Any Astro Plane Fans ?

[bob85]

i don't know for sure what the patent means by closed conductive loop eddie, i took it as meaning remove the gap at the feed-point and feed it some other way,

when i say i don't see the astroplane like a starduster i mean they can act similar but arrive at that similarity by different means,
a 1/2wave dipole gives similar results to a folded dipole but they don't work the same way.

 

[Marconi]

the AP in the photo is not isolated from the mast, however the metal mast is isolated from the earth 10' above the ground. The wood part of the mast only
is below that.

Homer, that is another good point that I didn't consider. My new model, that really shows some promise with the feed line and the choke I made for Bob's model at 52' feet, has the feed line isolated as well.

When I attach it to the Earth however...the model goes to heck in a hand basket...and that usually means an error in the model, and this is why I haven't posted it yet. It might mean nothing as the real world goes, but it only works as a model in that position.

I think that is the point Bob was making the other day when he said my model looked to be sensitive to the mast and feed line. I could be wrong about the last part, because I haven't quizzed him in my usual way yet.

Thanks for the added info, I just can't think of all the possibilities by myself and your work has help me in that.

 

[Marconi]

i don't know for sure what the patent means by closed conductive loop eddie, i took it as meaning remove the gap at the feed-point and feed it some other way,

when i say i don't see the astroplane like a starduster i mean they can act similar but arrive at that similarity by different means,
a 1/2wave dipole gives similar results to a folded dipole but they don't work the same way.

Yes Bob, that is why I glaumed-on-to that statement by Avanti in the A/P Patent I posted...it says the same thing for me.

Just to be sure, when I hear folks, that probably have never compared antennas, make the claim that the New Top One is not the same or similar to the original Avanti A/P, this is what I present in support of my thinking, these little words from the Avanti guys. They didn't say these words for nothing.

Bob, these guys may have puffed some about their ideas and antennas, but they were smart as a live fox.

 

[HomerBB]

Homer I didn't even think about you using a choke on your A/P. Could you give me your choke dimensions, coax, and VF you used.

The choke is RG58, 5 wraps on 4.25" core. VF .67

 

[HomerBB]

I believe what is meant by a closed conductive loop is a complete closed loop that is fed at two separate points. Some circularly polarized antenna elements are fed this way, with predetermined degrees of difference of current through one feed leg and the other to stimulate circular TX/RX on the closed loop. Apparently this can be done with a closed loop because of the differently phased conductors feeding the closed loop.

I believe what this means in the AP patent is to be seen as an explanation of the similarity of the NEW Astroplane design in all respects to a known antenna design except the unclosed feed point of the AP. Bob makes a similar statement when he says the AP and a StarDuster behave similarly but achieve the behavior by a different means. As Bob is using the SD as a point of reference, so is Avanti using the referenced Closed Conductive Loop to provide perspective for the AP.

Another interesting observation noted in the patent to which I believe Bob has been referring is this quote: "The conclusion to be drawn, therefore, was that a mast having a length below level B of about one-quarter wavelength, i.e., about the length of the conductors I6, 18 gave an optimum takeoff angle."

Level B of the antenna is the loop. At 27 MHz 1/4ƛ is about 9'. So the patent is not saying the height above the ground is 9', but the optimum length of the mast below the loop is 1/4ƛ, or 9' at 27 MHz.

(Eddie, the patent says all the tubing is 1/2" diameter in the antenna. The cross pieces of the cap hat I recall is about 3/16".)

Also, the mast of the antenna need not be of a conducting material if coax is used, but the coax must be taped to the non conducting mast straight down the side of the mast. Of course, following the previous statement regarding the 1/4ƛ length of conducting mast terminated at 1/4ƛ below the loop, logically, the coax would need to be choked at 1/4ƛ below the loop also.

Hence, Avanti intended this antenna be set up for maximum performance at the highest legal tip height with a conductive mast of 1/4ƛ below the loop isolated from any other conductive mast or mount point, or use a non-conducting mast all the way to the antenna bracket and terminate or choke the coax 1/4ƛ below the loop.

