ASTROPLANE best vertical antenna ever?

[nav2010]

I dropped out of this thread quite some time ago but just read something I have to bring up. In the case of a half wave dipole the inductance and capacitance are not cancelled out because it is a balanced antenna. Being balanced has NOTHING to do with it and the ONLY time the inductance and capacitance of ANY antenna is truly cancelled out is when the antenna is tuned to resonance. If the transmitter feeding that antenna is operated above the resonant frequency the feedpoint will exhibit inductive reactance but if it is operated below the resonant frequency the feedpoint will show capacitive reactance even in the case of a half wave dipole which is a balanced antenna. Being balanced has NOTHING to do with reactances cancelling out or not.

Certain antenna electrical lengths exhibit high inductance at the feed point and some exhibit high capacitance at the feed point. That is what the oscillator see's as apposed to a resistive circuit. When inductive reactance and capacitive reactance are equal at resonance they cancel each other out and the oscillator see's a resistive circuit. That's how I should have worded it, not balanced, you are correct.

 

[nav2010]

But just getting back to the AP and whether or not it behaves like a loop antenna. What evidence is there to suggest it doesn't act like a loop? The electrical installation and feed method is no different to a loop so why wouldn't it behave as such?

 

[The DB]

DB, my model of the A/P with no blue line requires a mast 240" inches long to in order to show a good match of 45.46 - J 0.008199 ohms at resonance and it could be even better. So, you are right about the mast needing to be made longer in the absence of the blue line in order to see a good match.

Is this 240" inches antenna mast length inside and below the radials even close to what you get with your model?

My mast length is 220". With that mast length I am able to take the stock dimensions and tune the AP to resonance. When I remove the "blue wire", I don't need to change the mast length at all, it stays at 220". It seems resonance is the key. On your model, assuming minor differences between out models, you may need to adjust this mast length to compensate.

I didn't adjust this model to show an SWR match to begin with, I used the stock dimensions and a mast length that showed optimal resonance. SWR was something like 1.3 to begin with and it went down after I removed the "blue wire". The only other change I made was to correct for AGT. I don't remember what it was pre-correction, but it wasn't anything like that 1.6 that you had.

Alternately, you can tune the antenna without the "blue wire" in the model, and after it is tuned you can add it in. That would be doing essentially what I am doing only in the opposite direction.

I don't believe we can remove this blue line wire from the model and just extended the antenna mast, and still expect any good results. I would hope you might shed some light of any error I made. This is why I keep asking if we are doing this model right using this trick...or should I say procedure for tuning a model.

Again, when I removed the wire, I didn't have to extend the mast.

The link to patent 3587109 below discusses this area in the abstract at column #4 lines 17-29, and is illustrated in Fig 5 on sheet 2 of 2. Both Fig 5 & 6 suggest and open loop idea, but in that case the feed point needs to be on wire #18 per the patent, the radial under the feed point on the real antenna.

According to the patent...

A coaxial transmission means or cable 37 runs up the vertical boom to level A and terminates in a coaxial connector 39 secured to the clamp assembly. A first transmission feed lead 38 of cable 37, its braided cover, is electrically connected to clamping element 25 and the inner lead 40 is electrically connected to split brass ring 36 (hence to the third conductor 18 at level A). The third conductor 18 is insulated from the first and second conductors at level A at which the clamp assembly 24 lies by insulative segments 34. Four bolts and nuts 42 are provided adjacent end portion 30 to compress segments 34 of the insulative bushing against each other to cause the split ring to engage conductor 18 tightly and to provide a secure electrical connection therebetween and at level A.

One side of the feed point is on conductor 18 and the other is on clamping element 25, which is eclectically shorted to the mounting bracket. That means that the feed point is exactly in the connection between these two elements. Because we can't put the feed point right in this spot, and for our own reasons you chose one side and I chose the other. We are both equally correct and equally incorrect here.

Perhaps, if you want your feed point to be in the corner instead of just on one side or the other you would put two feed points on your model, one on each side right next to the corner. I, however, don't see the point. In my experience with modeling I know that this won't make that much of a difference.

