole,
you are the first person to agree.
Bob, I don't have a clue what an agricultural version might mean unless you're referring to "homebrew."
Here is my contribution to this dilemma. I'm not sure I can explain this model in understandable words, but first I'll wait and see what Steve or Henry have to add.
I recently mentioned, in a post about a similar situation of a really high gain model I made. I think I was talking to DB regarding an A/P with/without the blue line. That model showed very high gain in Free Space and over Real Earth. I said at the time, "...this is was impossible." I posted the model, but don't recall DB's or anybody else responsing.
IMO it is possible to show ridicules results if a body has a mind to puff-up their product or idea. I went way overboard in this model to show it can be done.
This model indicates the important dimensions at the bottom of the antenna view. The performance results are included, SWR bandwidth, pattern, and match all look similar to my posted model at 27.500 MHz which shows 3.63 dbi at 8* degrees.
Model was deleted.
Here is my contribution to this dilemma. I'm not sure I can explain this model in understandable words, but first I'll wait and see what Steve or Henry have to add.
I recently mentioned, in a post about a similar situation of a really high gain model I made. I think I was talking to DB regarding an A/P with/without the blue line. That model showed very high gain in Free Space and over Real Earth. I said at the time, "...this is was impossible." I posted the model, but don't recall DB's or anybody else responsing.
IMO it is possible to show ridicules results if a body has a mind to puff-up their product or idea. I went way overboard in this model to show it can be done.
This model indicates the important dimensions at the bottom of the antenna view. The performance results are included, SWR bandwidth, pattern, and match all look similar to my posted model at 27.500 MHz which shows 3.63 dbi at 8* degrees.
Model was deleted.
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It can be any number of things, however they all boil down to two real options of which it can be one of both. A screw up for instance, which would suggest incompetence. The other is intentional misleading, which would be malice.
Unless I have evidence to the contrary, I follow Hanlon's Razor when it comes to choosing between these options.
This is correct, where on one side of the stub you have a tip going to air, on the other you have a continuation of the metal. One will create a voltage peak that has no current flow and the other will create a voltage peak that still has some current flow. As these are two different situations, their will be an imbalance between the current flowing on the two sides, and thus you have some radiation from the stub.
I'de have to see the models in question. If he kept the radiating section at 1/2 wavelength no matter what he did with the stub, then the current on the two sides of the stub would look similar if not the same.
I can show what I mean. This, to start, is the current distribution of a j-pole type antenna.
From here, it doesn't matter how much I change the length of the stub, the current distribution is largely the same on both sides. Here we have a 1/8 wavelength stub.
However, if I change the length of the 1/2 wavelength element above the stub instead, this is no longer the case. Here is a j-pole with a 1/4 wavelength stub and the radiator has been shortened to about 3/8 wavelength.
I am the first person to agree with this? I find this surprising.
I remember your post on that, and you are right, I didn't respond. Having very high gain like that is a model I would have either investigated it or thrown it out, depending on what I was looking for at the time. Generally when I get unexpectedly high or low gain numbers it is due to a mistake in the wire layout of the model and can be fixed.
It is very easy to create a model that will vastly over report gain. I could create a model of virtually any antenna and make the gain for that antenna whatever I want it to be, however that model will be useless. At one point I posted a Vector model that had over 1000 dBi in gain. Posting a BS model is easy, ensuring the model is accurate requires a little more work.
The DB
DB, Bob asked this question, and I recalled my model, I mentioned above. It did something similar. My posting this model was simply to suggest...that it is possible to inflate a model.
Excepting for this exception, I would not have posted such a model for the same reasons you suggested. You and I both know the model being review is impossible and is in error showing the gain reported, but I wonder about others including Dave who might be convinced by the promotion.
I guess you missed my point, so I removed the model for fear I will be accused of posting tricked-out models.
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I didn't miss your point Eddie, I was just stating that most people just throw stuff in and don't do any checking for accuracy, and some actively manipulate said models, which you and I both know isn't hard to do. As far as I know you don't do that. My statements were aimed more at Vortex Antenna Systems, and any manufacturer of antennas.
Its fine to post said models if you are making a point, just be open about them, and don't be surprised if I ignore them as I generally see them as being irrelevant.
The DB
Its fine to post said models if you are making a point, just be open about them, and don't be surprised if I ignore them as I generally see them as being irrelevant.
The DB
Your saying my example of a possible bad model is irrelevant is fine with me, but a lots of folks might be convinced by the pretty pictures.
When it comes to the tapering discussion above. I know how to use it with 4nec2, but I really don't. The results when it comes to gain and SWR bandwidth will be somewhere in between the two diameters depending on where the current peak happens on said wire. In most cases the two diameters in question produce results that are very close to each other to begin with.
You can also use tapering to actually vary the length of segments along a wire as well, essentially more segments on one side and less on the other side of a given wire. While I can see the potential in this, I don't need it as I use enough segments in general to account for this to begin with. If I had a segment limit I would likely use this feature.
The DB
You can also use tapering to actually vary the length of segments along a wire as well, essentially more segments on one side and less on the other side of a given wire. While I can see the potential in this, I don't need it as I use enough segments in general to account for this to begin with. If I had a segment limit I would likely use this feature.
The DB