Naturally, if one can not get the tip of the antenna 60' into the air he will do his best to get it as high as he can and still follow the patent statements of isolating the mast and/or coax 1/4ƛ below the loop.

In the patent the mast is clearly stated to be one of the conductors, an integral part of the antenna itself, but should not be longer than 9' below the loop without isolation.

 

[HomerBB]

Notice the Choke, or isolation point 1/4ƛ below the loop in the drawing from the AP patent. The drawing is not to scale, and the numbers of the parts are not dimensions. The numbers are the labels of the antenna parts in the portion the patent that is explaining the makeup of the AP. The mast is called Conductor #14.

 

[Marconi]

Homer, Bob's dimensions for an original A/P do not agree with your measurements.

On the Internet sheet that you and I have referred to...the dimensions are not for the original A/P, and they are different from all of our measurements. If you look carefully at this schematic, you will see one sure clue, and that is the radial is one solid piece of aluminum that is 93.1" x 1/2" inches overall. I think I asked you a question about how many pieces made up the radials the other day, and I think you said 2 elements. That was when you were talking about tuning your A/P by moving the bracket up and down some.

You see now how confusing this can get, and asking someone with good intentions for help measuring an antenna on the Internet...can be dubious at best. Over time I have measure some of my own antennas, and later when I go back to check a measurement...I might find I measured or wrote down something wrong...stuff just happens.

Bob's radials are 2 x 48" x 1/2" = 96" inches long for each radial,
OTO has 43.875" x 1/2" for the top and 44" x 1/2" for the bottom = 87.875" inches.
You suggest your A/P radials were 108" inches long.

You figure the top hat elements are 3/16" = .1875" inches.
Bob says they are 4 wires x .125" x 24" inches.
My OTO's are 2 wires x .125" x 47.75" inches.

I'm not real sure, but I don't think either of you gave me a measurement for the shortened radiator on top.

I'll get back on some of my ideas on the rest of you observations in another post.

So, I still don't know for sure.

I think Bob got his dimensions from a friend however. If that is so, we could still find differences. So I'm still not sure until Bob actually measures his real Avanti A/P. I've already found little error that I made in entering the data into this model, and I see improvements sometimes and sometimes I see the model go the other way.

Eznec is a powerful product and now most on this forum have been lead to believe that Eznec is not worthy to use. If does have limitations, but it also requires a serious effort if one really wants to get some real accuracy. That said however, Eznec is a pretest tool that can produce as intended, but field testing is always recommended.

Working with this tool requires more than a casual approach if accuracy is the goal. Roy Lewallen simply programed the user interface for the NEC engine...likely no small task, and his goal was to make the use of this NEC engine easy and intuitive for the user.

All of the dimensions can be made to work, but I wanted to try and get accurate dimensions where possible.

I thank you, but maybe Bob will get around to getting me the measurement, before Spring...or else he may forget and I will never get this one right.

 

[Marconi]

Notice the Choke, or isolation point 1/4ƛ below the loop in the drawing from the AP patent. The drawing is not to scale, and the numbers of the parts are not dimensions. The numbers are the labels of the antenna parts in the portion the patent that is explaining the makeup of the AP. The mast is called Conductor #14.

When I saw the squiggly marks at the bottoms of the mast #14 in the images you note above, I had the thought that mark meant the line was truncated (to be continued.) I never thought about that mark being a choke or a coil. If it is a coil, I wonder why the Patent doesn't say a word about it. Like Bob has suggested, this Pantent contains some technobull...and maybe this is and example.

If not somebody will have to prove that this antennas TOA can be steered like I saw in the model when I set it 4', 3',2',1' foot from the ground and observed the TOA change 1* degree with every iteration.

In the image below is the patent, and on column 3, line 42 to 54, is the discussion on element #14 that I think you refer to. You could be right, but I don't read these Patent comments the same as you, because I don't see the antenna working like is suggested only when the antenna is close to the Earth.

