sigma4 article is online

[Shockwave]

I see nothing that suggest this process is in any way steering the TOA. IMO these effects, of ultimately seeing a 0* degree pattern at the horizon, are entirely due to the antenna reaching an overall length we would see from a moderately well balanced length center fed 1/2 wave radiator and nothing more.

I sure didn't see anything suggest this process would go below 0* degrees on the horizon however.

My eyes, field strength receiver and ability to place a signal where a well constructed 1/2 wave could not simply by adjusting these lengths, do much more than make the suggestion of beam tilt. Before casting something tangible away in favor of opinion, you might want to model some well known examples utilizing electronic beam tilt and notice how they DO NOT differ from what you're seeing with the Sigma.

Model a pair of stacked dipoles in free space and delay the source to the top one by -5 or -10 degrees. Now switch from free space to real ground and you'll see most of the tilt no longer appears in your model. Do you think this means the array cannot have its TOA electronically altered over real earth too? If you do, you've just disagreed with more than 50 years of successfully using this method of beam tilt on FM broadcast.

 

[Marconi]

I feel like Henry now...where do I start.

 

[Marconi]

Sorry I haven't had time to read Henry's report, comment or answer messages.

I have been quite ill recently and had a bit of a fall early last week that resulted in an unscheduled collision with a glass tv stand, a floor standing speaker I decided to glasgow kiss on the way down and a collision with a clr2 that i had lying on the floor. Suffice to say they won.

I'll catch up on Henry's report, answer messages and stick my tuppence worth in soon.

Sorry for not being about as much as I'd like. Looks like I've missed out a fair bit.

73 Jazz.

Jazz, sorry to hear about your accident. I won't even ask what is a glasgow kiss.

 

[Marconi]

Not this again. Do you really think I use umpteen thousand segments in every model I create? My standard segments per wavelength is in the range of 100 per wavelength, and that is simply to make it easier to maintain a given segment length in the models I make. In the models above it is 50 segments per wavelength, which is even less. You have also completely missed the how and why I use the element diameter that I use, and have ignored me on multiple occasions when I said that they are for theoretical and initial purposes only. As I work with models those thin diameters get thicker, to the point of a real world antenna. I have told you these things before...

Well you touched on it, Henry wrote a whole section devoted to the idea, and I was reminded of the idea again. Since it is an important limitation that is noted in my Eznec manual and you guys are always telling me about these limitations...I think the idea may bear repeating.

I remember Homer discussing it and saying he though it made a difference based on the versions of the Vector he made, and Donald saying otherwise. I have found on multiple occasions that the versions of models that include a hub have a slight increase in gain as well.

I don't recall Donald's input back then, but everyone is entitled to his own opinion. I did not look at the addition of the hub design in reference to gain, but it does seem to have such an effect that influences gain, and a 1/4" difference, more or less, seems to matter.

So, yes I see it as important to the consider in this model, but I'm also saying here I can't be sure how it responds in a real model. I don't know what Homer or BM will say, but I recall that coming up as they built and tested their Vectors.

I was steering the TOA in a freespace environment. I have not yet tried to do the same with this model over an earth. I think attempts to steer the TOA over an earth will have far less of an effect if I can even do it at all. That is why one of the modifications I did to the model was a height adjustment, so I can easily set the height over an earth. When it comes to models, performance isn't all I look at. there is plenty of other good info available forma model.

I agree that your steering the maximum TOA in a model designed over real Earth might not show up. I also don't see it in free space models...where height above real Earth is totally omitted from the model. I also don't consider raising or lowering an antenna over real Earth as steering either, but I know the effect does happen.

Soon, I will publish my antenna field notes on the subject...and that should make the matter visual, and a bit more clear for the readers.

Thanks for you comments.

 

[Shockwave]

While using the hub at the base in the model may improve model results dealing with the acute angle, I assure you this is not the case with the real antenna in the field. The more you space the radials away from the base of the antenna, the more performance drops and it requires more capacitance in the gamma match to correct the impedance change.

The difference is very small but the best results are achieved when the radials are attached directly on the base of the monopole. Test results have shown that sharper angles provide more gain however they also make the loop larger unless you can increase the angle from the base. When the loop gets larger, the electrical length of the cone also appears longer. The problem is its physical length becomes short enough that it can no longer confine all of the out of phase field within the cone.

 

[Henry HPSD]

Owh guys...so much lines...
Donald did you read my reply ?

There is no debate whether or not downward tilting is useful in some cases.
But that would not be for CB.
It is used for example in FM broadcast where the antenna in a situated on a very high mast (or cellphone communication) or "upward" tilting is used for example if the radio station is in a "vally"
The "direct wave" overshoots the desired target area.
The "key word" being direct wave.

Now did you do what i Asked ?

