AstroPlane up and Testing

[Starduster]

Will you be using an analyzer when you build your beam? I sure would be interested to know what kind of numbers you are seeing at resonance and at the ends of your <1.5:1 and your <2:1 bandwidths.

You will figure it out when you get your APB up and working I'm sure, so keep us posted on your progress.[/QUOTE]

I will be using an analyzer (MFJ) and will keep all informed. All I know is that the 6' long 35ohm coax. It is in fact RG-83 and it came with the beam, it was suggested to use it and not omit it. The beam was great for rejection. Forward gain seems pretty good.
I will start with duplicating the element length and spacing as the original a smuch as possible.

I was wondering, how about a 1/2 or 5/8 wave astroplane? What would that look like?

 

[Marconi]

I will be using an analyzer (MFJ) and will keep all informed. All I know is that the 6' long 35ohm coax. It is in fact RG-83 and it came with the beam, it was suggested to use it and not omit it. The beam was great for rejection. Forward gain seems pretty good.
I will start with duplicating the element length and spacing as the original a smuch as possible.

I was wondering, how about a 1/2 or 5/8 wave astroplane? What would that look like?

That's great that you will be using an analyzer. If you have notes maybe we can compare the AstroPlane by it self also.

Re: the RG83. If your jumper is RG83 then it is 35 ohms. My manual indicates that the jumper is dual RG59 which would be two 75 ohm lines in parallel doing about the same line impedance as RG83, like Jazzsinger suggested. I doubt if makes much difference until you try to find some RG83 maybe.

I think the AP is pretty sensitive to the relationships of the material tapers in its construction. If you maintain the relationships pretty close in your modifications that make it easily tunable, then I would bet you'll be fine.

Well SD'r, I use to claim the AP was a 5/8 wave, but now I believe it is an end fed 1/2 wave radiator with a 1/4 wave feeder. In my minds eye I see cancellation in areas at the bottom of the antenna and as a result could not see the feeder as a radiating part of the antenna that would make it a 5/8 wavelength, so I think it is a very effectively fed 1/2 wave instead. However, I'm open for debate, so I could be wrong.

 

[bob85]

i have seen people say its a 5/8wave so somebody agrees with you eddie, freecell said its 3/4wave while some say its just a 1/4wave groundplane,

the old citizen band magazine article would answer what the astroplane is if we could find it,

i think the lower portion is a tapered transmissionline, the spacing of radials to mast set impedance and radiation angle, according to the patent parallel radials produce radiation angles below the horizon,
mast length also effects radiation angle significantly, which makes me wonder if the optimun length mast for low angle radiation been 1/2wave or 9ft below the hoop @27mhz is to minimise antenna mode currents in the mast,

mine will be isolated and choked about 9ft below the hoop for my own curiosity:blink:

 

[Starduster]

What do you think would happen if you were to take a Stock Starduster which is basically a 1/4 wave groundplane and double the length of all elements. Would you now have a 1/2 wave Starduster?

It don't take much to be more in the know about antenna than myself so please tolerate weird questions.
At times I struggle with understanding that analyzer. The way I see it a person should shoot for;
x= 0 as close as you can get
R= 50 as close as you can get
SWR as close to 1 as you can get
All at your favorite frequency
Is that thinking correct?

My Astroplane At 26.757 reads:
R = 52
X= 4
SWR = 1.0
Impedance = 55
At 26.991 it reads:
X = 2
R = 46
SWR = 1.0
Impedance = 50
I think somewhere in between or near those frequencies is resonance
I can shift these numbers around by adjusting the length of the elements but really don't quite know what to shot for.
The SWR readings on the meter and the SWR reading on the LCD display are very slightly differing. So I suspect that the Impedance meter is somewhat subjective also.

I also took a look at the matching coax that came with the Astrobeam. Printed on the side is RG 83U so it is 35 Ohm and is 6' long.