I believe I have workable model that has a feed point on this wire #18 noted in the patent. I will see if it works when removing one of the small wires in the mounting bracket. also as noted in the patent as shown in Fig #5, in particular.

The patent also talks about the bottom area of the antenna being a closed loop with possible construction as an open loop. Again see column #4 lines 26-29 for alternative details. I'm not saying that I have the understanding of this issue, but these words seem pertinent and clear to me and the images helps too. They do call this area a loop. However, I would not swear to this base on anything I've read in nav2010 post on this subject...just to be clear I said it earlier.

Again, Nav's image did it for me, and I can only assume that his words somehow describe what he as saying. My words here are not meant to be critical.

The first thing to remember is their are parts of the patent that we have demonstrated to be incorrect. This has happened to enough parts of the patent that I don't inherently trust what the patent states unless I can confirm it independently.

Until he actually tries to help with what I asked for, rather than going into pointless questions that I already knew the answer to (and him actually getting part of his answers wrong...) Seriously, why couldn't he have just helped with what I was specifically asking about, which was his weird use of terminology, (which he intentionally avoided doing). As far as I am concerned what he is saying is irrelevant. Even when it comes to the so called "facts" he posts, especially when it comes to loops, he is wrong on one of the most basic aspects (among others) of how a loop functions. Anyway, enough about him.

DB, below is my model that follows the idea noted in Fig #5 in the patent. I used this model with the full 1/4 wave because I had fed it at the top of the radial under the A/P feed point

Take a close look at the diagram listed in the patent and the wire layout of your model, you will see where their should be an open circuit their is still an electrical short because of the second wire you used for the bracket in your model that you failed to remove. That second wire doesn't appear in the patent, so to simulate what you are trying to do with the patent you have to remove that second wire as well. In your model you really didn't do much to the antenna, you just made the path between your feed point and the mast a few inches longer which is very different electrically to what they show in the diagram in the patent.

Actually having this second wire to simulate the bracket is strange to me, I don't see two wires like this in the patent or on the actual antennas. I wonder if this is a big part of the differences we see between our antennas?

Also, that is not the "blue wire" I am referring to. Do not confuse the wires that make up the two sides of the bracket, and do not assume the "blue wire" I am referring to has anything to do with anything in the patent, it doesn't.


The DB

 

[nav2010]

Until he actually tries to help with what I asked for, rather than going into pointless questions that I already knew the answer to (and him actually getting part of his answers wrong...) Seriously, why couldn't he have just helped with what I was specifically asking about, which was his weird use of terminology, (which he intentionally avoided doing). As far as I am concerned what he is saying is irrelevant. Even when it comes to the so called "facts" he posts, especially when it comes to loops, he is wrong on one of the most basic aspects (among others) of how a loop functions. Anyway, enough about him.

I'm just reading your posts, i'll just observe what you and Eddie make of the AP and let you decide between the pair of you. The AP is what it is.

 

[nav2010]

If you're wondering where the voltage maxima is on this antenna DB, you could always find someone with an 8 pil to key up on FM on the antenna then place both of your hands in various locations around the antenna. That'll find it every time.

 

[Marconi]

Thanks, I see what you are saying. I agree my model does not look like the one in the patent with all the extra wires. i will work on your suggestions, as they do make sense.

 

[The DB]

Eddie, a video response replying to a few things we discussed, and a comparison of currents between a half wavelength loop and the AP's loop.




The DB

 

[bob85]

DB thanks for the video response, i agree with your points on eddies model of the feed-point with blue wire removed,

I am having trouble seeing your 1/2wave loop in the astroplane construction,

when you remove the mast & upper 1/4wave of an astroplane you are left with a loop that's 8ft down one leg, 4ft across the hoop & 8ft up the other leg,
i make that a distorted 5/8wave loop with pretty high impedance & not a lot of antenna mode current flowing,

when you add the mast it becomes something entirely different imho,
it looks like a 3 wire transmission-line & seems to act like one with regards to mast length and removing the blue wire but i could be wrong,

if its not too much trouble can we see a model of a bottom fed 1/2wave j-pole
then the same antenna with the top of the stub shorted out.

thanks

 

[Marconi]

DB, this is a point of view that I would have likely never imagined had we not been discussing these issues. This is why I'm here of the WWDX, thinking I might learn something I didn't know.