Attached a PDF with a SINGLE dipole showing downward tilt in free space and the plot in a "real" situation above earth.

In aspect to the hub:
Im looking at your dominator antenna.
And clearly see a 'hub" at the bottom don't I ?
Now that "hub" is much larger compared to the I used for analysing as "mine" was focussed on CB. (cb.. hence large wavelength, smaller distance)



Im not confident you understand what "earth" does in aspect to our free space antenna plot.
I base that on: just because the effects are reduced with ground reflections. ?
What makes you think the effects are reduced ?

Again asking please look into things like pseude brewster angle, instead of repeating the same out of contex mistake.

Please allow me to quote "Cebik" when he mentioned the angle in aspect to modelling:
For modelers, the introduction of the crude PBA calculation should take the mystery out of elevation patterns for vertical antennas, especially those well above ground. Those who have only modeled a few such antennas may wonder whether the depression region is a software problem or a problem with their particular model. Actually, it is neither. Rather it is part of the normal propagation of far-field radiation. (Horizontal antennas do not share this effect, at least not in the same way or to the degree shown by vertical antennas.)
End of quote.


Oke..
Now, what will happen if we start tilting a yagi beam downwards ?



(click to enlarge)
maximum gain will drop and angle will go up..

Now, we can continue the search in "more" downward tilting...(which is perfectly possible with a single radiator, no collinear effect needed ) but it will only enhance signal strength at close range and will reduce the overall "reach" and maximum strength at distant horizon and maximum ability to DX

And we havnt began to talk bout what is that you think you changed ?
Is it truly the antenna ? or were there perhaps possible issues ?
Did you have a mechanical pole underneath it ?
(not needing to be "dc connected by the way) ...just in the proximity of the antenna is fine with me...Are you confident the coax was isolated ?
How did you now you were not "tuning" reflected waves at the receiving location ?
Etc..etc. etc..


Kind regards,

H>

 

[Marconi]

In freespace with most antennas you have a maximum gain at "horizontal", or straight out from the antenna. With this antenna that isn't the case. Making changes to this antenna in freespace will change the angle of maximum radiation. You don't see this as steering the pattern, yet it is possible to, at least in freespace, aim the pattern at a certain angle. To me that aiming is steering the pattern. If you choose not to call it that, that is fine. All of this may or may not be moot over an earth for this model anyway...

I agree, in this regard, the idea with a real Earth model is likely moot, but I question that most antennas modeled in Free Space show a pattern at 0* degrees to the horizon. Even EFHW's show a bit of increased angle above the horizon. Center fed's are better and are most often at 0* degrees. My Marconi x, A/P, Starduster, New Top One, Merlin, CFHW dipole, and GainMaster all show 0* degree maximum TOA in Free Space. What is common among all of these?

All of the rest of my vertical CB antenna models vary as to the maximum TOA and they are all above the horizon in Free Space models.

IMO, this suggest the models that are balanced by design show better FS results at or near 0* degree.

Since my New Vector 4K shows a very low TOA in free space, I suspect this may be what caught the attention of the engineers who designed the new Vector. I also consider it possible that Donald saw something in his testing and design of his antenna that suggested the same thing (better balance).

I still don't believe this is a controllable feature subject to tune or some adjustment. To be specific, I think the characteristic has mostly to do with better balance designs. I also think it is a mistake to consider that any of this could be controlled or detected just using our radio...unless we have acceess and understanding of very high tech measuring devices at hand. IMO, for us to discuss this as a casual occurrence that can easily be adjusted and controlled like a clock...can be misleading to most readers...and to be frank...I consider it mostly smoke and mirrors.

Concerning TOA, I believe the only method we have to steer or control the angle is by simply changing the antenna height, and at our level in the hobby, we are just NOT likely to have much more control.

I was able to manipulate this model in two completely different ways to get a "below horizontal angle" in freespace, so it is definitely possible to do. When I get a chace to get an earth under this antenna I will see if, and potentially how much, this model will allow manipulating the angle of radiation...

I haven't seen any of these type of effects DB, but your results would be interesting.

 

[Henry HPSD]

@ Donald :
The problem is its physical length becomes short enough that it can no longer confine all of the out of phase field within the cone.

Oke, I think i have explain the CST plot pritty wel, what is it you do not understand ?

Lets do it otherwise...proof me wrong
Provide for example a nice CST plot of the antenna in free space in dBI gain like i have done.
Or please give me other "real" proof ...proof not being "i have seen it in my fieldtest"..
Not that i dont believe that you believe your field test is accurate...but i cant do anything with it
And I really have done now everything ...and no I did not find any collinear gain as we imagine collinear gain to be.

