ASTROPLANE best vertical antenna ever?

bob85 said:

Eddie
The first image looks like you put the choke at the wrong side of the feed-point to my eyes, is that what you did ?

The other images are too small to see whats going on.

Click to expand...

No, I put the choke on the right hand side of the feed line as close to the Feed Point as I could get it. If I had placed the choke on the left hand (other) side of the Feed Point, that might happen if the coax was running down the mast. I should have turned the currents off in this model...maybe the red lines for currents are confusing this image.

Bob, try using the Zoom (+ -) feature that is at the top of the PDF images. On my end I can zoom-in up to 600% or more. The image gets a little pixelated, but it's not that bad. I have asked folks before to tell me if they see this PDF Tools on their end of the post I've made, but no one as ever answered...so I'm not sure what you guy's see on your end. I sure don't know what others using a cell phone are able to see with PDF files either.

Sorry, the other two images only gave me some full image size in the Landscape view, or else the images would be split between two pages in the portrait view. Maybe the best solution would be to print the images if you had to see without bending your head over a little. You can also use Zoom here as well to help see better.

Eddie,
I can zoom 650% or more but i can't see what i think you can see,
first image is fine, the other two i can't see good enough,

i don't have a printer anymore, i use them so infrequently that i end up needing new cartridges most times i come to print something so i gave them to friends who wanted A3 printers.

Bob I'm not sure, but I seem to recall sometime back that PDF files looked much sharper and with a lot more color. I don't know if this has to do with me using Windows 10 now vs. when in the past I used Vista. Every thing on my old Vista computer still looks better and now I've received word that AV software will shortly no longer provide protection anymore for Vista. Planned obsolescence.

These two images you can't see well...just show the error I made in the data I put into the Transmission Line Tool. The error basically made the coax unconnected from the model. I described this earlier...as though I put my antenna up and forgot to attach the coax.

Remember I was working with an A/P model that had no mast at all, and I wasn't satisfied that I could tune the idea without a mast...until I was able to add a feed line and see if the model still worked. That is when I made the error, so I did not see the effects you brought to my attention. If it were not for your collaboration in this case a lot of folks could have been misguided and I would not have likely question the results either.

You mentioned the fact I talked about Loosecannon wanting to put up his CTE Old Top One, an A/P knockoff, and use the feed line as the path to ground. You may be right about that not working due to the small metal content or diameter in the coax shield used in his idea. He was going to test the idea, but ?????

IMO, this is what us talking about such things among a few others is all about. Sometimes we make mistakes, and realizing mistakes can also be important to learn about...so we can be more watchful and maybe gain some better understanding.

Unfortunately there does not seem to be very much interests anymore...except maybe from a few old die-hards.

Thank you Bob and DB.

Marconi said:

Unfortunately there does not seem to be very much interests anymore...except maybe from a few old die-hards.

Thank you Bob and DB.

Click to expand...

I think there is more going on with this antenna than many (in fact most) people realize. There are things I've seen happen with models of this antenna that I haven't seen happen with any other antenna model, and those things were consistent across multiple different models of this antenna that I have made over the years. In my opinion it is a very interesting antenna, and in the past when I had a chance to play with said models I think I have learned more about antenna theory from modeling this antenna than any other antenna model I have looked at, with the possible exception of the Sigma 4/Vector 4000.

I just wish I had more time to play with said models right now while said discussion is happening...

And I just noticed that this thread earned a sticky...


The DB

Eddie,
i stood my astroplane on a 45 gallon plastic drum open end up suspended on 2 fiberglass pole sections to put as much air around the hoop as i could for a quick check with the coax hung down where the mast should be,
i don't remember the vswr but it was not very low as it is with the mast,

my astroplane is tuned spot on for your band with a 1.5" mast when its clear of stuff around it, with a smaller diameter mast vswr is a little higher in my test,

homer may have more info since he's built a few Macgyver astroplanes with none conventional construction & got a decent vswr.


