Buying An Astroplane

[CDX-007]

Homer, how much lower, if at all, is the top of the AP than was the top of the 5/8λ?

1.5' lower top to top AP to 5/8

AP - 54.4'
5/8 - 56'

Close enough.

Same results I got many decades ago when, as a teen, I compared every antenna I could get my hands on and found the Hy-gain Penetrator.64, Taylor GLR-4.64, Wilson AlphaV5/8 & Avanti Sigma5/8 outperformed all others, including the Starduster & Astroplane, when mounted atop my 45' mast over the then 12' high roof, 57' to the mast top.

I never even thought about adding another section to the 5 section mast to 'even things up a bit'. I just figured you buy an antenna, install it on the highset mast available and let it do it's thing, ...and may the best performer win.

 

[HomerBB]

Close enough.

Same results I got many decades ago when, as a teen, I compared every antenna I could get my hands on and found the Hy-gain Penetrator.64, Taylor GLR-4.64, Wilson AlphaV5/8 & Avanti Sigma5/8 outperformed all others, including the Starduster & Astroplane, when mounted atop my 45' mast over the then 12' high roof, 57' to the mast top.
.

When I said this:

"So far the AP seems to do as well in terms of the clarity of the audio. What seems different is the S-units are down on the local signals. I know S-units are not proof positive of things given the variety in radios, but this is exactly the same everything, radio included."

I think I would have said it better had I said the clearer sounding audio was because it seemed to be louder. I think this is due to the fact that I have less white noise with the AP so that the audio stands out and is more readily understood, particularly to stations 10 - 20 or 30 miles out. Very close in local stuff is quite clear and loud, and the S-units are lower than the 5/8. Perhaps this is because all of the AP is higher than the longer antennas? I can't definitively say so . . .

 

[Marconi]

Hey Marconi, I just got to reading that, now I'm wondering how long you needed to make the top tube when you tried the AP without top hat radials? How was it's performance compared to stock configuration?

As per the following Antenna Work Sheet reports, I made three iterations to get my AP resonant at 27.205. Started with a full 1/4 wavelength of 79.5".

Report #1, using the 1/2" x 45" tip element from my Sigma4, the report shows I was short and high in frequency up near 27.605 mhz.

Report #2 shows I then went to 89.75" length, and the VA1 showed I was about 8 channels low at 27.105 mhz. That was fine considering the antenna is so broadbanded, but it wasn't where I wanted it.

Report #3 shows I changed the length to 87.5" using the same 5/8" element on the Top One and hose clamped the Sigma4 tip element to its side. The VA1 then showed a very nice dip at 27.205, but the data recorded after that also was skewed...as you will note on the report. This sometimes happened, I think, when someone in the area of my station keyed up some big-time RF. You'll see that the RF did not seem to affect the SWR inline meter scan that I did soon after the VA1 scan. Also I noted later, when I rehashed the reports, that I made an error in the final adjustment or I recorded the info wrong. I made an error that looks like about 1", so I'm not too sure what the actual top element length really was. It had to be close to 87.5" however to make my Top One center at 27.205 with a straight full length 1/4 wave top element.

Based on the report dates and other reports of the time, I had this full 1/4 wave TO configuration up only a few days. I do have two reports #13 &#14 dated 08/1/09 for the AP vs. Sigma4 showing the Sigma4 besting the AP by .9 Sunit on average, but the reports around that time were random reports only and were not even close to showing the reliable differences I was expecting...even if it's not possible to make reliable signal reports.

Based on the fact that I took the thing down and fixed the TO back to its original top hat configuration suggest to me...that I didn't like the results of making the top a full 1/4 wavelength. I didn't even make notes. Soon after that I started remodeling my house and I stopped all testing. These Signal and Work Sheet reports are all posted in my albums. http://www.worldwidedx.com/members/marconi-albums-marconi-s-signal-reports-may-august-2009.html

View attachment AstroPlane Antenna Work Sheet 073109.pdf

Close enough.

Same results I got many decades ago when, as a teen, I compared every antenna I could get my hands on and found the Hy-gain Penetrator.64, Taylor GLR-4.64, Wilson AlphaV5/8 & Avanti Sigma5/8 outperformed all others, including the Starduster & Astroplane, when mounted atop my 45' mast over the then 12' high roof, 57' to the mast top.

I never even thought about adding another section to the 5 section mast to 'even things up a bit'. I just figured you buy an antenna, install it on the highest mast available and let it do it's thing, ...and may the best performer win.