Kind regards,

H>

 

[The DB]

When I play with the antenna over an earth, at one wavelength high, I do not see an change in radiation angle of the low angle lobe, at least not enough that a 1 degree resolution is picking up. I am seeing the the changes that in freespace would lower the angle of radiation make the lower lobe more dominant over an earth. This strengthening of the lower angle lobe comes from a weakening of the higher angle lobes. Also, the angle of the higher angle lobes are changing, and pointing higher up. This change in the higher angle lobes angle is not unexpected based on my previous experience with modeling.

I'll have to try this at a higher altitude, say 10 wavelengths above the modeled earth, and see if I can get a change in far field radiation angle.

Is it possible that there is a closer in field (beyond the horizon diagram that NEC2 shows us) that is pointed more toward the earth? Yes.

Does NEC2 have the ability to map such a field should it exist? Not that I am aware of.


The DB

 

[Marconi]

Here are my iterations for changes in length for the radiator on my New Vector 4000 model, which the stock length, is 317.5" inches at 27.205 mhz.

This was done to see how these changes in radiator length effected the TOA, match, SWR, Gain, and Average Gain for the model. We do see the TOA changing angles, but it is not in any constructive manner as I consider these changes and the angle never looks to go below 0* degrees to the horizon.

• 
  

  Radiator  Radials    Gain     Angle   R       X      SWR      A/G
  
      222.5"  107"    2.23   @   0*   433.6    -48.9    8.80    0.000
      272.5"  107"    2.49   @   0*    80.5    -92.0    4.10    0.000
      292.5"  107"    2.56   @   0*    50.7    -49.5    2.58    0.000
      302.5"  107"    2.56   @   1*    41.6    -30.5    1.98    0.000
      312.5"  107"    2.52   @   2*    34.9    -12.7    1.58    0.000
      317.5"  107"    2.49   @   3*    32.3    -3.1     1.56    0.000
      318.5"  107"    2.48   @   4*    31.8    -1.4     1.58    0.000
      319.5"  107"    2.47   @   4*    31.3    -0.2     1.60    0.000
      320.5"  107"    2.46   @   4*    30.9    +2.2     1.62    0.000
      321.5"  107"    2.45   @   5*    30.5    +3.8     1.66    0.000
      325.5"  107"    2.40   @   6*    28.9    +11.4    1.85    0.000
      330.5"  107"    2.34   @   8*    27.3    +20.1    2.23    0.000
      340.5"  107"    2.27   @  16*    25.1    +38.7    3.40    0.001

 

[bob85]

I can't argue with what Henry is saying,

There is not doubt i can manipulate signals , not just me but several friends, and its easily seen on our radios,
Two masts tests with an antenna switch are meaningless, using ssb in unstable conditions introduces more vagary or CB bs if you prefer that terminology as some seem to,

I believe Henry is correct, What i originally thought was the likely cause was incorrect,
I misinterpreted the CST plot and underestimated the effects of current maxima above ground,

Something other than what i originally thought is causing the effect when i adjust my sigma4 style antennas.

That does not change the fact that a sigma IV or vector 4000 can outperform any 5/8wave when mounted on the same mast at typical antenna heights for a CB user,

In my closing statement in the alternative viewpoint post i said,
"until somebody shows me an alternative"

Im satisfied that somebody has shown me an alternative explanation unless you can prove otherwise.

73
bob

 

[Marconi]

I can't argue with what Henry is saying,

Bob, I don't find anything in question with Henry's report either, except the point I've raised in question about GHZ24's model.

I was really surprised at what Henry had to report. I just wonder what it was for you, however, that was so convincing to cause you to rethink this issue?

There is not doubt i can manipulate signals , not just me but several friends, and its easily seen on our radios,
Two masts tests with an antenna switch are meaningless, using ssb in unstable conditions introduces more vagary or CB bs if you prefer that terminology as some seem to,

Bob, for a some time recently you have told us about your ability to manipulate signals, and you tell us that others around you are also able to do the same. I guess you shared your ideas with them and they are able to report the same as a result. Why don't you do that with me, and maybe I can again report the same as you...like I use to do?

Before that I recall you telling me this idea had something to do with the way you tuned your Vector Hybrid, and that was not the same at different locations. I and others use to ask you what you did in that process, and again you told us what you did at your location would not help at our location.

Now that this is all out in the open, can you now tell us what exactly you do when you manipulate signals?

Is it something to do with your antenna tune and/or construction?

Or, does it have to do with how your radio is setup...so the meter is not at the mercy of a rf gain control or a cut back circuit that I hear guys talk about?

Jazz and I just recently had a discussion about how over in England a lot of guys have done a modification to their radio meters that allow the meter to detect a much smaller signal difference on the order of 1 db rather than the 6 db I hear the regular CB radios are able to report. Is that what all this is about?

I also remember you telling me that you would send me something that I could use with my radio that would make my radio meter able to record small differences in signals too. Whatever happened to that idea?

