I-10K/Sockwave model first run

[The DB]

I was attempting to make a model of a .625 wavelength antenna that included a trombone style matching system as found on the I-10K and Shockwave antennas, and I succeeded, although it took me a while to get the model to tune properly.

The first image will show the layout and the current distribution of the antenna.

As we can see in this image we have a tapped trombone matching system. We also have two high current locations on the antenna, one is where we would expect it to be 1/4 wavelength down from the tip, and the other is in the matching system. This is to be expected on this type of antenna.

A note on the trombone matching system, there are a few limitations about using this system when it comes to modeling, I will discuss them below.

Next we see the radiation pattern.

The first thing to note here is, while close, the pattern is not the same on both sides, that is because the matching system is causing a slight skewing of the model. I would expect less skewing in the pattern of the actual antenna as the matching system as modeled I was unable to get to include the curve I mentioned above. There will still be some skew, but the skewing will be less, making the pattern more even than it is now.

Next we will look at the antenna data.

As we can see, the antenna tuned very well. With some playing I could get the tunign even better, but as it is, we are already better tuned than an SWR meter by itself would tune, we are also more accurate than most antenna analyzers will show, so I am happy with this.

The next thing to look at is the Efficiency and Rad-eff numbers. The Radiat-eff number is telling you how much of the total power going to the antenna is being radiated to the far field. The Efficiency number tells you how much of that power is being lost int eh antenna itself. In this case, all of that is from the antenna material I used, which is T6 Aluminum. 0.14% of the power is being lost to heat simply due to the material the antenna was made out of. This is also reflected in the Structure loss number in conjunction with the Input power number.

Next we see the SWR graph.

The middle half of these charts is the CB band. This should give an idea about bandwidth.

Also impedance (X and R).

And finally, for those who like smith charts, the range of frequencies in the above graphs as plotted on a smith chart. For those who are unfamiliar, everything within the black circle is under 2:1 SWR.

A few notes on this model.

1) The antenna's radials are about 1 wavelength above poor ground.

2) To get this antenna to where it could be tuned normally I had to use a smith chart to plot the frequency range used. Normally we tune antennas so X=0, but there was no X=0 point until I got the matching system close enough to a match. Once we got to a certain point, using X as a means for tuning wasn't a problem, but if you try and make such a model from scratch, you will likely have the same issue.

3a) One other note about this matching system that didn't come up. On the actual antennas, the bottom part of the trombone matching system is either in line with the radials, or immediately above them. Due to the limitations of the NEC2 engine, I was unable to put the matching system in line with said radials, or any lower above the radials. This is a limit that I have to live with working with the NEC2 engine.

3b) A side effect of 3a is if you look closely at the radials in the first image above, you will see that the currents on the two on the left are slightly stronger then the currents on the two on the right. This is due to the matching system layout, and if I were to get the matching system lower, like it is on the actual antennas, the difference in currents for the radials would be even larger. We could account for this to a point by making two of the radials slightly longer, but that is not how these antennas are sold.

4) While the antenna is made completely out of T6 aluminum, it is also entirely 6mm (about half an inch) in diameter. Parts of the actual antennas have different diameters. Because of this there will be a slight difference in various aspects of the antenna, but noting big.


The DB

 

[The DB]

I had some more time before I had to go today, so I modified the model to show the same antenna/matching system except the antenna is 0.64 wavelengths in length instead of 0.625 wavelengths in length. It is all very close, so I won't post most most of the results, little has changed from the data above. I will, however, show a radiation pattern comparison.

Here we see the .64 wavelength model (i10k-3.out) has slightly less gain than the .625 wavelength model. However, it has slightly more gain at higher angles. It isn't drastic, and you won't notice the difference, but for those that believe that a .64 wavelength antenna will always have more gain than a .625 wavelength antenna, there you go.

I don't have time right now, but I do want to see what length will end up having the most low angle gain...


