ASTROPLANE best vertical antenna ever?

[Marconi]

Bob, my A/P model is not showing a good match, like I think it should. And I would not know from experience, because I've never owned a real A/P. I do have some parts I took down around the neighborhood however, but they were all badly damaged, and not one was anywhere near complete.

The Old Top One (OTO) shows an almost perfect match with its dimensions, from my checking, and from Lossecannon's recent checking...that supported my measurements.

So, I figure the matching problem is possibly due to some errors in the dimensions I used on the A/P...so it is showing me a worse match.

This is not another request to get some accurate exposed length measurements however, just an update on how I plan to try and finish your Do's and Don'ts list, that you posted above.

With the A/P model, I can go from using 197" mast to 220" mast and the SWR goes from 1.4xxx to 1.6xxx. That probably wouldn't bother you and Steve technically or functionally, but a lot of CB folks would probably not understand...and put any ideas for the A/P in the garbage heap. I don't think that is necessary, but here we are.............

The OTO, model changes match very little with such a change in mast length...as noted above. That did surprise me though. You'll see, these models will show very little change in the match when I post it.

They will be in Free Space, so I can keep track on the accuracy...and I will do nothing to the models to fix any thing except to make the full 1/4 wave radiator resonant. As a follow up, I might try a real Earth model when I compare the short radiator with a Top Hat to the full 1/4 wave model.

That said, I'll use my OTO to compare the models with a Top Hat vs. the full 1/4 wave radiator with a 220" of mast. I'm going to try and go slow...trying not to make some sill mistake like I did the other day, with the 3/4 wavelength mast.

Bear with me.

 

[bob85]

Eddie,
The old cte top that was sold here years ago and the astroplane are tuned for the middle of your band so i don't know why you are having trouble with the match of just the astroplane,

The only tuning you can do on the astroplane is pull the legs in and out on the spreader, everything else is fixed length.

 

[Marconi]

Eddie,
The old cte top that was sold here years ago and the astroplane are tuned for the middle of your band so i don't know why you are having trouble with the match of just the astroplane,

The only tuning you can do on the astroplane is pull the legs in and out on the spreader, everything else is fixed length.

I agree Bob, that is the way I would think the model should work too. I don't know why the model does not respond with a good match like the OTO model does. The OTO tuned almost perfect in CB, just as it came out of the box. I can't explain why the A/P model does not respond like the OTO...it should.

This is why I asked you to help me out and give me the exposed lengths for your antenna, just in case I guessed wrong on some of the dimensions you sent me in 2014. So, I'll be using the OTO to compare the Top Hat versions vs. the full 1/4 wave version.

Here is the model I titled as "AP Bob 197"Mw6"M2R bracket FS." Here the model is too the dimensions as noted on the antenna view. I do not see how these dimensions can show such a bad match as noted.

I have always had to adjust the dimensions of Avanti models I have made in order to see a reasonable match. I think you still lack confidence in modeling...unless you see something in a model that you can agree with.

Is what you suggest above in your previous post #437, quoted at the top of this post, what you did to get your A/P to show a good match?

I include such a model in the PDF files below. My models before I got your dimensions were always mostly a guess too. So I was hoping, I just made some bad guesses, and if and when I got the right #'s...maybe everything would out just fine.

I'm still waiting, and I don't care that I can't seem to get the model to work better...I have no doubt the real antenna works fine, even if I can't prove shit with a model that does not respond as it should. Maybe you should get hold of Henry or DB and see if they can make you an A/P model that works with no adjustments to the specs.

The models below are to show what I see on this end.

The meaning of the Title descriptions:

The w6"M2R bracket is the distance form the radials to the mast at the mast to radial bracket. 6" inches on each side in this case. You can probably figure out the rest of the title.

To fix the resistance on the A/P i had to set this space at 4.5" on each side of the mast and I included that too...in case the results is all the matters to you. I'm not claiming this is right...it is what it takes to make the resistance closer to 50 ohms. I did nothing to fix the reactance...but I can do that too if that change in dimensions will make you happy.

NOTES: At the bottom of the page #3 of the PDF file below, is a note to wire #43, and that is the 197" mast inside the antenna and extending close to a 1/4 wave below the loop. It shows 196" for a 1.50" diameter mast, but I fixed the problem that DB told us about when he talked about his 4Nec2 allowing him to only use a 1" mast inside the antenna. So, in this case we have 196" + 1" = 197" inches for the mast.

Nothing special about this length, it is just the length i found a long time ago that seemed to work best for me. Later on I used DB # 220" inches and it does improve the gain a bit more.