When I said you had the feed point in the wrong location I did not mean it exactly as it came out in my words, sorry.

Just recently I posted several models with the feed point at various locations on the hub area of my A/P model...so I misspoke in saying you had yours in the wrong location.

You are correct saying I built the mounting bracket and the feed point location based on the way the antenna physically looks in this area.

Shortly before this thread started up again, I had been working on my model of the A/P and trying to apply a similar feed point idea as I imagined DB was using. I think your idea here is more plausible and it works. I still have doubts about our use of such a long mast extending below the A/P hoop however, but I doubt these models would work without them included.That said however, I recall the patent suggesting that the mast for the A/P might be on the order 7'- 8' feet below the bottom of the hoop.

For a long time I could match the model close enough to work safely for a transmitter, but I could never quite get a match like I got with my Old Top One knockoff version of the A/P out in the back yard. The "R" value of the impedance was always a little high for the model...typically up in the 60 ohm range. I don't know why I never saw the simple application you use. Now it's just plane common sense to me and it works fine as your model it.

I like your new look in your video...it is very effective. I'm not particular interested in the issues about the loop but the idea is well presented and important to understand. I hope nav2010 considers this information.

Frankly, I never thought of the bottom area of the A/P as a loop. I was thinking the bottom area was more like a feeder to an end fed 1/2 wave radiator, but I was never sure. I had in mind some sort of J-Pole.

Thanks for taking the time to do a video and explain a few things. For this old man a picture is worth a 1000 words.

 

[The DB]

I am having trouble seeing your 1/2wave loop in the astroplane construction,

when you remove the mast & upper 1/4wave of an astroplane you are left with a loop that's 8ft down one leg, 4ft across the hoop & 8ft up the other leg,
i make that a distorted 5/8wave loop with pretty high impedance & not a lot of antenna mode current flowing,

Here you go, just the loop that is on the AP for comparison to previous models.

I wouldn't call it a 5/8 wavelength loop, but it is definitely longer than a 1/2 wavelength.

when you add the mast it becomes something entirely different imho,
it looks like a 3 wire transmission-line & seems to act like one with regards to mast length and removing the blue wire but i could be wrong,

What is it is definitely open for debate.

if its not too much trouble can we see a model of a bottom fed 1/2wave j-pole
then the same antenna with the top of the stub shorted out.

Something like...

If I got it wrong let me know.

I still have doubts about our use of such a long mast extending below the A/P hoop however, but I doubt these models would work without them included.That said however, I recall the patent suggesting that the mast for the A/P might be on the order 7'- 8' feet below the bottom of the hoop.

I think the reason the mast has to be so long is the added capacitance from being inside the basket area of the antenna. Even though the mast is so long, if you look at the current distribution on said mast, it still goes from a voltage node on one end and a current node on the other, just like a 1/4 wavelength element.

For a long time I could match the model close enough to work safely for a transmitter, but I could never quite get a match like I got with my Old Top One knockoff version of the A/P out in the back yard. The "R" value of the impedance was always a little high for the model...typically up in the 60 ohm range. I don't know why I never saw the simple application you use. Now it's just plane common sense to me and it works fine as your model it.

Glad to be of help.

I like your new look in your video...it is very effective. I'm not particular interested in the issues about the loop but the idea is well presented and important to understand...

Frankly, I never thought of the bottom area of the A/P as a loop. I was thinking the bottom area was more like a feeder to an end fed 1/2 wave radiator, but I was never sure. I had in mind some sort of J-Pole.

Thanks for taking the time to do a video and explain a few things. For this old man a picture is worth a 1000 words.

Take a j-pole, fold the stub up a certain way, and you are close to an AP, current distribution and all. I think you, me, and bob all have somewhat similar ideas, but then we have been working on this together to some extent so I guess that isn't to surprising.

Thanks for the support, I want to do more with videos if I can, a lot more. I guess whatever we do we have to start somewhere.