The DB

 

[Marconi]

DB, I just recently found a printed copy of an old I-10K project modeling my idea of the trombone tuner. I think the link below is the thread where I posted the information, but the post bears no interest: http://www.worldwidedx.com/threads/marconis-eznec-model-of-jays-i-10k.179524/#post-508684

Attached below is a model of my I-10K that I recently did over using the wire details from the old model noted above. This model was on my old computer that recently broke. I had to do it over on the new computer. Then the new OS failed and I had to do a reset of the computer, and that process does not save the apps I added during setup. So, I looked for the hard copies and I saved the wires, so I won't have to rebuild it from scratch.

The difference I see is in a distinctive pattern and my match is not quite as good as your model. Note the pattern produces both vertical and horizontal RF and this is the first model where I noticed horizontal show up. I do have a switch in the main screen that allows one to select all, vertical, horizontal individually or in combinations.

I did fiddle with the model earlier and produced a versions "b", but that was lost in the OS failure. Before the computer broke I tuned the antenna and got a better match, but I have to redo the model and try tuning again.

The attached "a" model noted here includes a feed line, and I think that addition lowered the gain some, but I'll have to check that. This model also shows a very narrow <2.00:1 SWR bandwidth, and I recall an earlier tweak that produced a better match and remained close to 27.205 mhz. I will try and duplicate my results and get back with a better model hopefully.

Note: I don't recall testing this model to see how it performs setting it up in Free Space, but if it shows a good Average Gain, and does not show some deformed pattern, then maybe the model has some merit.

I see one error in the model below. I did not make the wire diameter the same as the coax when I added the feed line. I will fix that and I look for that to make some difference. I also notice that we look to have the source (Feed Point) on a different wire. I added my source to the center of wire #10 with 1 segment. I'm not sure if this small wire is OK with Eznec. My model also has the radials set symmetrical and the real I-10K has the radials set a little asymmetrical.

I also see that I made the radiator into three vertical wires of the same diameter, maybe .625" or .75". I know I fixed that earlier and that too make a bit of difference to the match. Eznec does not like tapper of any kind...me thinks.

Sometime back I also posted the I-10K model on Mauldroppers to the attention of Master Chief. He cast the idea aside like dirty underwear. At the time I was reporting that IMO the model was showing us what Jay and MC always claimed...the raised radiator and the trombone tuner allowed the I-10K to perform better that other 5/8 wave, and by a noticeable difference. I am not sure weather this model is and does what it shows for the real antenna, and your model doesn't support what I see in the pattern...so I'm not sure. I do know that the trombone tuner is big component compared to other matchers, and that might make a difference.

I will also have to compare my currents to what you report for the tuner as well. I seem to recall that my model showed the tuner as one polarity throughout, but I don't remember the sign (+ -).

I will send another model later of my I-10K without a matching device added, and maybe you can compare it to your similar model. In this model I placed the source at the base of the radiator at segment #1 like you might have done.

 

[The DB]

That match was a pain in the... well... you know... I'm glad I was able to get it done though, hell, that alone took me half a day to figure out. I think I have it figured out for the most part now so doing it again shouldn't be to bad.

I to have noticed the horizontal component in the radiated field. This isn't the first model I made that has both components, and I attribute most of it to the trombone style matching section, and a small part if it to the small current mismatch in the radials. I made a linear loaded 5/8 wavelength antenna about a week ago that uses a horizontal linear loading section that also had this effect.

When it comes to the feed point, I did mine a little different. I definitely did not simply put it at the base of the vertical radiator, that would defeat the purpose, and possibly make the antenna nearly impossible to tune within the modeling software. Instead I connected mine across the matching section, essentially, one side of the feed point is directly attached to the radials, in this case with a one segment wire, while the other side is tapped into the middle part of the trombone section. The matching wire like yours is one segment long, but is also connected different. I got it as close as I could to the pictures I saw which clearly had a tapped trombone section.

My radials are also symmetrical, I was unaware that there was a difference in the actual I-10K antenna's radials to begin with... I can understand the need for such a difference, although at the same time it isn't at a point that will make a huge difference.

I have yet to do any cmc testing with the model, that will come. This antenna has a full set of radials, do I don't see common mode currents being that big a deal. I have another project to play with first, and that is seeing what length, once tuned for, will the antenna produce maximum gain. Another model that used linear loading instead of a trapped trombone section produced maximum tuned gain with its tip .58 wavelengths above the radials. This was a surprise to me. It was a very similar design to the I-10K, just the matching system was a bit different.

