Is the Solarcon Max2000 5/8th di-pole like ?

[RadioDaze2.0]

My own personal experience with coaxial chokes and ferite chokes is that it effect the SWR negatively using an IMAX2000.

I popped a MJF 1:1 balun inline and that caused the SWR to jump to 2.5:1 I wondered of it seemed to interact negatively with the matching arrangement.

Similar situation with a coil of coax as per the chart above.

Just does not seem to work in my installs which can vary from place to place as I change QTH and mounts.

 

[The DB]

DB, I took a shot at duplicating your model using Eznec, and I think I got close. I made one just like your model with without a mast to the ground. I added an ISO mast to the ground to the other.

I also added an X where my wires are ISO, not connected.

Your isolation (ISO) fix does look to minimize the CMC's on the mast of your model better than my "Imax no radial 32' mast ISO" model.

But, in my PDF file below you will see that my model does not raise the maximum TOA up high like your model does. See the pattern overlay I added for comparison.

In these models, I also can't blame the differences in the patterns we see due to the very high SWR mismatches in my Imax models. These three models all show nearly the same mismatch.

I posted exactly one model that had a higher angle of radiation without radials than with, and that model has nothing to do with your Imax at 32 feet model, they are nothing alike. The model in question was a request by you... Lets backtrack...

I posted this:

Seriously? Ok, how about this one, a 5/8 wavelegnth, with no radials, and a single 1/4 wavelength section below the antenna simulating putting a choke 1/4 wavelength down the coax from the antenna. The mast is isolated...

The top half wavelength is a given phase. The remaining part of the 5/8 wavelength element is out of phase, as expected. As you pass the feed point onto the lower element, the phase does not change, thus the area immediately below the feed point on a vertical 5/8 wavelength antenna, will always be out of phase with the upper part of the antenna no matter how long that feed line/mast are. The best you can do is to manipulate the length of said wire to put a phase change right next to the feed point of the antenna.

So, I have a model with a 5/8 wavelength above the feed point and 1/4 wavelength below the feed point and no earth connection as the antenna was mounted about 20 feet off the ground. Very different than your 5/8 wavelength above the feed point and mast that goes 32 feet blow your feed point and connects to earth model. That is the only plot comparison I posted in this thread that, with and without the radials, showed a different angles of maximum radiation between models. It also has no relation to any full length mast model out there as it was not made for or part of that discussion. Strangely, it was you that wanted to see the results of that model with and without radials, so I added radials and showed the results.

Can you show us what happens with the gain on the model you posted above, before and after you add the choke?

The model in question was created and intended to show what putting a choke 1/4 wavelength down a feed line would do in comparison to choking at the feed point of said antenna. By your initial response it appeared that you understood this, however, you seem to have forgotten that this model had to do with an entirely different line of discussion that was taking place in this thread simultaneously.

Why don't you look at the results from the two different models radials vs no radials models I posted at two different heights, both of which had a mast that went all the way to the earth below just like your model. Their results are much closer to your results, the same radiation angle and everything. The one big difference is the larger amount of change when it comes to gain, my models show less gain for the no radials models than yours. There is a logical reason for this difference, and as a matter of fact making one change to one of my models will come very close to the results you have. I'll let you figure that difference out on your own.

And finally a question. Are you prepared to say that based on so few models that no matter the circumstances of an Imax install, that adding horizontal radials will never change the angle of radiation? If dealing with masts with a ground connection like you are using, that would be an awfully bold claim based on so little evidence, although possibly true. You would need to do far more testing than I have seen from you on this topic to confirm it, and even more tests if you wanted to try and confirm the same thing with angled radials as well. I would be very interested in the details of such a study...


The DB

 

[M0GVZ]

My own personal experience with coaxial chokes and ferite chokes is that it effect the SWR negatively using an IMAX2000.

I had mine mounted on a 21ft pole. Using a ferrite choke made no difference to the SWR. Most likely the pole was the deciding factor in this.

 

[Heavy Metal]

HM, other than the choke helping solve your interference issue with your speakers...can you tell if there is any advantage in how your Imax performs?

What is the tube looking object a few inches to the side of the mast?

Really seen nothing different and now running power still no difference other than not comming over things. Signal report wise by same few talk too, and ears still same levels. Basically I wondered if it even did anything other than the things before it bleed over on stopped and I'm only up @21' on fence rails as antenna poles.

 

[Marconi]

Really seen nothing different and now running power still no difference other than not comming over things. Signal report wise by same few talk too, and ears still same levels. Basically I wondered if it even did anything other than the things before it bleed over on stopped and I'm only up @21' on fence rails as antenna poles.