DB
do you have time to make an open sleeve antenna model with 1/2wave monopole & 1/4wave sleeve elements to see if you get a same or similar odd current distribution on the monopole with less current above the sleeve elements when all 3 elements are resonant

what you describe as a 1/4wave current distribution on a 1/2wave conductor,
if you do that could be a good starting point to figure out part of what's going on with the astroplane.

Bob, did I hear you and DB talking about current distributions?

You probably won't be able to read the currents image, but I think this is what Roy was telling me on the phone at some point, "...keep you eyes of the Tabular Current Log data...if you see currents that are not distributed evenly...you likely have a problem with the model."

IM not sure Eddie,

with regular antennas such as ground-planes dipoles you don't have any transmission-lines in their construction I would expect to see the usual current distribution on all wires,

1/4wave high at one end low at the other,
1/2wave low at each end high in the middle,

if I was not getting what I expect I would suspect an error,

but I believe there are antennas out there that won't have the expected distribution on a conductor such as a 1/2wave monopole with 1/4wave sleeve elements brought to resonance,
i don't know what that looks like in NEC but i would like to see it,

everything about the astroplanes sleeve screams maximum unbalance & minimum mast current from its 1/2wave mast to its flared for wider spacing at the end of the sleeve,

it also causes the end of the sleeve to be looking at air while the central monopole is looking at the low end impedance of a 1/4wave rather than the high end impedance of a 1/2wave as it would be if the monopole was extended to 3/4wave like j-poles & ssfm, giving a much more unbalanced situation than a j-pole ssfm,

unbalanced lines radiate,,

I can't build a model of a 1/2wave open sleeve with 1/4wave sleeve elements to see if it gives a similar effect to what DB is seeing in his 1/2wave astroplane mast models

I think the co-inductive could be a combination of current modes within the same antenna,
not just a sleeve monopole I described earlier because its clearly not just an open sleeve monopole,

it also looks like the hot side transmission-line is driving the cold side transmission-line line which looks like a 1/2wave end fed because the bracket shorting the cold side is invisible when its transformed through a 1/4wave tapered line,

IS it a funky folded j-pole / sleeve monopole hybrid With two current modes two radiating currents making it difficult to understand unless your a Cebik or maxwell kind of guy.

will we ever understand whats really going on with this antenna ?

Here is an Avanti link that I don't recall ever seeing before. Co-Inductive is discussed at the top.

https://worldradiohistory.com/Archive-CB-Radio/Catalogs/Avanti-CB-Antenna-Catalog.pdf

Eddie
They are saying the astroplane without the uper 1/4wave creates an intense electric field,
& that short upper monopoles carry little current until you approach 1/4wavelength,

id say that short monopoles & masts in general have high end impedance & low current,
when you lengthen them towards 1/4wave end impedance goes down & current is maximised,
does not matter if its on top of an astroplane or under an antenna acting as a mast.

everything about astroplanes seems to maximise what you would normally try to suppress in other antennas that are not upside down like the astroplane,

the last thing you want on a j-pole or ssfm is a 1/4wave isolated mast to carry high common mode current,
but it is what you want if you want it to carry high current & radiate,

Eddie,
i don't pay any attention nowadays to what makers claim for gain,
EZNEC & other MOM sofware blew a hole in their nonesense years ago,
tests confirm it,
noise is EVERYTHING for many urban dwellers, i hear more than locals because i have the least noise.

i don't know what they mean by Co-inductive but there are two currents in that antenna,
maybe they meant co-mmonmode .

bob85 said:

i don't know what they mean by Co-inductive but there are two currents in that antenna,
maybe they meant co-mmonmode .

Click to expand...

I read this definition somewhere, a Colinear antenna, not Collinear, has two elements connected with 2 straight lines, like a dipole or a ground plane antenna.

At some point later on I remember the HyGain CLR2 being referred to as "...an extended 1/2 wave antenna." I guess these words "extended and 1/2 wave" were not scientific sounding enough, for the CB world back then, because again and later-on the description "Colinear' popped up in their ads. I think this may be what CLR stands for, "Co Linear Radiator."