The DB

 

[bob85]

Thanks DB,
i have been saying it looks like a form of inverted j-pole for years,

here's my thinking, correct me if im wrong,

the astroplane mast acts like a j-pole radiator,
when its 3/4wave long you have max current on the mast, * not connected to ground *

shorten the astroplane mast or the radiator side of a j-pole to 1/2wave you have minimum current below / above the stub respectively,

the upper 1/4wave of the astroplane acts like the mast on a j-pole,
when it is 1/4wave you have maximum current,
when it is 1/2wave long you have minimum current,

to me it looks like two inverted j-poles connected back to back with the 1/4wave stubs connected together at their open ends.

 

[Marconi]

the astroplane mast acts like a j-pole radiator,
when its 3/4wave long you have max current on the mast, * not connected to ground *

You're right Bob, a 3/4 wave radiator will show maximum current, but for some reason the upside down A/P Real Earth model, below, does not show much current on the radiator (mast)...so the gain is not up to par.

shorten the astroplane mast or the radiator side of a j-pole to 1/2wave you have minimum current below / above the stub respectively,

when it is 1/2wave long you have minimum current,

The 1/2 wave also does as you note, but I did not save the model. It also showed most of the current was radiating from the upside down A/P instead of the upside down mast in the top.

The models below:
1. You will also note the Average Gain is off a little. In the tuning process I kept reaching the tipping point where geometry errors would pop up...so I had to back up to the previous step and 0.974 AG was as close as I could get.

2. Shows the Free Space model that I did first. I did this model this way so I could first get the model to show a good Average Gain result. See the AG at the bottom of the Exnec Control Center image.

This FS model shows a maximum gain of 3.88 dbi @-15 degrees. It also shows a nice gain of 2.70 dbi @ 0 degrees. This FS model obviously shows a tilt in the pattern below the horizon .

3. However, when I set this FS model over Real Earth settings the gain was not so good anymore, showing 2.13 dbi at 8* degrees above the horizon. However, at 36' feet to the feed point...this maximum 8* degree angle is very good.

 

[BOOTY2]

if a astroplane and a vector 4000 are mounted at the same feed point , which will typically do better ? or does the astroplane need an additional 27 feet of mast (same tip height) to compete with a vector ?

 

[Marconi]

if a astroplane and a vector 4000 are mounted at the same feed point , which will typically do better ? or does the astroplane need an additional 27 feet of mast (same tip height) to compete with a vector ?

Booty2, this probably won't give you pause to consider...but check it out since you asked the question.

The differences in tip heights between these two is very close to 23' feet (FP's are 59' - 36' = 23') not 27' feet.

If you look carefully you will see that the Vector has over 57% more height in the air than the 12' foot tall A/P. You will also see the maximum current lobes are close to being equal in height when I set the tip heights equal. This is why we see little to no difference that matters when the antennas are fairly considered. This is also likely what we might see if I laid both antennas down on their sides horizontally.

The Vector shows a slight edge in the gain, but you would be hard pressed to detect such a small difference...just using your radio. I concede the fact that the Vector is a great antenna high in my opinion. I also state if these same two antennas were set in height at the same feed point heights...there would be little to argue...that the Vector is a superior vertical CB antenna.

 

[The DB]

if a astroplane and a vector 4000 are mounted at the same feed point , which will typically do better ?

As I recently lost all of my models, I haven't yet remade the Vector model for comparison, so I'll leave it to Marconi. That being said, if you are talking the same feed point height, the longer antenna will pretty much always outperform the shorter one, at least to some degree, and if that isn't the case you likely have a problem with the longer antenna that needs to be dealt with.

or does the astroplane need an additional 27 feet of mast (same tip height) to compete with a vector ?

As Marconi stated above, it isn't that much extra mast, but yes, to compete with pretty much any vertical antenna this antenna is intended to be mounted at the same tip height. The patent states this and models by Marconi and I also support this. The Astroplane will actually outperform most antennas when mounted this way because of the cap hat, which has the effect of elevating the current node higher than other antennas at the same tip height by a few feet, and the current node is the important part when determining gain.

That being said, at least for local contacts, HommerBB has stated that the only antenna design to beat the Astroplane when when mounted at the same tip height for local distance contacts was the Vector, and with his extensive and open history of building antennas, I have no reason to doubt his claim. While the Vector was his best performing antenna, the Astroplane was his favorite design.


The DB