Any Astro Plane Fans ?

[HomerBB]

I tend to agree with the assessment of the original AP that it is a 1/2 wave with the tuning portion doubling as a radiator. And so far, my experience with it is that it out performs other 1/2^ antennas of typical design.

 

[Marconi]

no eddie, i won't be setting up the nto with a full size 1/4wave, we know what the hat does with regards bandwidth and height of current maxima,

Bob, I know the current max will be a little different between the shortened radiator and a full length 1/4 wave, and the patent says the top hat version will raise the signal pattern above that of prior art antennas...whatever in the heck that is supposed to mean.

Do you have any ideas what "raise the signal pattern" means?

Can you tell me what I'm supposed to know about the differences in bandwidth between these two?

I accept that my tests were somewhat flawed, but they don't indicate much RX signal differences. I don't recall seeing much of a difference in just working my radio, and I only see a small difference in favor in bandwidth for the full length radiator with my bandwidth curve reports. Again a difference, but a small difference.

 

[The DB]

Hey Bob, wouldn't your topsy turvy design simply be a starduster with a collinear section?


The DB

 

[Marconi]

You may be correct about it being it not special after the isolation of coax and mast. However, I believe the antenna will be all it was designed to be when the mast is isolated the exact distance down from the loop as the twin top bracket is above the loop and the coax is choked at that same point. This is the stated design parameters of Orion/Avanti in the patent submitted in 1968 and published in 1971 that I linked above.

Of course I agree the A/P works great, but I hope the A/P does not change its strips if the CMC are effectively eliminated. That was just an idea I got thinking about how it looks to work, but I'm not sure. I think if I look back...I will find that free space models will show me the A/P shows almost exactly what I see with a center fed 1/2 wave dipole at the same height, maybe 2.14 dbi.

The idea that if we put the A/P up high somehow and compare performance with the mast out the bottom a full 1/4 wave vs one that is shorter will show some tilt down has me intrigued.

Right now I think I will only see a change if this bottom end it less that 4' feet from the hoop maybe, but as I sit here I can't say for sure. I did test this idea with modeling, and I think I saw something happen dramatic only when the antenna was mounted at 4' feet or less from the Earth, but again I'm not sure.

I think I was doing too many iterations the other day to keep it all straight in my thinking.

BTW, the other day you commented that the A/P Patent spoke about a choke on the feed line or mast as you note is indicated in Fig 5 & 6. I don't find it, so could you be more specific as to where these words are? My copy of the Patent is in columns and it has line numbers indicated as reference points.

 

[Marconi]

I tend to agree with the assessment of the original AP that it is a 1/2 wave with the tuning portion doubling as a radiator. And so far, my experience with it is that it out performs other 1/2^ antennas of typical design.

Homer, did you isolate and choke your A/P or the one you made? If so, are you saying you fixed the problem with the addition of the insulator and choke...or did you add them just as a mater of fact?

I think you told us that you did not notice any TVI, and that you isolated your antenna close to the base, but I would like to know for sure, if you had a problem and this fixed the problem.

 

[Marconi]

Homer, did you isolate and choke your A/P or the one you made? If so, are you saying you fixed the problem with the addition of the insulator and choke...or did you add them just as a mater of fact?I think you've told me in the past that you choke all of your antennas...and maybe you isolate them too, just in case.

I think you told us that you did not notice any TVI, and that you isolated your antenna close to the base, but I would like to know for sure, if you had a problem and this fixed the problem.

 

[Shockwave]

On an side note...Sirio no longer publishes this antenna and it looks to be out of production. I emailed them asking if this was true, but like Donald has said...they won't talk to me, because I ask them the questions they can't answer.

Marconi, I have resisted commenting on another complex Avanti antenna to see the views others have. I have been reading and would appreciate if you feel the need to quote me, please follow through without substituting your response for my own. Many of us recall the exchanges you had with Sirio that you posted here. I'm not the only one who noticed they were responsive to you right up until the point it became clear the problem was not that you misunderstood them but that you did not believe what you were being told. As your questions made this apparent you noticed the lack of response.

 

[HomerBB]

I always choke an antenna unless it is up for a temporary short time test basis. Sometimes I choke these also.

I always choke the coax on an AP style antenna at 9' below the loop. This is because the idea came up long ago in a discussion about this antenna.

I have not isolated the AP a 1/4 wavelength below the loop, but I have done so much farther down the mast. It was just a mounting coincidence.

The place in the patent version I am reading regarding the use of the choke is here:

. . . In other tests of the same installation, but with shorter mast lengths of . . . (less than one quarter wavelength) . . . it was found that the radiation angle at maximum beam strength tilted upwardly substantially more. The conclusion to be drawn, therefore, was that a mast having a length below level B (the loop) of about one-quarter wavelength, i.e., about the length of the conductors I6, 18 gave an optimum takeoff angle.
Of course, as explained, coaxial cable feed connections 38 and 40 are made to the clamp assembly and to the split brass ring and the cable 37 itself is suitably taped to the mast. It has been found that when an outer braided conductor forms the cover of the coaxial cable, this may serve as the first conductor. In such a case, the conductive mast 14 may be omitted and a nonconductive support substituted therefore. When that is done, it is important to make certain that the coaxial cable is positioned and centered properly with respect to the other conductor members described.

The text does not state explicitly that there is either a choke or isolation or both, but states the conclusion from the design and testing of the AP that a mast of no longer or shorter than 1/4 wavelength below the loop yields the optimum performance for the AP, or a non-conducting mast with the coax braid acting as the conducting mast may be used in the same way.

THEREFORE, the nature of RF being that it will locate a CMC path of opportunity tells us there should be isolation of one quarter wavelength of the conducting mast and conducting coax braid.