 

[Shockwave]

Forgive me if this seems stupid but how would one check to see if an antenna could produce an angle below 0 degrees over real earth when the plot for real earth contains no information about the region below 0 degrees? It does not seem possible for the program to indicate that reading above ground.

Before you bother to see if the Sigma shows the expected results for downward tilting over real earth, I suggest you become familiar with what arrays using ELECTRONIC beam tilt look like in EZNEC before thinking the Sigma is different. I've tried several systems proven to produce downward tilt using stacked dipoles and nothing you can do with the models seems to indicate this over real ground.

It's also important to understand the goal typically is not to produce a downward tilt below 0 degrees. On the other hand if a dipole produces an angle of 0 degrees in free space and 5 degrees at a given height and you replaced it with a Vector that shows - 5 degrees in free space, you will see more energy is focused closer to the horizon even though it's not at 0 degrees.

 

[Henry HPSD]

@ DB
There are "options" however Im not sure if 4nec2 handles them in a way you are asking.
I know the "pro" enzec version does.
But it could very well be the 4Nec2 version handles the different "waves" seperatly.
Ill ask Arie, if he remembers how it is implicated. And come back to you on PM.

@ Donald,

What makes you think it doesnt ?
Enzec PRO is perfectly capable of showing.
Now, instead of Asking me to "investigate"... cause I have done my homework..
Why dont you try to search before you say something.

Each time you provide warnings, which of course are appricitated, though..
Each time I can tell it is not correct and
Each time I need to proof you are not correct.
Each time You are not saying anymore "thank you for pointing out and correcting me" but
Each time you are trying to come up with something new

Would you say that is fair any longer ?.
Not once do you seem to do anything I have asked to..

....could you please do Donald... thank you.

Kind regards,

Henry

 

[bob85]

Eddie,
you keep steering me off topic and id rather not do that and pollute the thread, one more time, The last time,

I have always claimed i could manipulate signals ever since day 1, i cant prove it because the posts were lost when we changed servers years ago,
They are not on (archive.org wayback machine) either but there is some enlightening stuff on there,

I have explained what i do plenty of times, so has Donald, MC once complemented me in a sarcastic way about all my hard work making all those incremental adjustments,
there never was anything hidden to be "out in the open", no half truths no subterfuge,
Im bob85 not david copperfield,

Any discrepancies if they exist were purely accidental and not a deliberate act of obfuscation on my part,
contrary to what you believe ALL i ever wanted was the truth,
I have always said im willing to learn and change my opinion based on that learning, you can teach an old dog new tricks if the old dog wants to learn,

Finding the truth is difficult when the people doing the models can't answer simple questions about EZNEC capabilities and don't seem to understand what they are looking at with regards mast common mode impedance ( bad mast lengths ),
I had to find out for myself that EZNEC could handle common/antenna mode & transmission-line/differential mode currents, when i learned that i posted that it could on here,

Henry answered my other questions for which i am grateful,

Distributed capacitance to ground and surroundings can cause the same antenna to tune at different lengths in different locations on different length poles just like a mobile whip won't tune at the same length on different vehicles or positions on the same vehicle,

other factors such as common mode on the mast or feed-line can also upset the tuning,
different diameter monopoles and or radials have an effect too,

6db /s-unit is an old myth just like the 5/8wave gain myth,
I have never seen any radio that gets anywhere close to the old standard, my jrc135 is the closest @ about 3db/s-unit,

you don't need to modify the cb radio,

most cb's derive their s-meter voltage from the rx agc circuit,
the none linear conduction curve of a diode feeding the meter exaggerates the none linear meter response seen when signals are below and around the knee in the diodes curve,

I posted a link to swizzradios recently to show the effect and him swapping the diode for a germanium diode with a lower turn on voltage that reduces the effect,
The only rig i ever modified to show MORE change is my (short range no antenna) fox hunting rig by detuning the front end,

You don't remember me saying i would send you a device to allow you to see more change on your s-meter because that never happened,
Back your rf gain down to put the signal below the knee in the diodes curve if you want to see more change on the s-meter for a given change in signal strength,

This is the device i said i would send if i had the ferrite so that you could test common mode on your coax rather than rely on your field strength meter which is useless for that purpose,
http://www.w8ji.com/building_a_current_meter.htm

About that time i persuaded you to clean your sigmaIV that you told me you bought used and already assembled but split into two parts for transport that had never been cleaned since it was manufactured,

you inhaled the dust and ended up in intensive care, i felt bad that it almost killed you,
Ever since then you have been in no position to make any measurements on antennas and certainly not in good enough health to make many dozens of adjustments to your sigmaIV, things may have been different if that was not the case,

Its been fun, we had our ups and downs, its time for me to move on, there are better "true collinear"antennas to think about.

please print this out and pin it to your wall so we don't have to rehash it again,

thanks.