So, maybe Avanti glamed-on-to their idea to make their company brand logo, "Co-Inductive." It sounds scientific, mysterious, and different. And IMO, they were scientific, mysterious, and different.

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Bob, this may be why it seems to be an uphill battle trying to figure out the A/P design and the minutiae in details.

I think Avanti, practiced an art philosophy that maybe they claimed in their patent at column 4, lines 26 - 29.

A construction wherein points c and d are electrically coupled, but where the circuitry is otherwise similar, will produce a similar result, i.e., a closed conductive loop may also be used.

Click to expand...

I'm gonna' stop...I may just be rambling here.

Eddie,

as far i i am aware there are only two possible modes that current is flowing in the astroplane IA & IT
the two modes i have talked about,

all regular antennas i know of use antenna mode with the usual distribution curves
apart from antennas with transmission-lines within their construction such as j-poles & sleeve monopoles which use both modes,

you don't see that in NEC but you do see the resultant radiation due to unbalance in the stub that is caused by the mode you can't see,

it may not look like a sleeve monopole but it has to have the same currents when it has parallel conductors in close proximity that lower feedpoint impedance,

i think many folk don't understand a simple j-pole,

look at this vid explaining how a j-pole works,


its incorrect & theres nothing complicated about j-poles once you read Cebik's articles like "some j-poles that i have known" or any info on what makes transmission-lines radiate,

that mast does effect the antenna, it will carry common mode,
any conductor with a voltage differential between any two points on the conductor will radiate,

the balanced line is not balanced as he claims even before he attaches the unbalanced coax,

the top of the stub is unbalanced because one side sees the near infinite impedance of air while the opposite conductor sees the lower end impedance of a 1/2wave monopole,

which unbalances the line & causes the short leg to radiate giving the lobsided pattern with more a bit more gain in the direction of the short leg,

the wider the space at the top of the stub the more unbalanced it is which increases radiation from the short leg,

imho taper allows the same characteristic impedance for the transmission-line with increased unbalance at the top of the stub, ( i could be wrong )

i looked back in time to Heavisides work on electromagnetic wave propagation along the external region of transmission lines, tapered transmission-lines, charactersistic / surge impedance,

too complex for my old head but theres some usefull info for anybody interested enough to look at it.

look at just a couple of things that unbalance a balanced line causing it to radiate then look at the astroplane,

a balanced line will be unbalanced if you terminate the far end with an unbalanced load such as seen in the j-pole & ssfm,

3/4wave monopoles give best balance, most current on the monopole, least radiation from the sleeve, it does radiate but not a lot,

1/2wave monopoles give the worst balance, least current above the sleeve elements & high radiation from the sleeve ,

the wider the spacing at the top of the stub the more unbalanced it will be,

a balanced line will radiate if you flare or taper the conductor so they are not perfectly parallel as seen in henry's terminated sigma4 cone model,

a balanced line will radiate if you feed it asymetrically,
ie not directly central between the parallel conductors, if you offset your source you will see some radiation,,

now look at masts not connected to ground,

1/2wave masts have high end impedance low current,
1/4wave masts give low end impedance high current just like a 1/4wave whip or the legs of your 1/2wave dipole,

so how would you maximise radiation from the sleeve and the upper monopole of the astroplane while minimising current in the mast below the sleeve elements?

I think you would

use a 1/4wave upper monopole,
use isolated 1/2wave mast,
choke the coax at the end of the mast 1/4wave below the hoop,
make the space at the hoop as wide as practical for maximum unbalance while still maintaing the correct transmissionline impedance for low vswr by flaring the lines.

what would i avoid,
i would avoid odd 1/4wave masts that screw with vswr & cause the mast to carry significant antenna mode current .

IF thats not what is going on or at least most of whats going on with an astroplane i will eat my hat.

I better find the salt, hats taste like shit.