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

[RadioDaze2.0]

I would love nothing more than to add 1/4 wave DIY radials to an IMAX2000 and enjoy the performance benefits. But that is just impossible for me mobile static. Impractical to setup and take down in terms of time taken and also in terms of keeping them horizontal and symmetrical.

We all have our operational limits.

 

[RadioDaze2.0]

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

When I look at this it suggests that a no radial 5/8 wave should have most gain at 8.3M mast height which is interesting. (although if the X axis is still height above ground for the TOA graph at 8.3M approx that is very alarming suggesting much energy is way up into high angles 46 degrees or so) It also suggests that a Gain Master type antenna seems to take a lot of the negative and cantankerous aspects away from a no radial 5/8 wave. Though in practice thus far at least on line of sight contacts they seem to do as well as each other.

I just cannot seem to experience the predictions of many graphs and plots in practice between an IMAX2000 and a Gain Master. At least not for line of sight. Maybe an IMAX with no radials on a pole would never have made a contact to New Zealand I made long path 13,700 miles if that contact relied on a nice low angle cut into the F2 layer close to the horizon.

I wish I could correlate these predictions against my experiences. It just seems the disconnect between predictions and reality (or at least operational real world DXing) are not possible to prove without 2 antennas set up identically height wise (20M distant from each other to be sure) and a switcher.

I am surprised also at the differences in your plots in take offs from your no coax/no mast plots vs one with mast connected to ground. (even though a no coax/no mast antenna system is not a real world set up)

Interesting but I never get beyond that as it is very difficult to prove/sum up/correlate to a typical days DX set up that I would use.

I can only really make comparison between IMAX2000 and a Gain Master on long distance line of sight contacts and to all intents and purposes they seem to do similarly from day to day. (even though there can be the variables of tropospheric enhancements etc.) But averaging experiences out suggests they seem similar despite suggestion that much energy may be going out at 46 degrees with the IMAX2000 (the predictions being very similar in height and mast as I had it set up last weekend 9M aluminium pole, no radials)

Maybe for line of sight contacts TOA is not particularly meaningful. Which I would find strange from a theoretical point of view as you would think energy beams closer to the ground (of course still cutting above hills buildings and obstructions at an angle) would mean better signals to RX stations and better reciprocal receive signals at my end.

 

[Marconi]

RD, in my experience with CB vertical antennas at any particular height, as long as both current maximums are close to an equal height, all of my CB vertical antennas tend to be pretty similar in performance. I think this also applies to my experiences with the no radial Imax.

I am right now questioning my own ideas about CMC's however. When DB changed the heights of his models different than mine in this thread...it revealed more of a difference than I expected, and aside from some stupid errors I might have made trying to duplicate his models, it looks like Bob's predictions that CMC's on the mast/feedline does matter, and smacks of truth to me.

That said however, like you may be seeing in operations...I have never noticed a big difference and for years a difference is what my quest has been all about.

Bob's word on CMC does seem to make reasonable and good sense, but I doubted it, because I have never experienced a noticeable difference in my real world comparisons, and I use to do comparisons a lot. The only difference I can see is my real Imax antenna had a tuner that produced a nice match.

DB, I have worked with my models some more and I don't find but one thing I think really effects my attempt at duplicating of your models...and that is the differences in height.

I still am not able to duplicate your cmctest1b pattern noted in red on you post #40...no matter what I do.

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...

I don't know who most others are, but are you in-question here as much as I am?

 

[RadioDaze2.0]

You would think seeing graphs alone (and I respect the time that must have taken to prepare them The DB) the multiple parameters which are changing vs height for a no radial 5/8 wave antenna that you would have to be immensely lucky to get it to work anywhere near as well as Gain Master does which does not suffer from these mass variables. (as does a 5/8 with 1/4 wave horizontal ground planes)

But in practice I cannot realize the differences.

Unless as mentioned TOA is not as relevant as we think it is for close to earth contact i.e. line of sight comms. Whereas maybe (and it is a big maybe) for very long DX that relies on a very low angle cut in (beam) on the horizon it might mean the difference between hearing a very distant station and hearing none at all.

