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The AstroPlane Another Viewpoint

Marconi

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Oct 23, 2005
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Below is a report on the Avanti AstroPlane antenna done back in the days. I posted some numbers, and some Internet exhibits that claims Avanti professionally tested their AstroPlane (A/P). I did this just for a little history on the AstroPlane.

I have documents and posted below 2 Eznec models that tend to support Avanti claims...who did the tests, and how it was done. I also provide some verification information on the author of the test report.

i studied the details of this report and tried to follow the ideas for their construction, so that I could try and duplicate their results.

So, this is what I hope these models will show us.


I scaled an old Asto Plane model to 144 Mhz. I started with a model that had a full 1/4 wave radiator. I did this for my convenience in modeling.

IMO these 2 models tend to support much of what Avanti has claimed in their advertising.

In the PDF files below is the Avanti's AstroPlane test report, an old ad I found in CB Magazine. I found the Technology News report talking about the Engineer Avanti used to do this research. Followed by the 2 models in the PDF file posted below.

Sorry for the poor copies, working with old copies of copies is tough. If you can't see something clearly...try using the PDF print. The Zoom functions might help improve the images.

Models: AstroPlane at 144 MHz set 72" inches to the feed point (1 wavelength high - see the report).

1. shows the antenna model in Free Space (FS). This means all the ground and wire resistance effects for the model have been removed. This is basically done so we can test the accuracy of the model. See the 1st page of each model, the Eznec Control Panel. At the bottom it shows the Average Gain results (AG). AG results show 1.662 = 2.21 db. In this case the 2.21 db value after the = is a correction value for the gain and is due to an overstated or understated in gain, reported as an error for the model.

If the value -2.21 db was noted with a (-) then the gain is understated. Then we would add this value to the gain reported by the model. Then, this is consider as the accurate gain for the model.

If the value 2.21 db, as stated for this model with a (+) that is blank, the gain is overstated and we would subtract the value from the gain reported by the model. Then can consider this is the accurate gain for the model.

2. shows the antenna over the Eznec feature for Real Earth. This simply means the opposite of FS, where the losses were removed.

Depending on the sign (+ -), just add or subtract 2.21 db to the gain reported for these 2 models and we will see the accurate gain that the model should report.

IMO, none of this means the A/P is bad, weak, a dummy load, or is deficient. It is a great antenna and better in other ways that only a few will likely acknowledge.

Make your own conclusions about the likely gain for the AstroPlane as reported by Avanti advertising and by others making knockoffs of the great vertical 1/2 wave antenna design.
 

Attachments

  • The AstroPlane - Another Viewpoint.pdf
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  • AstroPlane models at 144 MHz in test report.pdf
    2.5 MB · Views: 30
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Homer, thanks for the patent.

My intention in this thread was to hopefully demonstrate using an A/P model, that was in error, and that error resulted in the gain being overstated. These two models at 144 MHz show gain >4.00 dbi to be overstated similar to what Avanti published in their ads @ 4.46 dbi.

Homer, I was working on the history of the A/P and I found an old model that showed the gain overstated @ >4.00 dbi.

I said to myself "WA-LA" maybe this is how Avanti got the big gain they reported for this vertical 1/2 wave antenna.

I know a 1/2 vertical mono-pole will not produce 4.46 dbi gain. It is closer to 2.14 dbi. It is also my opinion that steering the TO angle of the A/P, if possible other than changes in elevation, those results would be minimal at best, and will only happen in a Free Space model.

Based on my models, I have never seen an A/P over Real Earth suggesting steering. Avanti is showing us FS models and they tell us "...measurements are given in Figure 1, along with the calculated performance of a 1/2 wave antenna in free space, for comparison"

Check out the last sentence above Fig 1, in the report I posted in my post #1
.
 
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So does this new AstroPlane perform like the old one?

One of my first antennas I used back in the 80s was an old AstroPlane that I got from a family member. That antenna had really good ears and the over all ground noise was really low. I remember being able to pull out stations 60-70 miles away late at night when conditions where calm. It was mounted 25 feet in the air.
 
So does this new AstroPlane perform like the old one?

997, welcome to the forum.

I've had both and I noticed very little difference even when compared TX/RX side by side or with the antennas standing alone.

I think all of these antennas are difficult to find anymore.

I also find the Sirio New Top One has a bit wider <2.00:1 SWR bandwidth and within reason the antenna is tune-able.

IMO these antenna were great.
 
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No model over real earth will suggest steering, ever. You have to use free space to see it.

DB I agree, I don't see steering of the TOA for my A/P model over real Earth. Currently I don't see steering with my Free Space models either.

So, does your comment suggest we can seen steering while using an A/P model set in Free Space?

If so, I sure hope you can find time to use the A/P 4NEC2 code by GHZ24 that I linked for you the other day, and maybe show us a FS model that shows steering or a TOA at or below the horizon or exhibits a tendency to do so.

Here is what GHZ24 said about all of the models he posted back then.

Starting out building models can be overwhelming ,but running an existing model is relatively easy
Just copy the "code" for the model paste into a text file and rename or save as XXXXX.nec move it to the models folder of 4nec2 and open it with 4nec2 (the little folder icon on the left).
 
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So, does your comment suggest we can seen steering while using an A/P model set in Free Space?

Yes, but as I recall it took quite a big change for a rather small amount of steering. I modified the model as per the patent, and only saw a difference of 4 or 5 degrees.

If so, I sure hope you can find time to use the A/P 4NEC2 code by GHZ24 that I linked for you the other day, and maybe show us a FS model that shows steering or a TOA at or below the horizon or exhibits a tendency to do so.

I have been working long hours for a while, and will be for the foreseeable future. If you want to see this done, you are going to have to do it yourself. Besides, if I were to play with an Astroplane model I would make my own. Nothing against ghz24, his models are great starter models, but I prefer my own work. So please stop asking me to use someone else's models. Without good reason, its simply not going to happen.


The DB
 
That's okay DB, but you tell us all of your 4NEC2 models were lost in a computer failure. So, I was thinking his code might be helpful in getting a bases to start and then you could modify the model as you wished.

Nothing sinister going on DB, I was just trying to share.
 

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