Thanks HM. I think we see about the same results, and you did good if you were able to eliminate the interference on you speakers, etc., using a choke.

 

[Marconi]

I posted exactly one model that had a higher angle of radiation without radials than with, and that model has nothing to do with your Imax at 32 feet model, they are nothing alike. The model in question was a request by you... Lets backtrack...

DB, to me your model of a CMC fix was just another possible solution among the several that I posted above.

The only point I was trying to make in comparing your CMC solution to mine on a Imax with no radials...was the difference we see in the pattern results.

Bob originally raised the point early in this thread that CMC produce bad patterns and I've been trying to support that point with my Eznec models in my posts #33 and #49. I can't be sure, but I also think Bob might suggest a similar solution for an isolation type fix on the Imax...similar to what you did in your model, even though he would likely say we also need to add radials.

So, I took the idea and duplicated your Imax with no radials using Eznec, to see how it compared to my CMC solutions for and Imax with no radials like I posted earlier.

I actually did one model like I think you suggested, with a single ISO 1/4 wave mast below the feed point and not connected to Earth. Then I simply added another isolated mast to Earth...as another model. Both models were posted and described, and it turns out they were very similar in results. Did you overlook that?

To be fair though, I did have to guess at the dimensions...so I just used my dimensions.

I realize you posted you model to prove your point about the phase of the currents on the mast, and I agreed with you on that point.

Again, I wanted to see what such a model's pattern looked like, and how it's performance results compared to the other models I had done earlier.

 

[Marconi]

That is the only plot comparison I posted in this thread that, with and without the radials, showed a different angles of maximum radiation between models.

DB, I've been looking over your earlier responses, and as I come to questions I will try and post more. Sorry I'm behind in posting. Some days are not so good for me.

I realize you have posted other model results. Sorry, but at my age I just haven't gotten around to those yet, I missed em', or I forget em' some times.

 

[Heavy Metal]

Thanks HM. I think we see about the same results, and you did good if you were able to eliminate the interference on you speakers, etc., using a choke.

Thanks!!!!


Not a prob, interference was awful too and really bad on some things too.

This was just to see if these things worked before spending and arm and leg to figure out. And what did you know they do work I just looked at chart and went by frequency range I was at and wanted to suppress with max range which I saw >4K - >5K range and that higher is better so, it works just now when go wider need to look above and spend a few dollars to achive.

 

[Marconi]

Take these models for example...

The DB[/QUOTE]

DB, I tried to duplicate your models above at 24' feet. I had to guess at the dimensions and my model is at 27.205 mhz. I had to find by testing the Ground Description you might have used, I don't have a selection for moderate.

I was able to nearly duplicate both cmctest1 and cmctest1c to the same pattern and gain results as your models show above.

But when I removed the radials from model cmctest1c to try and duplicate your model cmctest1b, the model feel apart and produced the terrible pattern and gain as noted in the attached PDF file below.

In your descriptions you tell me that the cmctest1c (the blue lines) are the same as the "b" model except it include radials.

I cannot find a problem with this simple Imax with a mast attached to the Earth and no radials...that might explain this difference in results with your model "B".

The other two models I tried to duplicate came out almost identical in gain and pattern to your results.

Can you tell me how many segments you used for your wires, and the wire diameters used?

Also I'm using a ground description that is noted as "Very Poor" with details that read the following in order to get close to your numbers.
Conduction=0.001 S/m
Diel Const=5

Can you give me the details for the soil you used.

I wasn't expecting this development at all.

 

[The DB]

EZNec doesn't have a "Moderate Ground" option? That is news to me... I use that instead of "Average Ground" because it is actually closer to an average between "Poor" and "Good" grounds. Moderate ground has a conductivity of .003, and a dielectric constant of 4. If you can manually enter the numbers, that will match my moderate ground. I also don't have a "Very Poor" option. I guess that is just a difference between the software programs.

The cmctest1 series models were at 6 meters high, which should be near 19.5 feet or so. The cmctest2 series models were at 11 meters which is very close to 36 feet high. I use auto segmentation, 100 segments per wavelength, so there would be near 64 for the antenna, and 25 on the radials for the models that have them. Diameter is .001 meters, that is very close to 18 AWG wire. If I increased the diameter to .002 that would be near 12 AWG wire diameter.

I modeled said antenna at 24 feet as you have done, and strangely, even with no radials, my results are very different than yours. There are very few currents on the mast when I model the antenna at that height. As a matter of fact, at 24 feet in height there is virtually no difference in gain between having radials and not having radials...

And the currents for my Imax at 24 feet...

I checked AGT, and it is fine. Strange that our models show that much of a difference at this height. Most others tend to be pretty consistent...