This is a stretch though because I can recall using a Gain Master to speak to someone in Australia with another station in the UK 150 miles away (a bit of team DX) also talking to them and they were using an IMAX2000 - albeit at reduced signal level to myself in part born of power differences. (no radials but on top of a sheet steel van roof, a ground plane of sorts) Now I begin to wonder if that IMAX2000 was on a few poles away from the van if there would have been a no contact. It is hard to believe though. Both myself and the IMAX station in the UK were operating hilltop which might reduce the differences seen in the graph as the slope off away from our antenna systems would also affect the TOA's.

The graphs seem to show potentially big differences in parameters where the practicality of operation seems not to present as big differences in practice on DX or line of sight.

I am not sure given different operating conditions and ground type that it is ever possible to accurately predict how one station would perform relative to the next from graphs alone. You might be able to get some reference point of course based on theory which is useful/important even. In this case above IMAX2000 on van roof vs Gain Master on 7.5M poles at somewhat similar heights, the IMAX station I know seems to operate around 270M ASL and I am typically lower down150M-200M. Maybe what is lost on the IMAX (if anything? given it has a ground plane of sorts/the van roof) is gained from the additional height ASL.

 

[The DB]

Unless as mentioned TOA is not as relevant as we think it is for close to earth contact i.e. line of sight comms. Whereas maybe (and it is a big maybe) for very long DX that relies on a very low angle cut in (beam) on the horizon it might mean the difference between hearing a very distant station and hearing none at all.

I must also point out, that take off angle, when it shifts up like it does, the low angle lobe doesn't just disappear. It was still there after the shift, but as it wasn't the dominant lobe I didn't record it on the chart. Also, I did point out that that was not an Imax model directly as it was shorter than an imax antenna.

Also, what is this we? I used to think that way, but haven't in quite some time. When I measure for local contacts I use a surface wave measurement, not a far field gain measurement. Even if you have a 5 degree angle of maximum radiation, how high is that going to be above the head of the guy you mentioned that is 150 miles away? The signal at that angle would be about 13 miles above the other stations's head, and that is assuming the earth is flat, as it is round, it would be even higher than that. Tell me, how would a maximum signal strength that is 13 plus miles above a guys head have anything to do with him on a local contact?

I've seen some people try and reference the same chart except point to a lower angle, such as signal strength at 1 degree, but even in this case, with your 150 mile contact example, that signal strength is still over 2.5 miles above the guys head, and again that is not factoring in the curvature of the earth.

Such a gain chart is wholly inadequate for determining local contact information of any kind, period. With another antenna in another thread, I demonstrated how a less than 3 dB difference in maximum gain comparison turned out to be over 6 dB at difference when doing the surface wave measurement at a distance. I also pointed out some observations from said experiment, namely the further away the transmitting and receiving stations are the larger the difference measured in gain would appear to be, and that near 6 dB measurement was no where near 150 miles out... With a standard far field gain chart you simply don't see this effect.

I'm not sure if the Gainmaster suffers from the same or similar variables or not. At the time I made those charts I haven't duplicated the Gainmasters SWR curve as of yet. That is something that I have since accomplished, and one day I might add such an antenna model's data to that data just to see what happens. I think that if there are any anomalies with the Gainmaster they will happen closer to the earth. That is something for another day however...

Also, be careful of treating any gain chart or graphs as I pointed to above as absolute. I never said they were. For example, from my house, to my west there is a large hill that I can't get my antenna above. I experience weaker signals from that direction in general. There are other areas when driving around that also get weaker signals in general, I call them holes. When I, or someone else, is on one of those areas the signal strength in s-units drops off noticeably, generally by several s-units. The modeling software is unable to pick up on these. However, there is a web site out there that take an antenna and give you a readout in your area what and where the local signal strengths would be. What was that web site again? I'll have to go find it again I suppose...


The DB

 

[Heavy Metal]

The choke I made my SWRs remained same no change whatsoever

 

[bob85]

Eddie,
as I posted in the past I have seen detectable improvements in local signal strength locally by isolating and adding radials to a99's and imax,

in both cases my buddies were suffering from lip biting rfi in the shack that was causing major issues with the radios and touch lamps etc, the issues were cured by using fork handle isolators a choke near feedpoint and radials,

if you don't have bad cmc to start with I doubt you would see any change in signal,

I like DB 's new angle on signal strength at distance, it more closely fits my own experience,

antennas do perform differently especially over longer local distances,
I would be interested in a 5/8 vs vector surface wave measurement because in my experience the difference in signal between the best 5/8 antennas and a vector4000 at say 40 miles is not only a small fraction of a db from this location,

 

[Marconi]

Eddie,
as I posted in the past I have seen detectable improvements in local signal strength locally by isolating and adding radials to a99's and imax,

I agree Bob, and I hope that is what I suggested earlier. I've also heard similar reports from others. I remember Multimode200 and his A99 with your "spider plane" ground plane idea and mast isolation being the only one that comes to mind, right now.