You're right 007, when we're just installing antennas, but I like to think my comparison work is devoted to testing or comparing rather than the simple process of our CB buddy "Fried Chicken Livers" installing his new antenna his mommy got him for Christmas. I'm not telling anyone to follow my instructions, I'm just relating my limited experiences doing "what if" experiments. I became inst rested long ago when a buddy of mine had a Starduster and he talked to guys in the distance I could not copy. Even back in the late 70's guys complained that the SD and the AP, both very short antennas were junk, while Johnny talked all over with his Washington radio and SD antenna. Other guys heard this too and went out and bought these same antennas and installed them, but they put them on a 10' or maybe an 18' foot mast and they failed to be able to do what Johnny could do. So, they all talked bad about his little antenna. I discovered later that Johnny live in a very high two story garage apartment that was about 30' to the peak. He had two 10' sections of Schedule 40 conduit screwed together with a 50' foot pushup pole inside about 4' feet. His antenna was well above 60' and that made the difference folks were seeing. Johnny was notorious in the area and everyone figured he had a big amp, but Johnny only had a 80 watt modulator that talked like it was a 1000 watts. Of course if he had installed a big old Vector 4000, Penetrator, or an I-10K up there he likely would have done even better, but then he had to worry about the wind with such a flimsy install.

 

[Marconi]

When I said this:

"So far the AP seems to do as well in terms of the clarity of the audio. What seems different is the S-units are down on the local signals. I know S-units are not proof positive of things given the variety in radios, but this is exactly the same everything, radio included."

I think I would have said it better had I said the clearer sounding audio was because it seemed to be louder. I think this is due to the fact that I have less white noise with the AP so that the audio stands out and is more readily understood, particularly to stations 10 - 20 or 30 miles out. Very close in local stuff is quite clear and loud, and the S-units are lower than the 5/8. Perhaps this is because all of the AP is higher than the longer antennas? I can't definitively say so . . .

Homer if you'll look at the link for Signal Reports #12 & 13 in my post above, you'll see what I was seeing at the time with the Sigma4 and my TO with a full 1/4 wavelength radiator at two different relative heights. I don't think however that I made any effort to record anything but random signals, so what you see is probably not relative between reports even with my trying to make comparisons. There may be a couple of stations in common on these two, but I recall there was nothing controlled in the reports. So??????

Are you planning to make your AstroPlane with a full 1/4 wave tip? The last we heard from Starduster he was planning to make his homemade AstroPlane with a full 1/4 wave tip, but sadly he just disappeared.

 

[HomerBB]

I can do that with relative ease. Cranking the tower over and up again is a matter of minutes. However, I think I'll leave as is until I sit through several different radio sessions to try and record data rigorously. Likely, I'll try as you suggest.

Additionally, I read the report you did on it in April, 2006 at the link you gave me. I found it very interesting - informative. It seems to me that your then conclusion that it may have been a 5/8 antenna was presented as central to other conclusions. I'd find it interesting how you'd rewrite it with your newest point of view re 1/2 wave. Just a thought . . .

I'll look at your links on "...Signal Reports #12 & 13"

 

[Marconi]

I can do that with relative ease. Cranking the tower over and up again is a matter of minutes. However, I think I'll leave as is until I sit through several different radio sessions to try and record data rigorously. Likely, I'll try as you suggest.

Additionally, I read the report you did on it in April, 2006 at the link you gave me. I found it very interesting - informative. It seems to me that your then conclusion that it may have been a 5/8 antenna was presented as central to other conclusions. I'd find it interesting how you'd rewrite it with your newest point of view re 1/2 wave. Just a thought . . .

I'll look at your links on "...Signal Reports #12 & 13"

Well Homer, that site is controlled by FreeCell and only he is able to edit the report or I would have updated it. The only difference in my mind now is that I could never figure out how the bottom hoop worked electrically. As I said earlier, I reasoned the physical 1/4 wave loop may serve electrically as the bottom 1/8 wavelength of the traditional 5/8 wave radiator and thereby concluded the 5/8 wave idea. Personally, I don't believe that Avanti ever indicated the wavelength for the AstroPlane. Maybe some of the dealers or maybe some in the CB community started all that talk.

I think that Bob85 gave me a clue once about the hoop simply serving the antenna as a non-radiating connection from the bottom of the 1/4 wave tuner under the feed point to the other side of the antenna...where there is the voltage end of a 1/2 wave radiating element. If you will notice looking at the location of the feed point in the hub it is located at the center of the 1/2 wave antenna. Both of the 1/4 wave down projecting elements are bowed a bit in order to raise the feed point impedance. I think this idea is suggested in the Patent, plus Avanti also makes a brief discussion in the Patent regarding similar circuits with different construction producing similar results suggesting for me their idea that this was effectively a center fed antenna and I concluded it has to be a 1/2 wave due to the physical length.

The RF currents for the 1/4 wave tuner and the hoop are self canceling due to the same rule that governs cancellation inside of coax. Parallel lines with equal current magnitude but with the currents flowing in the opposite directions = cancellation.