I think the folks at Avanti were talking about mounting near the Earth, and it seems the suggestion was that the closer we get the higher the TOA will be. IMO, this applies to any CB vertical that I know of a as a general rule as we make the mast longer the TOA drops and as we make it shorter the TOA goes up.

Bob and I talked about this and I did some testing with the model mounted 9' feet above the ground. I also did 4', 3', 2', and 1' foot, and I reported the TOA rised up 1* degree for every iteration I did lowering the antenna making the mast shorter. I also noticed that the match also went to heck in a hand basket dramatically with every 1' foot iteration lowering the antenna. I then did the same thing on raising the whole antenna to 32' feet or more, and of course I did no longer saw this same affect...the TOA was dropping very little as I raised the antenna..and the TOA was dropping very littel as I lowered the antenna...just like the article suggested in the last statement.

So Henry, IMO this information in the Patent could have only applied if and when we were working with the antenna very low to the Earth. When we change height (the mast length) for most CB verticals...we will see a little increase in angle, maybe 1* degree every 10' feet or so, but we surely aren't likely to see a 1* degree change with every foot of change.

This said however, I know there are folks out there that believe this antenna's TOA is steerable somehow, and this effect can possibly be somewhat remarkable in that effect.
I just disagree.

 

[bob85]

i thought you had shown that shortening the mast below the hoop caused Needle Benders setup to tilt the pattern substantially upwards in EZNEC eddie?

 

[Marconi]

i thought you had shown that shortening the mast below the hoop caused Needle Benders setup to tilt the pattern substantially upwards in EZNEC eddie?

Bob, you could say that if it makes you happy.

Here is what NB said and I tried and followed his idea to see how it effected my A/P model. The TOA went up, but the RF that was supposed to be on the antenna showed up on the mast. What happened was due to the high angle produced by the currents on a long mast that was likely not resonant at the frequency of choice.

I eliminated most of my local TVI/RFI by using 1.25'' diameter solid fiberglass rod to isolate the mast 105" down from the mounting bracket on my Avanti AP, since the mast is the 1/4 wave counterpoise for this folded 3/4 wave GP. I used 5.5 turns of the coax on a 4" diameter former for the cmc choke around the fiberglass.

Also as a result of this happening the match went terribly bad with very little resistance and a lot of reactance. You could probably fix that, but in doing so...you will develop a lot of losses and then as you get the match closer to being good, the TOA will come back to close to where it belongs and you might end up with just a lossy antenna. So you isolated your antenna and added a choke for nothing.

You would be better off if you want to claim you are steering your antenna's TOA, by mounting your antenna as low as you can get it. Mounted on the ground might make a TOA at about 30*- 40* degrees, and then you could raise it up maybe 10' feet at a time, and tell everybody you are steering your antennas TOA. That's fine with me if it makes you happy.

Bob you need to get this steering idea out of your thinking.

There is no magic going on with these antennas. The magic is being able to talk to someone a long way off, and do it thru the air without wires or having to raise your voice.

 

[bob85]

IM not trying to steer anything eddie, im hoping to minimise mast currents that could spoil the pattern,

the patent claims the pattern can be tilted 10-15 degrees below the horizon by removing the flare ,
i don't know if there is any truth in the claim, its not my idea,
its in the patent,

all im expecting from the astroplane is 1/2wave performance with a 4ft in height advantage of current maxima over other antennas mounted at the same tip height,
that could be an advantage at this location.

 

[The DB]

First things first, I want to say hi HomerBB. It is good to see you posting again...

Interesting thread. I have never directly played with an astroplane, so am taking the sidelines for the astroplane discussion. That being said something has come up that I feel should be addressed.

Eznec is a powerful product and now most on this forum have been lead to believe that Eznec is not worthy to use. If does have limitations, but it also requires a serious effort if one really wants to get some real accuracy. That said however, Eznec is a pretest tool that can produce as intended, but field testing is always recommended.

Working with this tool requires more than a casual approach if accuracy is the goal. Roy Lewallen simply programed the user interface for the NEC engine...likely no small task, and his goal was to make the use of this NEC engine easy and intuitive for the user.