The DB

 

[The DB]

For those interested, a while back I did an experiment that was related to a part of this discussion. I may have to do some digging if anyone has questions, but I will post the details/results of the experiment here.

I started with two 5/8 wavelength antenna models (not an Imax model, but a bit shorter). These models consisted of an upper 5/8 wavelength section, a lower mast section that went all the way to the earth below, and one of them had radials while the other did not. I modeled the antennas at 128 different heights between just above ground level up to 11 meters, all of the heights were spread equally apart (by about 3.4 inches). This was also over moderate ground... I recorded various data into an Excel document to plot the differences over the varying heights.

I'll let you guys draw your own conclusion from said data...

One thing that struck me when I did this was how stable one set of models was over the change in heights, compared to how volatile the other set of models were. A set of horizontal radials really does stabilize many aspects of a 5/8 wavelength antenna system...

Anyway, lets start with gain, because everyone and their brother loves talking about gain...

And, with gain people will inevitably talk about "Take Off Angles", so lets do that next.

Its worth noting here that for the antenna with no radials, two points here a higher angle lobe formed, and then became dominant. The first time it happened, the existing lower angle lobe got smaller and smaller until it disappeared, and the higher angled lobe got lower and lower and eventually matched the angle of radiation that the radials model had. Then another high angle lobe formed, took dominance again, although the process didn't actually repeat itself. In this case, the higher angled lobe got lower with height, and actually came close to merging with the existing lower angle lobe. As they got close together, the low angle lobe regained dominance.

To round up the performance part of these lets do radiation efficiency next...

Onto tuning data... Lets start with the R variable over the range of said frequencies...

And X comes next...

And finally SWR (before any form of matching would be applied to said models).

If you love analyzing things like I do, eat your heart out...


The DB

 

[Needle Bender]

Needle Bender here is a model of my Imax with slanted down radials at 67* degrees.

Hi Eddie,

I've been down with another nasty cold/flu for a week or so and I have no brain tonight so I'm not going to even TRY to read & digest these new pages, except to say Thank you and I apologize, I made you think I had my Imax at 32' but the guy wire is attached to the roof 32' down from the point on the mast where it's attached. The Imax is actually 41' at the top of the mounting plate. those guy lines attach to the roof, that's why they're 9' higher than the ground and only 32' down from a 41' high above ground guy point.

All I know is the damn thing works better in that config than any other I've tried, including full isolation and a current choke in the coax.

On a similar note, I recently installed a Penetrator at 33' with full isolation.

Two feet of 1" diameter solid fiberglass rod (with gray PVC around it for the right sizing to the U-bolts) and a current choke in the coax 6" below the P500 connector and ZERO ground, but now, finally, he has ZERO RFI in his house, computer speakers, Guitar amp, TVs, etc. Works great and has a 'little'
stronger signal all the way around here, on all the local meters.

OK, out for an Alka-seltzer break.
73

 

[Marconi]

Thanks DB, I will try and fix these models according to your tips.

BTW, I also found that when I raised the cmctest1b model back up to 32' feet it made a pattern similar to my original model at 32' feet, and that does not seem right.

I used really small wires too. I think the differences in wire size and soil type went a long way in making the differences my model shows, but that is just a guess at this point. I finally used the Ground Description to tune in on your results.

I did not check the AGT, but no errors popped up on my models either. I will check for segment and geometry errors, and see if I missed something.

Thanks for the details.

 

[Marconi]

Thanks for the update NB'r.

 

[RadioDaze2.0]

I had mine mounted on a 21ft pole. Using a ferrite choke made no difference to the SWR. Most likely the pole was the deciding factor in this.

It is an understandable assumption but I am fairly sure I have used various mast heights and thought I will use the MJF ferite isolator as the common knowledge would be that it is the done thing to use one or a coaxial choke to avoid any CMC, belt and braces approach. I always tried to offset the choke from the pole so it is not too close to the pole avoiding changing its qualities. I use a releasable cable tie to make the coax and choke bend away from the pole a bit.

In each case the IMAX become unusable (2:1 - 2.5:1) at various mast heights. Since I gave up on all chokes the SWR has been much better at all heights.

I suspect if I cut a few inches off it may improve further at my frequency of operation. (I could try the rings but they have had little effect thus far which I also find a little odd) The manual suggests:

Cut off :

8 inches for 28.016

9 inches for 28.106

10 inches for 28.267

So for 27.555 I suspect cutting 3 inches might bring that to a 1.2:1 SWR for me given it says it is tuned for 27.205 from the factory. I may well try that at some point. I would take off 1.5 inches at a time and check.