If you look at the AP pattern noted in Avanti's Patent, you will notice a small lobe present on one null side of the two lobe pattern. It is between the lobes located at the base of one of the nulls. I consider this as evidence the pattern is a 1/2 wave radiator and that the little lobe represents the physical presence of the antenna structure to one side of the radiator, including the tuner, and the supporting mast. I also believe this issue is discussed in the Patent as well. See image below.

I hope I've used my words to be clear.

 

[HomerBB]

Thanks. It's perfectly clear. Amazingly so considering even a year ago I would have struggled to follow your thinking.

The curious thing for me is why this ring would only serve as a non-radiating connector while in the discussion of the V4k the ring's dimensions, tube thickness, diameter of the ring, circumference, position in respect to the length of the 4 radials, etc, was discussed as critical to the efficiency of the antenna leaving little doubt to its being included as a part of the radiating system. Perhaps I just assumed?

 

[Marconi]

Thanks. It's perfectly clear. Amazingly so considering even a year ago I would have struggled to follow your thinking.

The curious thing for me is why this ring would only serve as a non-radiating connector while in the discussion of the V4k the ring's dimensions, tube thickness, diameter of the ring, circumference, position in respect to the length of the 4 radials, etc, was discussed as critical to the efficiency of the antenna leaving little doubt to its being included as a part of the radiating system. Perhaps I just assumed?

I haven't thought about it, but it is a point to consider. Right off the bat the Vector/Sigma4 will work without the hoop, but the Astroplane won't work at all without the hoop. I think I recall your antenna would not work without the hoop too, but in that case I think you had other issues that you fixed later, and maybe after the fix it would have worked without a hoop like Avanti suggested in their Patent.

When I described the AstroPlane as a 5/8 wave, I use to consider the bottom hoop as part of the actual radiator. When Bob explained how the current might be flowing in that case, I saw cancellation in the hoop. I think in the Sigma4 the hoop has some affect on the phase reversing condition that helps make the design a collinear. Bob is the best one to talk to on this count.

I don't know if I'm right or not Homer, I'm not up on electrical stuff. I do change my mind sometimes, thinking I was wrong about some issue. Those guys at Avanti seemed able to use similar techniques in their designs...where they use cute little tricks, being able to create similar circuit responses with totally different configurations. I don't particularly like buzz words, but we might call this, "...thinking out of the box."

 

[HomerBB]

Thankfully my curiosity is not a challenge to anyone's thinking, esp yours. What I know is virtually zero. I just am wondering how/why such a significant amount of metal can be introduced, not near by, but within the very circuitry of an antenna and not be considered effective in terms of radiating RF. Clearly I am far below the standard of understanding I ought to be to even ask such a thing. However, admitting my ignorance, it has been my understanding that all matching systems carry RF, albeit, I admit, not necessarily in a way that emits RF in a way useful to TX/RX other than to affect the match - like a coil that produces current along the coil, but not necessarily around and around the coil (Lord have mercy, I know someone is going to come and work me over for my poor terminology, and weak science . . . please do). It's relationships, I know, like the curve in the skirt section of the AP affecting the match. BUT, this hoop is so large that it seems almost unbelievable that it isn't part of the radiating antenna in the sense that the vertical portions are. What contributes to the cancellation of its currents? the mast down the middle? :blink:

Maybe I need to read your article again.

Thanks, Marconi.

 

[HomerBB]

Quoting 007 talking to Marconi on the SGM thread:

I'd still like to see you try the .64 tuned I-10K . . .

I must say I've never seen anyone who so persistently wants to prove/disprove the merits of an antenna. I tell you what. When I get back to the 5/8 testing phase of this AP vs other antennas, I'll try to retune the antenna for .64 and do some data collection for you. I don't have any voodoo soil here, just plain old rock infested mountain dirt.

I am considering in my test now:
AP
5/8
V4k
.64
Quad Loop (maybe - because someone elsewhere mentioned it)
and if I can figure out the physical mechanics, a homebrew SGM.

 

[Marconi]

Thankfully my curiosity is not a challenge to anyone's thinking, esp yours. What I know is virtually zero. I just am wondering how/why such a significant amount of metal can be introduced, not near by, but within the very circuitry of an antenna and not be considered effective in terms of radiating RF. Clearly I am far below the standard of understanding I ought to be to even ask such a thing. However, admitting my ignorance, it has been my understanding that all matching systems carry RF, albeit, I admit, not necessarily in a way that emits RF in a way useful to TX/RX other than to affect the match - like a coil that produces current along the coil, but not necessarily around and around the coil (Lord have mercy, I know someone is going to come and work me over for my poor terminology, and weak science . . . please do). It's relationships, I know, like the curve in the skirt section of the AP affecting the match. BUT, this hoop is so large that it seems almost unbelievable that it isn't part of the radiating antenna in the sense that the vertical portions are. What contributes to the cancellation of its currents? the mast down the middle? :blink:

Maybe I need to read your article again.