I think some of my Eznec models also show some far field gain by adding isolation and radials to the A99/Imax...but I've said I don't think the differences would likely be detectable just using a radio. I have never noticed a duplicate-able difference in my real world testing either, so that is another factor why I am dubious.

If I understood and knew how to measure antenna responses using "Surface Wave Measurements"...I might be convinced.

I like DB 's new angle on signal strength at distance, it more closely fits my own experience,

antennas do perform differently especially over longer local distances,
I would be interested in a 5/8 vs vector surface wave measurement because in my experience the difference in signal between the best 5/8 antennas and a vector4000 at say 40 miles is not only a small fraction of a db from this location,

If you and/or DB would reveal to us how you measure such antenna waves...that would be helpful I think, or is it so complicated as to be over our heads.

Help us out.

 

[Marconi]

in both cases my buddies were suffering from lip biting rfi in the shack that was causing major issues with the radios and touch lamps etc, the issues were cured by using fork handle isolators a choke near feedpoint and radials,

if you don't have bad cmc to start with I doubt you would see any change in signal,

Bob I have heard of such things, but I don't recall ever having RFI lip bite. Maybe some of the other things I have experienced though. Other than the nuance of this interference however...I can't recall ever noticing a big difference...compared to other antennas that did not act bad this way.

 

[The DB]

If you and/or DB would reveal to us how you measure such antenna waves...that would be helpful I think, or is it so complicated as to be over our heads.

For me it is a function in 4NEC2. It is available in EZNec as well, but unfortunately only in the very expensive pro version. When I select Surface Wave it asks me for a distance measured in kilometers, and a height measured in meters. Like the standard gain plots, it has two different views, the top down view looks very close to the top down gain view, although changes to an antenna have different changes to the two top down plots. The horizontal view, however, looks very different. Another thing to note is it measures the strength of a signal in milli- micro- or nano- volts per meter instead of decibels.

I see very little posted surface wave data. There are some web pages out there that talk about it, although most of them just give general information. Everyone seems to recognize gain plots, but no one seems to have any idea surface wave plots exist...


The DB

 

[Marconi]

Thanks DB, but I'm not sure I understand Surface Wave Measurements. I'm not even sure we've seen such 4Nec2 plots.

Bob suggested above that he liked your solution to measuring differences between antenna, and maybe you could make a Surface Wave Measurement model comparing of a couple of different antennas. How about instead...using an Imax and Surface Wave measurements...that proves there is a detectable improvement between an Imax antenna that shows CMC's, and same Imax after it has been fixed...similar to the questions in this thread.

 

[RadioDaze2.0]

"We" as in hobby radio users in general. Many think that low TOA has a correlation to good local contact as well as DX, and for the DX we know this is advantageous in general terms. Sorry for implying you were in that group of people if it offended you.

"Also, what is this we? I used to think that way, but haven't in quite some time. When I measure for local contacts I use a surface wave measurement, not a far field gain measurement. Even if you have a 5 degree angle of maximum radiation, how high is that going to be above the head of the guy you mentioned that is 150 miles away? The signal at that angle would be about 13 miles above the other stations's head, and that is assuming the earth is flat, as it is round, it would be even higher than that. Tell me, how would a maximum signal strength that is 13 plus miles above a guys head have anything to do with him on a local contact?"

So this is in essence what I have been thinking about and have in fact expressed elsewhere. (it largely fell on deaf ears) And this is where I believe my imaginings might actually have some value. I have always had quite a visual perspective on how radio waves work, imagining them relative to the sky and earth as they propagate. Of course there are limits.

It is a lot to take in I have to read and re-read this to understand some of what is written. Elsewhere I wrote about how a typical computer model has a clearly defined border on the lobes. An "edge" if you like, in essence a black green or blue line depict the boundary.

Given the suggestion that a signal lobe would/could be 13 miles or 2.5 miles above an RX station at distance.

Let us say any given model shows a max gain lobe at a nice round 10 degrees. Maybe that max gain at 10 degrees has nothing to do with what the RX stations receives at distance.