If you wonder why I did this 1" thing to the top of the mast at the FP hub, I can explain this as the only way I can use a 1.50" mast in this case. Eznec give me a critical error message just like DB told us. So, if I wanted to use a 1.50" mast from the hub to the ground then this trick to fool Eznec a little and 1" will do it.

I also attribute to Bob the fact that 1.50" inches in diameter for the mast for the A/P...is the best diameter in this case.

See Bob dimensions mater in modeling, just like they do with real antennas. So, I'm hopeful that the problem is a dimension problem...so I can get the A/P model to working like I think it should.

1. is your dimensions from 2014.

2. is my new model with specs I took from your information in #1 above. i added notes giving the dimensions for all the wires I used. Note the SWR bandwidth curve, and the Average Gain results...making the model undependable for accuracy. Note the match I talked about and the resonance at the low end of the CB band.

3. is the same model at #2, except I took you advice and changed to space between the raidals at the radial to mast bracket. Note the AG results...it is worse, but the resonant frequency got a little better, but still low in the band.

The model is not a good model. Could it be the dimensions?

 

[Alexis Mercado]

I finally found a dinosaur an NOS original Astro Plane Antenna. I just installed it today. Here are some picks. It is around 36 feet off the ground. Original box instruction pamphlet included.

SWR as expected. It is curious they classify this antenna as a 5/8 wave antenna. ( see pics )

 

[bob85]

Eddie,
I set the astroplane to the spacing in the instructions & had low vswr with the 1.5" mast,

its possible but unlikely given the choke & ferrite I have on my coax that common mode on the coax was effecting where my low vswr was,

I doubt that for few reasons, a lack of noise from electrical goods & no change in vswr when I add a patch lead or move the coax around or pick coax up off the ground.


I do see something to look into that I remember reading about NEC,

all segment lengths in transmission-lines should be equal and junctions should be parallel,

if you look at the oto model vs astro model the junctions in the mast are not level with the junctions in the radials on the astroplane up around the feed-point,

I believe that would cause an issue with NEC but no idea how much of an issue.

 

[Marconi]

Alexis, I understand if you can't answer my questions about your dimensons. At least I have the questions on record...if you ever take it down to check it out...maybe if you have time and can remember, maybe you could provide me with a few exposed metal dimensions?

In the image below can you tell me what the space between the center of the radials is at the mast to radial bracket...the point along the FG rod where the top and bottom radials connect with the clip.By the way, the clip in the image below does not look to be touching the bottom radial at all, and I'm not sure if the rod and clips shouldn't be a bit lower. I took several old A/P down of the years. They were broken up and not being used. None of those I took down for folks had the bottom radials or the loop at the bottom. They looked to me to have come loose and just fell to the ground.

I wish I had talked to you before you got her up. But I am happy for you getting this prize. I think you are going to enjoy the A/P, and if you don't have any common mode currents problems on your feed line and mast...that bugger should operate real quite during very good low noise conditions.

Also, do you think you can move the radials closer or farther away from the mast, even a little bit? That is assuming the clips holding the rod secure are loosened a bit? The A/P Patent tell us this space can control the Resistance in the antenna. What I've seen so far is on a stock A/P and the length is typically close to 6" inches from center of radial to center radial...for the two radials in the bottom of the A/P.

Also in this image below, do you know how long the swagged part is at the clip on the radial...where the top and bottom tubes connect together? Sorry if I've asked you the same question already.

I think both top and bottom radials come 48" inches long, but parts of these 48" inches tubes are not exposed tubing. I use only the exposed lengths of tubing in my models or else the models can come out with errors.

By the way...shouldn't the clip on the radial be squarely in the middle of where the two elements

What dimension are you measuring in the image below.

It looks like radiator and the exposed part is 46" inches if the other end of the tape is at the very top at the level of the radials.

The mounting bracket looks to be about 2.25" tall.

Does the radiator go down into the bracket to the bottom?

Did you measure the exposed radials lengths or any other parts?

 

[bob85]

Alexis,
back when the astroplane was deveoped & marketed people were brainwashed into thinking a 5/8wave had some majic gain over shorter antennas,

so there was a reason to call your antenna 5/8wave & not 1/2wave, it sold antennas.

its a myth comparable to many people thinking a slim-jim has twice the gain of regular j-pole when they have about the same gain & performance.

 

[Marconi]

I do see something to look into that I remember reading about NEC,

all segment lengths in transmission-lines should be equal and junctions should be parallel,

if you look at the oto model vs astro model the junctions in the mast are not level with the junctions in the radials on the astroplane up around the feed-point,

I believe that would cause an issue with NEC but no idea how much of an issue.