I really want to make a Maco model as well, but I haven't figured out how to account for the capacitor hidden in its design... If anyone has the capacitance of that part I would need it to make such a model and tune it properly...


The DB

 

[Marconi]

When it comes to the feed point, I did mine a little different. I definitely did not simply put it at the base of the vertical radiator, that would defeat the purpose,

I had the thought; that if the feed point was made the source at the base of the radiator...then it would seem to me to just by-pass the trombone tuner. When I place the source at the base of the radiator I think I saw a better match than some tap points on the trombone, and you're right...the tuner had no effect when the source is not tapped to the trombone.

I used a split "Type" feature in Eznec...which allows the tap to get closer to a wires junction. Maybe your idea and this feature are similar. I don't understand the technical aspects of this part of modeling.

and possibly make the antenna nearly impossible to tune within the modeling software.

As noted above, this was my experience also...the antenna tuner had no effect on the tune with the source connected at the base of the radiator.

My radials are also symmetrical, I was unaware that there was a difference in the actual I-10K antenna's radials to begin with... I can understand the need for such a difference, although at the same time it isn't at a point that will make a huge difference.

The radials on Jay's antenna attach to the side of the tubular mount. There is another similar model out there in the market that does have the radials symmetrical.

I have yet to do any cmc testing with the model, that will come. This antenna has a full set of radials, do I don't see common mode currents being that big a deal.

My model has currents turned on and I see very little current flow on the antenna view image, and the tabular currents data shows very little currents too. I'm of the opinion this all indicates the ideas when CMC manifest or not, but that is just a guess.

Another model that used linear loading instead of a trapped trombone section produced maximum tuned gain with its tip .58 wavelengths above the radials. This was a surprise to me. It was a very similar design to the I-10K, just the matching system was a bit different.

.58wl is pretty short, but I have an idea why this happens. I suspect that a model that shows the worst match that the model likely will show a little increased gain compared to another similar model that has less impedance transformation requirements at the feed point.

However, when I test the idea by skewing the antenna construction a bit to make the match worse...it will change the match, but the performance results often stays the same or makes only a really small difference.

I really want to make a Maco model as well, but I haven't figured out how to account for the capacitor hidden in its design... If anyone has the capacitance of that part I would need it to make such a model and tune it properly...

Just a few days ago I made a V58 model for Needle Bender regarding his issue on the forum about 5/8 waves, the Maco V58, and his idea about .64 wave, and I posted the results. I did not see any added benefit to the Maco, but I hear reports that it is a really good working antenna.

After I did that project...I was curious about adding the matcher to the V58 and I was pondering the same thing as you...where is the physical bottom of the antenna, how far up is the tap point on the radiator, and how do I account for the area that allows the up and down adjustment of the radiator that adjust the reactance...as you say the capacitance area. I'm still stumped or else I have a mental block on this one.

I'm also not sure how the different mix of tubing and flat bar stock in the feed point area will effect results. I have a feeling, working with the trombone, every little material detail makes a detectable difference for the model.

IMO the hubs on CB antennas we use likely have more important effects than I imagined in the beginning of my modeling. I think all the little parts around a feed point with high currents flowing...can make very sensitive responses.

 

[M0GVZ]

What I find funny about all of these different antenna designs is how they all try to re-invent the wheel but when you look at the elevation patterns they're all basically identical to each other give or take fractions of a dB which is kind of what you'd expect given that for all that extra metal that's supposed to make them work better than X or Y antenna they're still a 1/2, 5/8 wave etc monopole vertical.

Any differences when it comes to verticals are effectively undetectable in real world use and you're as well just saving your money and buying the best constructed antenna you can rather than the one with the most bits hanging off it making performance promises that only have validity in the marketing department.

Hell you may as well just go for a simple quarter wave groundplane antenna because at the lowest take off angles the difference is a couple of dB at best but for short range DX contacts within a few hundred miles the quarter wave is likely to do better. You don't need to worry about the wind, water getting in joints etc because you can make the vertical section out of a single piece of aluminium.