US Patent # 3587109

 

[Marconi]

The place in the patent version I am reading regarding the use of the choke is here:

The text does not state explicitly that there is either a choke or isolation or both, but states the conclusion from the design and testing of the AP that a mast of no longer or shorter than 1/4 wavelength below the loop yields the optimum performance for the AP, or a non-conducting mast with the coax braid acting as the conducting mast may be used in the same way.

Homer, I see your point now. But, I read a similar comment in the Patent where a similar mention of the topic uses the words below to describe how long the mast #14 should be for maximum signal strength to optimized for such as CB use and the like, instead of your reading.

Stated another way, the first conductor #14 should preferably project beyond level B a distance at least equal to about the length of conductors #16 & #18.

The PDF file below shows the text for both comments in the Patent and I noted the location for each. Our references are both the same text Homer...just the formats are different.

I will go back and see what my results were when I tried making the 16' foot mast I used inside and sticking out below the mast (I call the antenna mast) on a A/P raised up higher that mounting on the ground. I still think this shortening of the antenna mast only shows noticeable tilt up when the antenna is ground mounted...not raised up, but we will see what Eznec predicts.

So, I don't think the length of the mast makes much difference regarding this claim unless the mast it shorter that maybe 4' or 8' feet to the ground.

 

[Marconi]

Here is a comment from gamegetter that I read somewhere that suggest my thinking on the subject about how high Avanti might have been considering in the writing about the testing of their AstroPlane in the Patent. IMO mounting antennas low to the ground might have been pretty common in those days.

both would be interesting for the direct radiation pattern and image reflected by the ground, but i don't want to trouble you if it is alot, just don't like to leave any stones unturned by guessing what the pattern and reflection might do.

it would be interesting to see what they were seeing back then when they modeled it in the early 70's as they expected a low ground install versus what one would see today if installed as high as possible.

good day.


#31

gamegetter, Apr 27, 2012

 

[Marconi]

Marconi, I have resisted commenting on another complex Avanti antenna to see the views others have. I have been reading and would appreciate if you feel the need to quote me, please follow through without substituting your response for my own. Many of us recall the exchanges you had with Sirio that you posted here. I'm not the only one who noticed they were responsive to you right up until the point it became clear the problem was not that you misunderstood them but that you did not believe what you were being told. As your questions made this apparent you noticed the lack of response.

You are the one that made the insulting comments about a post I made regarding my not getting a response to a question I emailed asking if the AstroPlane was still being manufactured. I also emailed asking how the gain for the New Vector 4000 was reported...in Free Space or over Real Earth and I got the same no-response.

I just stated the facts Donald.

 

[bob85]

The spacing is whatever you can stretch a 1/2wave delay to eddie,
you could use
a 1/4wave transmission-line stub, like the super j-pole

hoops or coils, like the BIG-MAC

stretched coil, like the co-linear j-pole

Franklin uniform

other folded phasing,

no coax phasing lines, the stub brings the upper 1/2wave into phase with the lower 1/2wave gamma fed dipole,

if the idea can give some gain at low angles compared to the stock vector4000 without increasing antenna height its worth testing.

i can't tell you exact dimensions Eddie,
the lengths would have to be adjusted for best performance, adding the stub and extra 1/2wave will effect the tuning of the lower dipole.

 

[Shockwave]

You are the one that made the insulting comments about a post I made regarding my not getting a response to a question I emailed asking if the AstroPlane was still being manufactured. I also emailed asking how the gain for the New Vector 4000 was reported...in Free Space or over Real Earth and I got the same no-response.

I just stated the facts Donald.

I didn't think is was so insulting to point out that they were responding to you until you keep asking the same question different ways as though you were going to get different answers. There is no difference between an antenna that has 2db over a dipole in free space or one that has 2db over a dipole placed over real ground. The key here was the "D" at the end of dbd that indicates the reference is a dipole.

The very people who built the model and new Vector had also been reading the posts here on the antenna and were going to join as a member to participate. After seeing the "endless debate" they decided to do the same thing Cebik did and resist controversy.

 

[Marconi]

I didn't think is was so insulting to point out that they were responding to you until you keep asking the same question different ways as though you were going to get different answers. There is no difference between an antenna that has 2db over a dipole in free space or one that has 2db over a dipole placed over real ground. The key here was the "D" at the end of dbd that indicates the reference is a dipole.

The very people who built the model and new Vector had also been reading the posts here on the antenna and were going to join as a member to participate. After seeing the "endless debate" they decided to do the same thing Cebik did and resist controversy.

Just more BS Donald. Why don't you tell the truth for a change.

 

[Marconi]

The spacing is whatever you can stretch a 1/2wave delay to eddie,
you could use
a 1/4wave transmission-line stub, like the super j-pole

hoops or coils, like the BIG-MAC

stretched coil, like the co-linear j-pole

Franklin uniform

other folded phasing,

no coax phasing lines, the stub brings the upper 1/2wave into phase with the lower 1/2wave gamma fed dipole,

if the idea can give some gain at low angles compared to the stock vector4000 without increasing antenna height its worth testing.

i can't tell you exact dimensions Eddie,
the lengths would have to be adjusted for best performance, adding the stub and extra 1/2wave will effect the tuning of the lower dipole.

You could tell or show me what you imagine, instead of asking me to imagine what you are thinking Bob. Like I said I think the first design might work if the dimensions are right...but I have my doubts the other model on the bottom will work unless the top element is connected to the antenna system somehow. It might be possible the RF from the bottom might passively radiate the top element...but I doubt it would be worth while.

I'm not the expert go-to collinear or phase-o-magic guy, apparent or non-apparent...on the forum.