 

[Starduster]

i have seen people say its a 5/8wave so somebody agrees with you eddie, freecell said its 3/4wave while some say its just a 1/4wave groundplane,

the old citizen band magazine article would answer what the astroplane is if we could find it,

i think the lower portion is a tapered transmissionline, the spacing of radials to mast set impedance and radiation angle, according to the patent parallel radials produce radiation angles below the horizon,
mast length also effects radiation angle significantly, which makes me wonder if the optimun length mast for low angle radiation been 1/2wave or 9ft below the hoop @27mhz is to minimise antenna mode currents in the mast,

mine will be isolated and choked about 9ft below the hoop for my own curiosity:blink:

The instructions mention at least 3 feet of mast below the round loop at the bottom of the antenna before any other suport stucture when considering a mast pole. You said yours will be choked at 9' below. Do you mean a choke in the feed line/coax?

 

[bob85]

sdr,
the patent is much more revealing than the instruction booklet, it explains that when the mast is less than 1/4wave in length below the hoop radiation angle rises, it also tells you what happens to impedance and radiation angle when radial flare is changed, me and eddie ( marconi ) have talked about this in the past,

yes i mean i want to isolate the 1-1/2" mast from its support structure about 9 feet below the hoop making the mast 1/2wave and wind a 5 turn on 4.5" form choke in the feedline in the same place,
i don't know if that will improve performance, it will so says the patent lower radiation angle over a mast that extends less than 1/4wave below the hoop,

my idea that it may be a means to minimise mast antenna mode currents is just an idea.

 

[loosecannon]

bob, i always wanted to try that with mine, but i dont want to cut my push up pole. they are getting hard to acquire.

i sure hope you end up trying it.

now im off to find that CB radio magazine article!
any guesses as to the year?
LC

 

[bob85]

this one, good luck,

http://www.worldwidedx.com/cb-antennas/51610-shot-dark.html

 

[Mr Clean]

I have heard that astroplanes pick up horizonal signals better than most groundplanes and wondered if anyone has found this to be true. I have a Astrobeam in the box that has been opened and the insulators for the outer elements are all thats missing. Would part with it if someone is intrested. Pigtail is there also.

 

[Marconi]

i have seen people say its a 5/8wave so somebody agrees with you eddie, freecell said its 3/4wave while some say its just a 1/4wave groundplane,

Bob, like I said in a previous post, right now I think the AP is an end fed 1/2 wave radiator. IMO, the first 1/4 wave radial element under the feed point is working against the mast as a non radiating feeder device, and transitions via the hoop to feed the end of the 1/2 wave radiating element that is opposite the feed point side of the hub. I’m also inclined to believe the AP is a 1/2 wave, because the antenna is used as a driven element for the AP beam. Another factor in my thinking is---we don’t typically see CB beams using 5/8 or 3/4 wavelength radiators as driven elements. In such cases we do see 1/2 and full wavelength elements used almost exclusively and this probably has a lot to do with the physical symmetry of the 1/2 wave radiating element. I’ve change my mind before on this issue, so I’m open for new ideas.

the old citizen band magazine article would answer what the astroplane is if we could find it,

I may have a source for this article, maybe the whole book.

i think the lower portion is a tapered transmissionline, the spacing of radials to mast set impedance and radiation angle, according to the patent parallel radials produce radiation angles below the horizon,

mast length also effects radiation angle significantly, which makes me wonder if the optimun length mast for low angle radiation been 1/2wave or 9ft below the hoop @27mhz is to minimise antenna mode currents in the mast, mine will be isolated and choked about 9ft below the hoop for my own curiosity

Bob, I don’t understand this last issue well enough to really talk about it. Maybe we can talk soon.

 

[packrat]

Starduster,

Can you show me some pics of your machine shop. I would like to see where you are making the antennas.
That would be cool.

 

[Marconi]

I have heard that astroplanes pick up horizonal signals better than most ground planes and wondered if anyone has found this to be true. I have a Astrobeam in the box that has been opened and the insulators for the outer elements are all thats missing. Would part with it if someone is intrested. Pigtail is there also.

