Base Should I stick it?

[binrat]

When I first found this antenna I thought it was the answer to my prayers for that very reason. With my steeply pitched roof and relatively short mast (15') full-length radials just aren't going to work. However, from what I've heard it doesn't handle strong winds very well and here in Texas we get some humdinger thunderstorms with gale force winds. Often.

Well there is only 1 thing to do. Make an improved RM71 approved 1.
Before I moved west I built 1 which lasted through numerous 60-80 kph winds with freezing rain. Only had it about 30 feet as I was not going to put it up high at top of pipe on tower.

 

[br549]

wouldn't be at all good for that location . you could make one that's much more durable . i'm suprised the big brained "CB" antenna manufacturers aren't making them , if folks are willing to pay several hundred dollars for a 5/8 it seems that they would pay just as much for a vertical that's even better ? surely those "manufacturers" don't find it too difficult to build . since many folks make their own to suit their climates they couldn't be too difficult for a "real" antenna maker to clone a beefier version .or sirio could do it and double their asking price , would still be almost half the price of some of those 5/8 sold to CB'ers .

 

[The DB]

Did you also try modelling it, as Henry mentioned, at 2-3 wavelengths above ground? Mine is only 36' to the radials.

I moved it up just because you asked, when it comes to gain, their was no real difference in my results.

DB
im not sure what software Henry used to determine signal strength,
i think he has talked about it on here,

its not almost 2db extra gain as you won't get that from a co-linear like the BIG-MAC or Henry's highlander,
its increased signal strength @ 30km from the transmitter when the antenna is isolated & choked,

i know w8ji said it needs radials, i will find out when i try it,

When it comes to the report you linked above, he only looks at peak gain, which is a measurement that is always angled up into the sky (aka take off angle). This isn't very useful for determining local signal strengths at a distance. However, when Henry released that report, posting on this forum he referred to something called surface wave, which is a different measure entirely. Essentially the surface wave data measures the signal strength as the signal travels along the earth, which is much more useful for simulating local contacts as it is a ground level measurement. This is why Shockwave was able to measure such a difference on real world antennas that didn't appear to show up in our models, what he was doing was apples and oranges to what we were looking at.

Here is an old Vector 4K model I did with 4 x 109" horizontal radials vs. no radials.

I see a significant disadvantage in adding radials, but I don't know if the differences would be noticable on the air. The currents noted on these radials are very small in magnitude.

No attempt at matching was done on these models, but you will notice the match is not bad considering my placement of the (feed point) source.

Maybe it is the matching system that I have added, but my results differ.

Both of these have an AGT of 1, are set the same height above the earth, are over the same earth, ect. The original model I used was created by ghz24, then modified by me, and in this case was set to the dimensions that HomerBB got his best results with this antenna design. The only difference between these models are one has horizontal radials and the other does not. With this result, you won't notice a difference.

The same antennas, except looking at the surface wave data instead of gain. Measurement taken 20 miles from the antenna, and measures from 0 to 1 wavelength in height. The further the line is to the right the stronger the signal strength.

As we can see, their is very little difference here as well, the model of the antenna with no radials slightly ourperforms the model with radials, but here again, you won't notice the difference.

Here are the layouts with current strength being displayed.

As we can see, their are very few currents showing up on the horizontal radials. The basket area itself is doing the job that radials normally do, and is doing it rather well it seems. If enough currents were pulled from the basket area this would have a far more detrimental effect.

I am aware that Eddie is getting a different result than I am, even if I put the radials lower down like he did, and I have come up with two possibilities as to why.

1) My model includes a gamma match, which may or may not have an effect. In the past I have shown that adding in a matching network can change the current flow on the antenna to some extent, so it isn't beyond reason that we are seeing some difference because of this.
2) The dimensions of our models are likely at least a little bit different. My model, for example, is built based on HomerBB's dimensions. I do not know what dimensions Eddie used, but if he used the stock Vector dimensions, they are different. It is very likely that the dimensions I used as a starting point are simply more stable to this addition than the dimensions Eddie used.


The DB

 

[bob85]

DB
i see the same kind of improvement over 5/8waves mounted on the same pole as shockwave claimed,
gain models don't support what i have seen in my own tests.

do you know why Henry's models show a different result for signal with radials than your model, you have the same trend but nothing like as much difference,

have you had a look at the new vortex with 3/8wave radial sleeve.

 

[The DB]

DB
i see the same kind of improvement over 5/8waves mounted on the same pole as shockwave claimed,
gain models don't support what i have seen in my own tests.