 

[222DBFL]

Can we get a plot for the Sirio vector 4000 The DB? Or is it just about the same as the others shown? I am just curious and if it's the same then no need to mess about with it. But it would be nice to see what it looks like. Thanks for any and all responses. Much appreciated!!!

 

[222DBFL]

And just to add, mine is not side mounted to the mast pipe but rather slid over it and centered. Also my height AGL, is 27ft to the base. It sure what if any difference this makes, but just thought I would add as much info about mine as possible. Also coax is completely isolated from mast with 1/2" rubber grommets made for LMR400 and i also have ferrite chokes at the feedpoint and the mast is grounded with #2awg solid wire from the base of the antenna all the way to the ground. Again, just trying to give as much info as possible. Not that it makes any difference, but that I don't know. Again, thx for any and all responses. I understand smith charts as well as I did use an anritsu s331e for many years for sweeping coax and trouble shooting of coax and antennas as well for cell sites. Not that that makes any difference either. But again. Just trying to give as much info as possible. Again, thx for any reponse and have a great day!!!

 

[The DB]

I used a split "Type" feature in Eznec...which allows the tap to get closer to a wires junction. Maybe your idea and this feature are similar. I don't understand the technical aspects of this part of modeling.

I simply put one side of the feed point where the shield would connect, and the other where the center conductor connects. That is how I always thought said connections should be connected.

What I find funny about all of these different antenna designs is how they all try to re-invent the wheel but when you look at the elevation patterns they're all basically identical to each other give or take fractions of a dB which is kind of what you'd expect given that for all that extra metal that's supposed to make them work better than X or Y antenna they're still a 1/2, 5/8 wave etc monopole vertical.

Any differences when it comes to verticals are effectively undetectable in real world use and you're as well just saving your money and buying the best constructed antenna you can rather than the one with the most bits hanging off it making performance promises that only have validity in the marketing department.

Hell you may as well just go for a simple quarter wave ground plane antenna because at the lowest take off angles the difference is a couple of dB at best but for short range DX contacts within a few hundred miles the quarter wave is likely to do better. You don't need to worry about the wind, water getting in joints etc because you can make the vertical section out of a single piece of aluminium.

When it comes to overall performance differences between antennas, most of this is something that both Eddie and I have both stated multiple times, and we both agree that the difference is even less when mounted at the same tip height. That being said, sometimes I find parts of a model that shows me something that I didn't already know, or that seemed to work differently than expected. The early part of matching the above antenna design for example. Just because we know that in general these antennas all seem to perform about the same, that doesn't mean that their isn't more to learn by making these models. I think the effort is still valid.

Can we get a plot for the Sirio vector 4000 The DB? Or is it just about the same as the others shown? I am just curious and if it's the same then no need to mess about with it. But it would be nice to see what it looks like. Thanks for any and all responses. Much appreciated!!!

This might be more difficult that you think. I don't have any Vector 4000 models that includes a full and functional matching network, and while the pattern shouldn't be affected significantly by such a device, putting such a direct comparison up wouldn't be fair, and some people would see it as such and read more into it than they should. If you just want a basic pattern, I am happy to go back and find one, possibly the one based on HomerBB's dimensions to the antenna he states is the best performing vertical antenna he has ever made. I would have to dig it up however. If I find it I will post it, just don't try and use it as a direct comparison between these antennas.

If you can wait until I get around to it, at some point I intend to make a Vector 4000 model including full gamma matching. It is on my list of things I want to do. I am curious as to how it will compare to a raw model with no matching included in several specific ways. There are differences in how certain things work on a stock model with no matching and what Shockwave (who used to post here) has told me happens on his actual test antennas, one of them happens to be the effects of the diameter of the ring and its effects on gain, my models show max gain at much wider ring diameters than his live test antennas...

I know most people see these antennas a certain way, and that is fine, but there are details about this antenna design that no one has addressed, and I find fascinating. I think there is still more going on with this antenna than many people realize...


The DB

 

[222DBFL]

No hurry at all!! I was just curious is all. Didn't realize that it was so different of an antenna then the others. I have one and will say it does perform quite well for a vertical antenna. And again, thx for the response!! Will wait as long as needed. God willing I won't be going anywhere anytime soon!! Thx DB!!