I disagree that most on the forum have been lead to believe that EZNEC, or any version of NEC for that matter, are not worthy of use. I agree that they are useful tools, however, to say that there has been an effort to say they are not worth anything is clearly false. What has been claimed, and put forth, is that there are times that the NEC engines, in all of its forms, are unable to show what happens in reality. This is a true statement, and can be demonstrated as a fact in any number of areas and ways.

If you build a model in NEC, then build the antenna and it works very differently to what NEC predicts, do you believe NEC or what happens in the real world? That is where people that are arguing against you are coming from, you are choosing to believe a simulation software over what multiple people are actually experiencing in the real world.

In the case of this thread, you are seeing from your models what people are experiencing in the real world, so your models here are valid. In the case you are indirectly referring to above, you have your models, and you have very different real world results from multiple people that before said discussion, who when it began didn't know each other, and even now only know each other through discussions on this forum. There are also reports from others on this and other forums that agree with the real world results they are claiming.

So it comes down to is the models correct, or is what happens in the real world correct? There is only one correct answer to that question.

Sometimes a tool, no matter how good or powerful of a tool it is, it simply the wrong tool for the job.


The DB

 

[HomerBB]

Orion industries/Avanti patent filed 1968, published 1971
Read this one to find the referenced choke, 1/4 wavelength mast out the bottom. It's in there.


http://www.google.com/patents/US3587109

The AP I got did not have a tube, not a heavy rod for the Cap Hat, but four rods with an eye on the end of each, thin, at most 3/16", but not 1/4" diameter.

 

[Marconi]

IM not trying to steer anything eddie, im hoping to minimise mast currents that could spoil the pattern,

the patent claims the pattern can be tilted 10-15 degrees below the horizon by removing the flare ,
i don't know if there is any truth in the claim, its not my idea,
its in the patent,

all im expecting from the astroplane is 1/2wave performance with a 4ft in height advantage of current maxima over other antennas mounted at the same tip height,
that could be an advantage at this location.

This sounds good to me Bob.

When you say removing the flare, do you mean to make the radials straight down to the hoop and making the hoop smaller to connect to the bottom end of each radial?

Or, are you suggesting that the radials should just be straightened out down to the hoop and the loop remains the same diameter?

As I understand things Bob, antennas are technically reciprocal, but it is also likely that TX and RX are different somehow. Maybe I just misunderstand what reciprocal meant in this case, and that is not the way this characteristic is measured.

It is very possible that all of my RX signal reports are faulty for this reason, but then I would have to assume that all the test reports I've seen for years were faulty too. What do you do to fix this? Don't you depend on a signal report from another to give you your TX signal reading from the other end? Doesn't that them make his report back to you the same thing as I'm doing?

I don't get it.

 

[Marconi]

Orion industries/Avanti patent filed 1968, published 1971
Read this one to find the referenced choke, 1/4 wavelength mast out the bottom. It's in there.

http://www.google.com/patents/US3587109

The AP I got did not have a tube, not a heavy rod for the Cap Hat, but four rods with an eye on the end of each, thin, at most 3/16", but not 1/4" diameter.

What do you mean when you say your AP did not have a tube?

I suspect the four rods you describe are the same rods that Avanti used on other antennas including the Moonraker. They are .125" x 24" inches of stainless wire.

I'll read the abstract again and see if I can find the part of which you speak of a choke. I don't doubt the antenna mast should be at least a 1/2 wave long and that would make it extend out the bottom of the hoop about another 1/4 wavelength. My only issue with your measurement was that I thought you told us, "...the part on your AP, below the hoop, was 108" inches." If that is the case, then the radials would have to be about that long too if the Patent is right.

You must of had a modified A/P. The fact that your antenna was also all 1/2" inch elements would suggest that it was going to be longer. I have two or three Old Top Ones and they are different too.

Homer, I was just trying to explain how difficult it is to get accurate measurements. I have my own antennas to measure, and I've found times when I still made a measurement mistake. I did not think I ever had good measurements for the Original Avanti A/P, and that is why I asked Bob to measure his and get me the dimensions...before he put his up.