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.
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ASTROPLANE best vertical antenna ever?
- Thread starter nosepc
- Start date
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?
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.
Again, when I removed the wire, I didn't have to extend the mast.
According to the patent...
Astroplane Patent said:
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.
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.
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
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
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
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.
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.
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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.
What is it is definitely open for debate.
Something like...
If I got it wrong let me know.
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.
Glad to be of help.
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
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.
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.
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.
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.
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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.
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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.
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