Thanks Bob, I'll check that out.

Generally all of my models use a 3" segment length, when I can. So, if i can keep the 3" inches equal 3" or close, throughout the modeling process, this issue should be alright.

BTW, this issue has been discussed in the discussions with the S4/NV4K.

Do you know which model you saw...they all have unique titles. That would be helpful.

BTW, I found an old AstroPlane model I did in 2013, when I was making those models with the rectangle shape mounting and feed point bracket instead of the 2 short wires that DB got me to using. It also has a fuil length 1/4 wave radiator instead of the shortened radiator with a Top Hat.

Maybe I'll post that if it checks out. It is not According to Hoyle, but I think it works.

Bob, I just saw a post where Alexis got a A/P and put it up. It may be in this thread. He has pictures, and one shows the rod, clips, mast and a radial. I see the clip is not touching the bottom tube with the swaggend top end piece. Check that out and see if his antenna might be subject to fail due to the problem you have talked about over time...saying Avanti got that radial business upside down.

 

[bob85]

This one Eddie,

https://www.worldwidedx.com/attachm...el-that-does-not-show-a-good-match-pdf.40462/

look at the junctions, they are half a segment out of level, your oto models look more as they should be when modeling transmission-lines,

i have just been up in the loft to measure my astroplane,

from top of bracket where the elements end to the bottom of the clip that hold the hoop level my astro measures 94"
the hole for hoop is about 1/2" up from the tip,

the upper 1/4wave does sit fully in the bracket overlapping the lower element so its 48" minus the depth of the bracket you see in Alexis's image.

Alexis got the clips in the right place crushing the upper tube onto the lower tube, mine are a little closer to the end of the fiberglass rod.
it does look flimsy but mine held up ok,

i liked the old style expanded tubes better.

yes you can manipulate resistance by moving the legs in and out,
by doing that you are changing the characteristic impedance of the transmission-lines seen in parallel with antenna mode impedance.

 

[Marconi]

I do see something to look into that I remember reading about NEC,

all segment lengths in transmission-lines should be equal and junctions should be parallel,

if you look at the oto model vs astro model the junctions in the mast are not level with the junctions in the radials on the astroplane up around the feed-point,

I know your are right.

The 1' section of the mast I added at the top, skews the nice 3" segment alignment for the model, but without doing the 1' fix, I can't use a 1.50" mast for the mast.

I think I will try making the 2 short wires at the feed point a .25" or .50" longer or shorter and see if I can get the model to use the 1.50" mast without the skewing of the segments for the mast and radials.

 

[Marconi]

This one Eddie,

https://www.worldwidedx.com/attachm...el-that-does-not-show-a-good-match-pdf.40462/

look at the junctions, they are half a segment out of level, your oto models look more as they should be when modeling transmission-lines,

Thanks for the link Bob. Like I said all the recent models I tried to use the 1.50" mast, but Eznec is having none of that.

When I get the error message using the 1.50 mast all the way from hub bracket to ground, it says Wires 1 & 2 the short wires center of wire 1 end segment within wire 42.

Measure the radial tube spacing, center to center, for the top radials...right below the hub Bob. My Old Top has the radials at 5.75" inches apart Center to Center. Each side is 2.875" and not 3" inches.

My OTO does not have the error problem using a 1.50" mast from hub to ground, because this little difference was causing the problem with the A/P.

Loosecannon's spec sheet also shows the radial spacing at the hub is 2.875" inches.

 

[bob85]

The oto hub you sent me is still at the old place so i can't compare them at the moment but i will recheck the astroplane hub for you back in 5minutes.

right under the hub as close to the tube centers as I can get it with my eyes & measured with a steel engineers rule my astro measures 6-1/16"

 

[Marconi]

Loosecannon's spec sheet.

 

[Marconi]

Old Top One model shows wires 2 and 3 plus the mast wire #38 at 1.50" diameter.

You''ll have to use the Zoom feature.

 

[Marconi]

The oto hub you sent me is still at the old place so i can't compare them at the moment but i will recheck the astroplane hub for you back in 5minutes.

right under the hub as close to the tube centers as I can get it with my eyes & measured with a steel engineers rule my astro measures 6-1/16"

I'll try it Bob. Maybe that is why the extra 1/16" you said what you say below.

Alexis got the clips in the right place crushing the upper tube onto the lower tube, mine are a little closer to the end of the fiberglass rod.
it does look flimsy but mine held up ok,