Mr. Clean I have commented that I have seen such responses before, but it was with local horizontal signals only. I have never been able to detect the same difference with DX signals however. The response I saw was dramatic like you might see switching polarity on a beam sometimes. If that was not the case, then I would not make such comments. Since it doesn't happen with DX signals, it makes me unsure of what the cause was.

If you have a AP plus another vertical setup with a switch box, and you have a bud with a horizontal beam, you might try to duplicate what I did. Needing several antennas up and working complicates being able to see these affects. Not many operators will have the antenna setups necessary to test, so don't get all excited about it. If this happened when DX was working, I would really be sounding off about it.

If you think you might have such a setup and a buddy to test with, then let me know and I will give you the details of exactly what I did.

 

[Starduster]

Mr. Clean I have commented that I have see such responses before, but it was with local horizontal signals only. I have never been able to detect the same difference with DX signals however. The response I saw was dramatic like you might see switching polarity on a beam sometimes. If that was not the case, then I would not make such comments. Since it doesn't happen with DX signals, it makes me unsure of what the cause was.

If you have a AP plus another vertical setup with a switch box, and you have a bud with a horizontal beam, you might try to duplicate what I did. Needing several antennas up and working complicates being able to see these affects. Not many operators will have the antenna setups necessary to test, so don't get all excited about it. If this happened when DX was working, I would really be sounding off about it.

If you think you might have such a setup and a buddy to test with, then let me know and I will give you the details of exactly what I did.

This would all make sense as skip tends to scramble polarity.
Also you had mentioned that you took the top hat off of your AP and put a straight radial on top. The patent states that the upper radial should equal the length of the lower flaired radial. I wonder why you were around the 70 to 80 inch length when the lowers are 96. Unless I am missing something.
Please forget about all of the other stupid questions that I had asked.

 

[Starduster]

Starduster,

Can you show me some pics of your machine shop. I would like to see where you are making the antennas.
That would be cool.

I don,t really like to post these kinds of photos but a couple shoudn't hurt. You never know.
Not much just some old clunker machines.
They can make the parts though Photo 2

 

[Marconi]

What do you think would happen if you were to take a Stock Starduster which is basically a 1/4 wave groundplane and double the length of all elements. Would you now have a 1/2 wave Starduster?

You would have a big matching problem and the ground radials would probably dominate the vertical portion of the antenna pattern.

It don't take much to be more in the know about antenna than myself so please tolerate weird questions.

At times I struggle with understanding that analyzer. The way I see it a person should shoot for;
x= 0 as close as you can get
R= 50 as close as you can get
SWR as close to 1 as you can get
All at your favorite frequency
Is that thinking correct?

There can be issues with feed lines sometimes that affect the meters results, but the factors above are good goals. It is always best to take these readings for tuning purposes at the feed point and at the working height---albeit inconvenient.

My Astroplane At 26.757 reads:

R = 52
X= 4
SWR = 1.0
Impedance = 55
At 26.991 it reads:
X = 2
R = 46
SWR = 1.0
Impedance = 50
I think somewhere in between or near those frequencies is resonance
I can shift these numbers around by adjusting the length of the elements but really don't quite know what to shot for.

This is a bit low in frequency. When you made the mod to the antenna to make it tunable, did you change any of the original dimensions or are they the same and you just added the larger tubing?

I think we talked about this the other day and you said when you tuned the antenna low to the Earth it was good at 27.205, but when you raised it up higher the resonance or the good readings showed the antenna drop down in frequency. That could have been another thread I was on where this topic came up.

The SWR readings on the meter and the SWR reading on the LCD display are very slightly differing. So I suspect that the Impedance meter is somewhat subjective also.

I also took a look at the matching coax that came with the Astrobeam. Printed on the side is RG 83U so it is 35 Ohm and is 6' long.

How many digits read out on the LCD display for SWR? My meter reads two places past the decimal. Yours could read only one digit past the decimal and that compared to the analog meter may differ.