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Astroplane, what is it? 1/4, 1/2, 5/8 ??


Mark Scannura said:
Found this interesting read on the Astroplane done a few years back. So, really what was the Avanti AS? What about the the Siro TO. Is it the same principle of how the Avanti used the 9 ft mast below the basket as part of the antenna?
http://www.cb27.com/tecnica/astroplane
Click to expand...

We have done far more in the way of discussing this antenna than that site talks about. Further, some of what is on that site is suspect at best, for instance, that model, whos description said it is over real earth, which would be fine, however, the model shown is clearly over perfect ground. To be fair, I'm reasonably certain that he didn't actually do the modeling himself.

Not trying to pick apart all of his article, but the part where he shows that the antenna appears to be a 5/8 wavelength antenna, I will also point out that that is mentioned in the patent, however, if you model the antenna and examine what is happening with the currents, that diagram and the current distribution of the antenna do not match, and it is the currents that determine the electrical length of the antenna.

If you want a more thorough annalysis on this antenna you can try this thread.

https://www.worldwidedx.com/threads/astroplane-best-vertical-antenna-ever.160317/

Staybolt said:
Here we go............ a debate until the cows come home.
Click to expand...

You know, you have your interests when it comes to radio, and we have ours. Are we hurting anyone with our discussions? And what is wrong with debate? You know you don't have to read the threads with said debate, and you can even put those of us who have such debates on ignore. You have the tools at your disposal to hide most if not all of what you are complaining about.


The DB

Edit: Removed a line that might be taken the wrong way.
 
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Yes i do have my interests and the AP has been hashed and rehashed so many times on the online forums over the years its ad nauseum.
 
I think what I've been reading on the AP and later clones is they are not all built the same. Avanti claimed the AP was a 5/8 wave. I see Sirio calls their version a 1/4. Not sure about Tegra. Was the Avanti claim false?
 
The Sirio is not the same design
as the A/P. Sirio top one has a gamma match. The Ap you have to look at carefully to see. I still don't understand how it works lol. I do however have both of these antennas :)
 
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Mark Scannura said:
I think what I've been reading on the AP and later clones is they are not all built the same. Avanti claimed the AP was a 5/8 wave. I see Sirio calls their version a 1/4. Not sure about Tegra. Was the Avanti claim false?
Click to expand...

I don't think so. Just my opinion.

I think probably when the A/P was introduced by Avanti the roar in CB back then was so obviously a big deal that many today might not have a clue what CB was back then vs. today.

I also remember that was about the time when the high gain antennas were being introduced as well. So, IMO Avanti probably felt they needed to get into the "craze for the times" and say their A/P was a 5/8 wave... just to try and keep up with Radio Shack and a few others...saying their versions of the 5/8 wave, like the HyGain CLR2, was a collinear antenna.

IMO, that was all CBBS. The AstroPlane is a center fed 1/2 wave radiator that has a design that tunes the antenna to match the 50 ohm coaxial feed line at resonance very closely.

Some will argue, and maybe correctly, it is a 1/4 wave ground plane that just looks different and also is able to tune the antenna to a good match for the typical CB radio.
 
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Mark Scannura said:
Does anyone know if gamma fed in this antenna application is better than the original AP version?
Click to expand...

In my comparison testing of these two on-air, there is little to no difference that I could tell.

Below are two Antenna Work Sheets that I did back in 2011 that compares the bandwidth curves for both, if the are still readable. You might try zooming in on the images a bit. Check the top line of the PDF file and increase the zoom,

or hover over the top of the top of the page for the PDF file and "click the mouse" a menu of options will popup. Select the + several times to zoom in.

IMO. the antenna with a gamma is noted to be more broad banded. I also believe an antenna that can use a gamma is usually a bit inductive, so the gamma will allow for a bit more bandwidth and these reports show that as one difference.
 

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Mark Scannura said:
Does anyone know if gamma fed in this antenna application is better than the original AP version?
Click to expand...
Whichever version you get, I would be SURE to assemble it exactly to the specified lengths. SIrio uses the metric system to gauge all dimensions in their assembly instructions, so I went out and bought a tape measure that was in mm/cm. Made adjusting the gamma a snap and only cost a couple of bucks more - knowing that I had the rest of the antenna nailed down to length/dimension specifications. I bought/built the Sirio V4k.

If it was me making this choice; think I would get the gamma model and build it right to specs. . .
 
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Marconi said:
In my comparison testing of these two on-air, there is little to no difference that I could tell.

Below are two Antenna Work Sheets that I did back in 2011 that compares the bandwidth curves for both, if the are still readable. You might try zooming in on the images a bit. Check the top line of the PDF file and increase the zoom,

or hover over the top of the top of the page for the PDF file and "click the mouse" a menu of options will popup. Select the + several times to zoom in.

IMO. the antenna with a gamma is noted to be more broad banded. I also believe an antenna that can use a gamma is usually a bit inductive, so the gamma will allow for a bit more bandwidth and these reports show that as one difference.
Click to expand...

Thanks for both replies Marconi.
 
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