Maybe this clearly defined lobe "edge" going up at a diagonal from radiating element in the models is 100pct fantasy land. Maybe there is significant RF energy below such a defined edge on any given graphic's lobe ? Just a thought. And if so then such a model is without question inadequate.

The question is how does one measure this signal, as in the one that is actually being received and not some irrelevant lobe 13 miles above ?

We have understood cb and amateur sets to be next to useless, accuracy and calibration wise. So we come back once again maybe these things are impossible to measure and as such absolutes are simply "best guesses" in reality.

It also beckons the question of why this important RF energy is not modeled.

Real world operation seemingly makes a complete mockery of graphs (at least if we stick to line of sight or close to ground comms). Even though they can offer some basic insight and provoke further thought.

 

[Marconi]

I see very little posted surface wave data. There are some web pages out there that talk about it, although most of them just give general information. Everyone seems to recognize gain plots, but no one seems to have any idea surface wave plots exist...

DB, I found the subject in an article in the ARRL Antenna Book, editions #17 and #19 however. See it in the pdf file attached below. I high-lited the text.

To me it seems to indicate Surface Waves are of little to no use, a serious limitation, at any frequency in the Amateur bands, excepting maybe below 160 meters.

DB and Bob, if this Surface Wave idea only applies to very low frequencies, with very long wavelengths, then how useful do you think such measurements are for 11 meters?

I may can see the utility of such a feature in 4Nec2, Eznec, and maybe other such antenna software if properly applied, because such software packages are likely functional at very low frequencies...even below the Amateur bands.

However, this looks like a serious limitation to me...unless maybe some were working at broadcast and lower radio frequencies.

 

[bob85]

Eddie,
everything I have read says groundwave at higher frequencies don't travel very far from the transmitter due to ground attenuation, it used to amuse me hearing locals calling CQ groundwave when it was short hop skip,

it depends what DB's software means by surface wave measurement,
you would think that for the software to be anything like accurate on any frequency it would need to factor in a dielectric constant for the ground and a frequency to calculate attenuation of the wave or the downtilt ,

how much difference do you think not having a matching circuit with losses that closely model the real antenna makes ?

 

[The DB]

DB, I found the subject in an article in the ARRL Antenna Book, editions #17 and #19 however. See it in the pdf file attached below. I high-lited the text.

To me it seems to indicate Surface Waves are of little to no use, a serious limitation, at any frequency in the Amateur bands, excepting maybe below 160 meters.

DB and Bob, if this Surface Wave idea only applies to very low frequencies, with very long wavelengths, then how useful do you think such measurements are for 11 meters?

I may can see the utility of such a feature in 4Nec2, Eznec, and maybe other such antenna software if properly applied, because such software packages are likely functional at very low frequencies...even below the Amateur bands.

However, this looks like a serious limitation to me...unless maybe some were working at broadcast and lower radio frequencies.

Because I know how you operate I will tell you that you can convince me otherwise, and there is even more than one way to do so.

Method 1: Find me an article that deals with surface waves and modeling that says as much. It has to be an article that has to do with modeling, not propagation like the page from your ARRL Antenna Book, a section that has since been dropped from the newer versions of the book all together.

Method 2: Have HenryHPSD tell me that what he told me (and everyone for that matter) in a previous thread was wrong. It was him that taught me that the only way to model local ranges is through using surface waves, and one of his reports was the first time I've seen surface waves modeled anywhere, and it was for a CB antenna, go figure...

There is your challenge Eddie. I am not interested in arguing with another opinion of yours on a topic that you know nothing about and haven't even bothered trying to understand before forming a set opinion that even the likes of God can't change. Its nothing personal, but I've learned the hard way that such discussions with you only create migranes for me. I have posted multiple times in multiple threads (including this one) exactly why I use Surface Waves and their differences from the more typical gain plot, some posts of which you directly responded to. You seemed to understand why said plots were being used then...


The DB


Unrelated additional information...

There is actually another use of the phrase "Surface Wave" when it comes to antennas, although I highly doubt you will see it in any ARRL publication any time soon. It is referenced when working with some antenna types commonly found near one GHz frequencies and higher, and is a common antenna for modern cell phones. That being said, I have also recently seen a 2 meter ham band antenna design that is essentially the same type of antenna blown up in size, so I guess said use of the word isn't limited to UHF and higher frequencies...