That is correct. Think about it, how high above the earth is a signal at 10 or 15 degree angle of radiation (TOA) where peak gain is when you are talking to people 20 to 30 miles away? That number that everyone likes to cling to is completely irrelevant in such a situation.

do you know why Henry's models show a different result for signal with radials than your model, you have the same trend but nothing like as much difference,

Likely for the same reason Eddy's and my models showed different results. I am not sure of the exact dimensions of Henry's model. When moving where the horizontal radials were positioned on my antenna model, right at the level of the base of the basket had little effect. When I put them below the basket area, like Eddy's model shows I had more of a drop in gain. When I lowered them still further gain started going back up. I didn't lower them enough to see if said gain would go up on the antenna overall, so I will leave that as a possibility, but, at least on my model, their seems to be a worst case position to mount said radials a few inches below the basket area.

have you had a look at the new vortex with 3/8wave radial sleeve.

I have played with the basket radial size and angle many times. As I recall, making the basket radials longer, and the loop larger, would actually increase gain. It has been a while since I played with such models, and I definately haven't made such adjustments since I made a model with a built in gamma matching system.

Essentially, with this antenna model, I am able to "steer" the angle of an antenna's radiation in free space by making adjustments to the basket area dimensions of this antenna, and I found that steering the angle of maximum radiation in free space to the same angle as the antenna's take off angle when it is over an earth, I was able to adjust the antenna model to produce peak gain over said earth. For example, if over an earth the antenna has a TOA of 11 degrees, the closer the free space antenna model was to showing gain at 11 degrees over horizontal the more gain the same model would report when it was over an earth. As you passed that 11 degrees peak gain in free space gain would then start to drop in the model over earth.

This is the basis of why I think your (and Shockwave and HomerBB)'s antennas did not match with what the antenna models were showing. What would happen if instead of steering an antennas peak angle of radiation to where it will produce gain on said chart, you angled it towards the earth 20 to 30 miles away? Overall gain at the peak angle would go down, but the antenna would be more sensitive to the people who are 20 to 30 miles away.

Their are a few concepts that Henry mentioned on this forum that were not in that report you linked to above, and this was one of them. I think he wanted more people to play with this aspect as he provided the ghz24 model (that I later improved on) to show this capability. This was just one concept that he talked about that most people just breezed right over and seemed to ignore for some reason.

Is it possible that by using the 3/8 wavelength radials in the basket area they were able to create a similar effect? Sure. I don't know what they did with overall antenna length, if they adjusted it at all, or the basket ring size either. I would point out that if the basket radials are 3/8 wavelengths long, then the basket is electrically even longer than that, perhaps even approaching and electrical 1/2 wavelength long as the ring on the basket adds to said basket's electrical length.

Did we ever get the dimensions for said specific antenna?


The DB

 

[bob85]

DB
I don't have dimensions for the new vortex,
hopefully oggy will give Eddie the measurements, if not we will have to wait for somebody buying one,

I would have thought that you don't need exact dimensions to see if there's any truth in the gain claims,

there must be something in the extra bandwidth that they claim & oggy noted in his review, the regular version has nowhere near that bandwidth,

years ago when the sigma vs 5/8 debate started i claimed that i thought i was steering the takeoff angle by altering relative lengths of the radials and radiator,

im still not sure what was going on but signals from distant locals could be manipulated at this location and other friends locations,

whatever was happening it does not show up in gain models,
you may have just given me the answer,

my buddy up the road has the old style vortex Q82, today he wanted to swap it for my i-10k,
i have no use for any 5/8 groundplane but I don't need another vector style antenna.

 

[The DB]

I would have thought that you don't need exact dimensions to see if there's any truth in the gain claims,

If I use a basket of that length, I can compensate the antenna by adding length to the central radiator to bring gain up. However, when I then adjust the matching system, gain drops to slightly below the point I started from. We are talking a gain difference of 5.37 with the original model and a gain of 5.3 with the long basket model. As I am able to get close with just a quick adjustment, if I could change the size of the ring on the basket area and it wouldn't surprise me if it can get a slight increase in gain over the original. That being said, unless we are talking a large increase in ring diameter, which doesn't appear to be the case based on pictures of the vortex antenna, I don't see the difference being noticeable.

