I don't know. I figure it is because of it being isolated from, but adjacent to the top of the short radial side.
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Any Astro Plane Fans ?
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I was just kidding Homer.
The only reason I know of, as to why DB's model even has two wires at this point on the 6" inch mounting bracket instead of one is because he has to connect the mast to the model...and Nec only allows us to connect wires at the ends of other wire.
I doubt seriously we can make the A/P bracket non-conductive and still work effectively.
The only reason I know of, as to why DB's model even has two wires at this point on the 6" inch mounting bracket instead of one is because he has to connect the mast to the model...and Nec only allows us to connect wires at the ends of other wire.
I doubt seriously we can make the A/P bracket non-conductive and still work effectively.
Either way, I figured the portion of the bracket from the mast to the long radial would have to remain conductive. That part remained a dark color, not light blue.
I am just waiting on any other discussion about the AP because no matter the conversation so far the model continues to show the mast connection being driven against the short skirt radial connection. Everytime I've ever built a 5/8 GP the radials were driven against the upper vertical via a tapped inductor, or an inductor dimensionally equal to the tapped one. Looking at the simple mechanics of the odd shaped AP . . .
The bracket must be conductive in order to utilize the tophat 1/4 wave as the top 1/2 of the (folded 3/4 wave) half-wave dipole.
Nice read. I just bought another avanti astroplane AV-101, not even the AV-101A.
I ran one for years 1976ish to 1983ish. Was always my best omni. It talked way better than my Starduster, Radio Shack 1/2 wave and my big-stick, and ran neck in neck with the sigma 5/8 (and the sigma was huge)
So have we come to any conclusion as to isolate the mast below bottom of the radial or not?
I ran one for years 1976ish to 1983ish. Was always my best omni. It talked way better than my Starduster, Radio Shack 1/2 wave and my big-stick, and ran neck in neck with the sigma 5/8 (and the sigma was huge)
So have we come to any conclusion as to isolate the mast below bottom of the radial or not?
According to modeling, you need a certain length of mast, the patent does say a half wavelength and modeling would support this. For the most part, once you get to that length, most lengths longer than that work fine.
The DB
The DB
Hi,
i have a question about the Astroplane. There are two versions with and without the hat. What is the difference in practice? How long ist the tip without the hat?
73 Victor.
i have a question about the Astroplane. There are two versions with and without the hat. What is the difference in practice? How long ist the tip without the hat?
73 Victor.
I do not claim to be a expert on the Astroplane, But from what I remember and what I have read about the astroplane.
Avanti built 3 versions of the Astoplane and one Astrobeam: (US patent #3587109)
Concept (1970):
Did not have the cap and was claimed to be a 3/4 wave. This never became a production model and as far as I can tell and was never patented either that I have found.
AV-101 (1971-1978): $29.95
First production model, sold as a 5/8 wave with the cap.
AV-101A (1979-until out of business):
Second production model, as I have never seen one and can find little documentation I cannot list what was changed, it is still listed as a 5/8 wave and has the cap.
Note: I cannot find the box picture of the 101A, this one sold on ebay.
http://www.ebay.it/itm/Vtg-Estate-F...-HAM-RADIO-BASE-ANTENNA-AV-101-A/331492718469
AstroBeam
AV-150 (1971-until out of business) $59.95
The Astrobeam Had no cap
Sirio built 2 models of the AstroPlane, called the "Top One".
I have never seen one and know nothing about them or their build quality.
(maybe someone can fill in this blank.)
CB27 also made a version of the Astroplane called the"BA-27 Apache"
It also has the cap, but not the same bottom...
Avanti built 3 versions of the Astoplane and one Astrobeam: (US patent #3587109)
Concept (1970):
Did not have the cap and was claimed to be a 3/4 wave. This never became a production model and as far as I can tell and was never patented either that I have found.
AV-101 (1971-1978): $29.95
First production model, sold as a 5/8 wave with the cap.
AV-101A (1979-until out of business):
Second production model, as I have never seen one and can find little documentation I cannot list what was changed, it is still listed as a 5/8 wave and has the cap.
Note: I cannot find the box picture of the 101A, this one sold on ebay.
http://www.ebay.it/itm/Vtg-Estate-F...-HAM-RADIO-BASE-ANTENNA-AV-101-A/331492718469
AstroBeam
AV-150 (1971-until out of business) $59.95
The Astrobeam Had no cap
Sirio built 2 models of the AstroPlane, called the "Top One".
I have never seen one and know nothing about them or their build quality.
(maybe someone can fill in this blank.)
CB27 also made a version of the Astroplane called the"BA-27 Apache"
It also has the cap, but not the same bottom...
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The AstroBeam used a full length radiator element as the top radiator in the A/P dirven element, but it was very short, like 77" inches...as best I can tell based from the manual. Avanti added a short coaxial tuning stub for matching the AstroBeam. I'm not sure why they chose to do it that way...when they probably could have made the radiator a few inches longer to take care of the added capacitance like I did with my real world A/P.
If I knew the length and design of this stub...I might try modeling it to my AstroBeam model and see if there was something that Avanti knew at that time...making the pattern or the antenna perform better.
If anybody knows the length and the coax used...please let me know.
I modified my Old Top One from Coppers to a full 1/4 wave radiator. I got it to tune at 27.205 MHz using about 88" inches of tubing. I used the regular 46" x .75" inches shortened radiator element removing the top hat wires. I added 1/2" inch tubing above making the radiator 88" inches overall. I used a couple of stainless steel hose clamps to attach the top and bottom elements side by side with about 2" inches of overlap on the 1/2" inch tube. It worked fine...although not the best construction.
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Not one of your more informative posts...?
...and I'm not aware they ever made an Astro Plane without .a top hat ("cap")
People have experimented with the AP not having the cap hat, but the true AP has it.
I personally do not view the New Top one, nor Top One as either of them are Astroplanes. They are more like the Merlin to me.
To answer the question, as I understand it, the cap hat on the top provides for two essential functions of the antenna, shortening its length, and raising the radiation maxima to nearer the upper end of the antenna. To the extent that it does this is lost when the cap hat is removed. The upper vertical has to be lengthened to bring the antenna to resonance which defeats the ideas behind that part of the design.
I made a homebrew NTO, which seemed to work just fine, but was not fond of it. Why? It lacks the charm of the quirky looking AP, and it wasn't true to the design. It requires a gamma match add-on to effect tuning. Definitely not an Astroplane.
I personally do not view the New Top one, nor Top One as either of them are Astroplanes. They are more like the Merlin to me.
To answer the question, as I understand it, the cap hat on the top provides for two essential functions of the antenna, shortening its length, and raising the radiation maxima to nearer the upper end of the antenna. To the extent that it does this is lost when the cap hat is removed. The upper vertical has to be lengthened to bring the antenna to resonance which defeats the ideas behind that part of the design.
I made a homebrew NTO, which seemed to work just fine, but was not fond of it. Why? It lacks the charm of the quirky looking AP, and it wasn't true to the design. It requires a gamma match add-on to effect tuning. Definitely not an Astroplane.
Not one of your more informative posts...?
...and I'm not aware they ever made an Astro Plane without .a top hat ("cap")
I woke up in a daze and I thought I made a post without any commenst, but on looking back I could not find it...so I think I started a new post.
That's OK, with these holidays I've been in a daze for days.I woke up in a daze and I thought I made a post without any commenst, but on looking back I could not find it...so I think I started a new post.