Thanks, Marconi.

Homer this may be wrong, but it is the way my mind's eye sees the current flows in the AstroPlane. The 1/4 tuner under the feed point working against the mast showing currents flowing in the opposite directions, thus some cancellation.

The currents flowing in the orbital hoop are flowing a circle with all points on the circle showing the same impedance. On the tuner side of the tap point the current is going to the left in the image. At the opposite tap point, connecting the hoop to the 1/2 wave radiator, the currents are going toward the right in the image. Thus the currents are in affect going in the opposite directions. So, again we have some cancellation...leaving only an end fed 1/2 wave radiator with a shortened top element that has a top hat...doing the radiation just like a center fed 1/2 wave radiator.

I had to reduce the size of the paint image and it didn't turn out too clear, but maybe you can see enough to see my idea for how the currents might be flowing and where cancellation might occur.

I appreciate all comments that might clear this up, even if you disagree. I'm just looking for a good explanation, and my being right or wrong on the issue is not important.

 

[HomerBB]

Your image works just fine. I was able to key ctrl + + to get it a little larger.

So what I'm hearing is everything about the antenna is matching system - as if the short side of the skirt section is a large gamma? - with the exception of the center fed 1/2 from its connection point on the hoop up through the feedpoint at the top of the mast on upward to the top hat radials.
(of course, the photo shows the current flowing the opposite direction from the top hat downward, which seems odd given the feedpoint is in the middle, more or less)
I have no contradictions, just thoughts and questions.

I know what I'm saying may seem ridiculous to some, but I do invite one and all to help clear my muddled mind.

 

[Marconi]

Your image works just fine. I was able to key ctrl + + to get it a little larger.

So what I'm hearing is everything about the antenna is matching system - as if the short side of the skirt section is a large gamma? - with the exception of the center fed 1/2 from its connection point on the hoop up through the feedpoint at the top of the mast on upward to the top hat radials.
(of course, the photo shows the current flowing the opposite direction from the top hat downward, which seems odd given the feedpoint is in the middle, more or less)
I have no contradictions, just thoughts and questions.

I know what I'm saying may seem ridiculous to some, but I do invite one and all to help clear my muddled mind.

As I've said before, it seems that the guys at Avanti, like to make their matching schemes very large and parallel to the radiator. I believe this makes for a very smooth transition of AC energy to RF energy in the matching process...which IMP reduces any matching disturbances that might tend to alter the pattern.

Well Homer, I choose to show the current flowing in the still image I used...with the center current returning to the source and the current inside the shield flowing up toward the antenna. I believe such images are shown this way so we can show the outside of the shield currents flowing back toward the source when indicating Common Mode Currents and it all make sense. I am working on an animated version however, as we speak.

I'm reminded that with AC currents we can only depict one cycle for our images, so we have to choose a direction. In the real world the currents are alternating rapidly, and too fast to be seen in the millions of cycles per second. The direction of the arrows I added are only a snapshot at a split second in time. Sorry I didn't take the time to reposition the image below as an example of my madness, but you can go to the top of the page and rotate the image clockwise or counter clockwise.

View attachment IMG.pdf

 

[HomerBB]

I had a feeling the answer to the current arrows were as you said. Thanks. It makes sense even to me ( you might ought to be worried).

 

[CDX-007]

A Different Take on the AP

Now, I dunno...

because it seems to me like the AP would have to be either a ¼λ or ¾λ if it's going to offer a 50Ω impedance being directly driven.

...but then that would require a ¼λ counterpoise and it wasn't until you said something about "upside down antenna", Marconi, that I thought about the fact the shield is DC coupled through the bracket to the top ¼λ element which I believe could be doubling as both a radiator and a counterpoise, depending on the phase point in the cycle, and if the current travels the long path down around the ring and back up the other side.

So, when the current is high at the feed point, it's low ¼λ down & across the ring, high again at the mounting bracket (minimum voltage) and low again at the top of the top hat, so it would be basically a folded ¾λ but with the 1st ¼λ folded up to correct the phase.

The shield being 180° out of phase could couple to the top ¼λ element as a counterpoise since it's base (at the bracket) is 180° (½λ) out of phase from the feed point.

- Just a thought

Will the AP still tune & work correctly if ½ of the bottom ring were removed, and/or if mounted on a fiberglass mast, insulated from a metal mast at the bracket, or simply stood up on a flat roof without being attached to a metal mast, and with the coax wrapped into a cmc choke just below the connector?