Another thing to note is I can't get the larger basket model to tune properly with the built in gamma match, so I cannot compare SWR bandwidths between the two designs. I simply can't get SWR to tune below 4:1.

years ago when the sigma vs 5/8 debate started i claimed that i thought i was steering the takeoff angle by altering relative lengths of the radials and radiator,

you may have just given me the answer,

Essentially, when it comes to RF steering, I guess I have brought you full circle then. You can't change the actual TOA, but I can show with modeling this antenna in free space that RF steering is possible, and in the case of total gain I can show that RF steering makes a difference. Your experimental data simply takes what my modeling shows in one direction and successfully applies it to another direction as well, in your case the horizon, or at least the area at the furthest edges of local range, or with Shockwave's tests, steering is pushed to an actual downward angle from the antenna itself to the receiving antennas below...

This explanation meets Occam's Razor, which rates it highly in my book.


The DB

 

[bob85]

maybe when we get the measurements of the long cone version things will be clearer DB,

i take what antenna makers claim with a pinch of salt until its proven to be true,
Vortex made untrue claims about the first version of Q82 that my buddy owns & untrue claims about the mk1 Q64 that another buddy owns.

 

[JAF0]

Well I guess it's going up without radials but beefed up with old Avanti / Antenna Specialists Sigma 4 tubing in place of that diminutive 1/8" soft aluminum rod and top corona ball, though I might devise a way to save the corona ball.
I also found about 175' of squirrel proof Andrews LDF-50A hardline I've decided to use running the 108' up the fir tree and might even add a rotor and camera since the valley is right below me. Maybe if I look real hard I can see the RF energy bouncing off antennas below.

DB
I don't have dimensions for the new vortex,
hopefully oggy will give Eddie the measurements, if not we will have to wait for somebody buying one,

I would have thought that you don't need exact dimensions to see if there's any truth in the gain claims,

there must be something in the extra bandwidth that they claim & oggy noted in his review, the regular version has nowhere near that bandwidth,

years ago when the sigma vs 5/8 debate started i claimed that i thought i was steering the takeoff angle by altering relative lengths of the radials and radiator,

im still not sure what was going on but signals from distant locals could be manipulated at this location and other friends locations,

whatever was happening it does not show up in gain models,
you may have just given me the answer,

my buddy up the road has the old style vortex Q82, today he wanted to swap it for my i-10k,
i have no use for any 5/8 groundplane but I don't need another vector style antenna.

They show 415cm or 13' 7 3/8" for the basket height and 240cm or 94.5" for the ring length which is 30" diameter, and overall height of 834cm for 27.5mhz
or 27' 8 1/8" for 27.185mhz for the Vortex Q82 MkII

Seems like they should've tried the extended basket with the 7/8 wave length, makes more sense to me.

 

[br549]

interesting that they added 5 ft of length to the cone elements but kept the loop the same diameter and not much to the over all length . is vortex a new maker of the old sigma 4 style ?

 

[The DB]

They show 415cm or 13' 7 3/8" for the basket height and 240cm or 94.5" for the ring length which is 30" diameter, and overall height of 834cm for 27.5mhz
or 27' 8 1/8" for 27.185mhz for the vortex Q82.

Are you sure of those numbers?

Here is a comparison of the vortex dimensions vs the homerbb dimensions I used above.

These dimensions are far less efficient than the dimensions I got from HomerBB and it shows. I had to set up and tune that antenna with no mast, otherwise it simply would not tune, and its gain was way down. I think part of the reason for that are the currents that are present on the mast throwing everything off...

As we can see, the currents on the mast are pretty significant. The other Vector models I have do not have this problem with. Also, these currents make the model itself unstable, with rather large changes due to mast length. If using this antenna I highly recommend isolating the antenna from the mast if possible. Actually, this may be one that 1/4 wavelength horizontal radials actually benefits...

That being said, once the issues by the mast are taken into account, this antenna design does offer a wider SWR bandwidth than the other model I have been using.

So, it appears to be a less stable antenna with a bit less gain, but it has a much wider 2:1 SWR bandwidth... The efficiency for the model with HomerBB's dimensions has an efficiency of 66.56% and the Vortex model has an efficiency of 36.59%. I think that the much wider bandwidth they are reporting, and modeling duplicates, is caused by this antenna design's lack of efficiency, at least in part.

I want them to produce a great clone of this antenna, I really do, but this just isn't it...

Because of this antenna's lack of stability when it comes to different length masts, and the fact that it appears to be worse in every way that matters, I cannot recommend it. For a company that copies other good antennas to sell as their own, they didn't do that great of a job with this one, at least according to modeling...

Unless of course the numbers given to me, and which are also on the Vortex web site as well, are wrong...


The DB

 

[JAF0]

Are you sure of those numbers?

Here is a comparison of the vortex dimensions vs the homerbb dimensions I used above.