 

[bob85]

DB
When shockwave made the large ring version he also made the radials significantly shorter, he posted that it did not work so well,

avanti claimed a small increase in gain with wider flared radials up to 30 degrees,
I'm pretty sure they did not mean shorter radials,

 

[Marconi]

I simply put one side of the feed point where the shield would connect, and the other where the center conductor connects. That is how I always thought said connections should be connected.

With Eznec the source is placed on the antenna by indicating the wire and segment number in the Source Data window. The feed point then shows up on the Antenna View as a O red circle at the point you assigned. I do not understand the technical aspects for how that happens in Eznec however.

I redid my I-10K model on my new PC. I checked the dimensions against the Manual and I find the radiator length is possibly an inch or so short, but I didn't mess with it. The tune was just like I posted earlier with only a fair match. It was close, but I tuned the model anyway, and it goes just like we would the do with a real antenna...I adjusted T1 and T2 and made sure the radials were set right too.

The best SWR I was able to get is 1.5 SWR.

I did the model over Average Earth soil. The first image in the attached PDF file is the main screen and shows this setting under Ground Description among the others.

I checked the trombone currents, but my model does not show a difference in polarity from side to side...like you noted. I also noted that the magnitude of the currents on the trombone matcher are very strong. IMO this may be why the model shows the horizontal responses it does.

I also set the pattern to show horizontal, vertical, and total field values. The pattern for the vertical part is pretty similar to your model. I don't show as much gain as you do however, but I think your model was over very lossy Earth and that would shows us better gain I think.

I added a mast to my model so I could see the currents flowing on the feed line, but I did not add a feed line to the model. The currents on my tabular currents report show to be very low considering I used a the 32' foot feed line = to the length of the mast I used.

I also made a model in Free Space so I could check the Average Gain results, and that is posted as a separate model. It shows to be a very good low value.

 

[Marconi]

DB
When shockwave made the large ring version he also made the radials significantly shorter, he posted that it did not work so well,

avanti claimed a small increase in gain with wider flared radials up to 30 degrees, I'm pretty sure they did not mean shorter radials,

Bob here is as thread talking a little about the large ring deal Shockwave did. I didn't get dimensions from him, but I made a model in Eznec. It is in my old computer so I can't be for sure...but I think my model showed the wider loop performance was no way no.

Avanti Sigma4: An alternative view point

 

[222DBFL]

Thx for the link Marconi, very good read!!! Here's to hoping you are feeling better and get well soon!! And also thx to the the DB as well for responding to my post! I am much appreciative of all the help!! Good day to all and have a good one.

 

[The DB]

When shockwave made the large ring version he also made the radials significantly shorter, he posted that it did not work so well,

That might be what he was referring to. I don't know the angle that I ended up with so I don't know if what I have seen might be the same thing the patent is referring to or not.

Bob here is as thread talking a little about the large ring deal Shockwave did. I didn't get dimensions from him, but I made a model in Eznec. It is in my old computer so I can't be for sure...but I think my model showed the wider loop performance was no way no.

For the record, I am well aware of your linked thread, including this part of it... I was referring to something that was discussed in a private conversation between Shockwave and myself that went beyond that part of the linked conversation.

If I make a big loop Vector model, I can get more gain out of the antenna than the stock dimensions, but it takes more than just making the loop bigger. You have to balance the antennas overall length, and the radial length as well. If your not willing to adjust all three you won't get anywhere.

All this being said, I didn't create this thread to discuss the Vector again. It is a dead subject, and should stay there. Even if I find certain aspects of that antenna interesting, which I do, I have resolved to study them on my own simply because some people treat even questions about various aspects of that antenna as a threat to what they intend to believe with religious like zeal.

The only open discussions I intend to ever have about this antenna is after I make a model that includes tuning with what is as close as I can get to the Vector's matching system and possibly how it compares to other models with their tuning systems modeled and matched as well. I have yet to see any Vector model include a gamma matching system, much less a fully tuned version in a model. Hell, I haven't seen many models of other antennas that have been matched and/or tuned either.


The DB