These dimensions are far less efficient than the dimensions I got from HomerBB and it shows. I had to set up and tune that antenna with no mast, otherwise it simply would not tune, and its gain was way down. I think part of the reason for that are the currents that are present on the mast throwing everything off...

As we can see, the currents on the mast are pretty significant. The other Vector models I have do not have this problem with. Also, these currents make the model itself unstable, with rather large changes due to mast length. If using this antenna I highly recommend isolating the antenna from the mast if possible. Actually, this may be one that 1/4 wavelength horizontal radials actually benefits...

That being said, once the issues by the mast are taken into account, this antenna design does offer a wider SWR bandwidth than the other model I have been using.

So, it appears to be a less stable antenna with a bit less gain, but it has a much wider 2:1 SWR bandwidth... The efficiency for the model with HomerBB's dimensions has an efficiency of 66.56% and the Vortex model has an efficiency of 36.59%. I think that the much wider bandwidth they are reporting, and modeling duplicates, is caused by this antenna design's lack of efficiency, at least in part.

I want them to produce a great clone of this antenna, I really do, but this just isn't it...

Because of this antenna's lack of stability when it comes to different length masts, and the fact that it appears to be worse in every way that matters, I cannot recommend it. For a company that copies other good antennas to sell as their own, they didn't do that great of a job with this one, at least according to modeling...

Unless of course the numbers given to me, and which are also on the Vortex web site as well, are wrong...


The DB

It appears it has almost the same energy at the low angle as Homer's but loses a lot in the upper angle regions. Definitely not as good for short skip but for a low angle performer only, it's very impressive with so wide a low swr range and less than half a db loss.
Did you try modelling it isolated from the mast and choked? Maybe for some unknown reason they posted the wrong specs. Maybe they are using the full 7/8 wave? Seems like it would make more sense to capture the bottom deconstructive 3/8 of current but allow the full 1/2 wave current above the basket on a 7/8 wave to radiate. if the basket is 3/8 then they're only getting 3/4 of the half wave of constructive current above the 13' basket on a mere 3/4 wave length antenna..

Also, would you mind sharing Homer's dimensions which you are working with?

 

[The DB]

It appears it has almost the same energy at the low angle as Homer's but loses a lot in the upper angle regions. Definitely not as good for short skip but for a low angle performer only, it's very impressive with so wide a low swr range and less than half a db loss.
Did you try modelling it isolated from the mast and choked? Maybe for some unknown reason they posted the wrong specs. Maybe they are using the full 7/8 wave? Seems like it would make more sense to capture the bottom deconstructive 3/8 of current but allow the full 1/2 wave current above the basket on a 7/8 wave to radiate. if the basket is 3/8 then they're only getting 3/4 of the half wave of constructive current above the 13' basket on a mere 3/4 wave length antenna..

Also, would you mind sharing Homer's dimensions which you are working with?

Except for the current data, all the rest has no mast or feed line attached, so isolated mast and choked would be an accurate description. I doubt that their numbers are to far off, when I look at their images of the Q82 it appears to be the same dimensions as my model.

Homer's dimensions? Antenna length, 336 inches, ring height 99 inches (note that is not the length of the radials that attach to the ring but the rings height above where the radials attach). Ring diameter is the same.


The DB

 

[JAF0]

Except for the current data, all the rest has no mast or feed line attached, so isolated mast and choked would be an accurate description. I doubt that their numbers are to far off, when I look at their images of the Q82 it appears to be the same dimensions as my model.

Homer's dimensions? Antenna length, 336 inches, ring height 99 inches (note that is not the length of the radials that attach to the ring but the rings height above where the radials attach). Ring diameter is the same.


The DB

Just for fun, have you tried a 7/8 wave with the 3/8 basket?
I laid awake last night for an hour with this thnig going through my head, trying to see it as a circle, or a full sine wave, and when I looked at the sirio that way it worked fine. 3/4 up and 1/4 in the basket gets a full 360 degrees, but a 7/8 with a 3/8 basket doesn't look right to me. I figure the voltage peaks at the tip and again a half wave length down where the ring would be to capture the bottom 3/8 but when the basket folds back up it seems the bottom 1/8 wave of basket would be constructive current but then it seems the 1/4 wave of basket above that would'nt be.
I really wonder what that monstrosity looks like when modelled.
And thank you for Homer's dimensions.

 

[The DB]

If you look up at post 18, that is 3/8 wavelength radials to the ring, and the central vertical element was tuned for peak gain. It is longer than 3/4 wavelengths in length, but that should give an idea of such an antenna's performance.


The DB