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Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 177
Registered: 9-2004
| | Posted on Thursday, January 27, 2005 - 5:22 pm: | 
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i think i have found the new QTH. so i will be moving in the next two weeks. in this location i will be able to run the mast for my top one all the way to the ground. in the instructions provided with the antenna it states that you should make sure to get a good metal to metal contact at the top mast to antenna clamp.
my question is: will a longer mast, (about 32ft.) connected to a ground rod at the bottom atffect the performance of the antenna. in a normal groundplane antenna i already know the answer to this question, but i have never used this type of antenna before. so does anyone out there have their top one mounted in a similar fashion?
thanks in advance for any help.
matt |
Tech833
Moderator
Username: Tech833
Post Number: 970
Registered: 8-2002
| | Posted on Friday, January 28, 2005 - 12:23 am: |
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It will still work fine. No difference. The mast can be as long as you wish, as long as it is all metallic and bonded (electrically connected with no insulators in it). |
Marconi
Intermediate Member
Username: Marconi
Post Number: 332
Registered: 11-2001
| | Posted on Friday, January 28, 2005 - 3:11 am: |
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Hey KV, I have one of the Top Ones from Coppers and I do not see the info you talk about in the doc's. On the back of my drawing for the parts of the antenna there is some almost unintelligible text about the antenna, but no where does it state as you note "...that you should make sure to get a good metal to metal contact at the top mast to antenna clamp."
My doc's read, "To mount it carefully follow the enclosed drawing; tighten screws so that you mast not do it again after some time then secure it on top of the stub." I take this to mean that you should secure the antenna with the top of the mast at the top of the stub only (not above) and tighten it down so that it does not slip or move over time in the wind and weather. I don't see it having anything to do with the grounding idea that you imply.
Personally, I don't believe this antenna needs to be grounded or connected to a metal mast in order for it to work or to work right. It is a good idea in case of lightning, but it is not necessary. I have mine attached to a 10' mast clamped on top of the back of my garage and it is not grounded to anything. It doesn't even touch the ground. As best I can tell it works just fine. |
Marconi
Intermediate Member
Username: Marconi
Post Number: 337
Registered: 11-2001
| | Posted on Sunday, January 30, 2005 - 2:35 am: |
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833, you know my position on this issue from my post above. In answer to KV's question you state,
"It will still work fine. No difference. The mast can be as long as you wish, as long as it is all metallic and bonded (electrically connected with no insulators in it)."
Is it your contention that in order for the antenna to work or work right, that the mast has to be all metal and bonded as you note, or is it a safety thing you are suggesting here?
KV, maybe you can tell us what it is that you know to be true of the affects of grounding (as you note) on performance of a normal ground plane antenna.
Also if you are suggesting to us that the Top One is a ground plane antenna, maybe you can describe to us which part is the radiating element and which part is the ground plane? Get your OHM's meter out and check this one out.
Just trying to keep you guys straight and on point here. If I'm wrong about anything then I will tell you I'm wrong and I will have learned something in the boot. |
Tech833
Moderator
Username: Tech833
Post Number: 982
Registered: 8-2002
| | Posted on Sunday, January 30, 2005 - 11:13 am: |
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Marconi,
You said, "Just trying to keep you guys straight and on point here. If I'm wrong about anything then I will tell you I'm wrong and I will have learned something in the boot."
O.K.,
"Is it your contention that in order for the antenna to work or work right, that the mast has to be all metal and bonded as you note, or is it a safety thing you are suggesting here? "
There needs to be some metal between the two vertical elements to keep the impedance correct. My comment ablut a bonded pipe was for grounding protection. Safety as you put it.
"Also if you are suggesting to us that the Top One is a ground plane antenna, maybe you can describe to us which part is the radiating element and which part is the ground plane? Get your OHM's meter out and check this one out. "
Glad to. The Top One IS a 'ground plane' antenna turned upside down (current node above voltage node). The radiating element is the vertical extending down from the coax connector and its return path is the vertical going back up to the mounting bracket. The 'ground plane' is the vertical above the mounting bracket and the radials (top hat) above that.
Ground effects on a 'normal ground plane' are well documented, and I believe you are aware.
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Marconi
Intermediate Member
Username: Marconi
Post Number: 343
Registered: 11-2001
| | Posted on Monday, January 31, 2005 - 1:10 pm: |
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833 you and the Kid are correct. After reading the patent report on the Astro Plane antenna and hearing what you both had to say about the Astro Plane Ground Plane antenna, I am convinced that it is an upside down Ground Plane antenna.
Some years ago I had some disassembled parts from an Old AP around and I was checking it out with and OHM's meter trying to figure it out a bit. I had the hub, the first section down out of the feed point, the bottom ring with the first two 1/2 sections attached and going up, and the top element with the top hat attached. I installed the top section and I showed an open down to the lower part and a short to the hub. It looked wrong, thinking it was the top of the antenna. I started asking guys that had them if they knew what I should see when doing such a test. Some said they didn't know or that their antenna was in the air and could not be tested. Of all the ones that could check this out, every one said that the top part with the top hat showed to be electrically insulated from the hub and to be connected to the bottom section and to the center conductor at the feed point. So I said to my self, maybe this is how they get the length to act as a 5/8 wave. I also wondered if it was really a 5/8 wave how they were able to direct feed this non-resonant element without some matching.
Well a while back a got a complete antenna and installed it and it works just fine. I get a little RF on the feed line, but otherwise it works pretty good.
I never gave the OHM's test any thought before seeing this thread and reading the post from Kid Vicious about his antenna. All those old questions came back so I said you both were wrong based on that old info.
I plan to OHM test mine in a few days and if I find something different then I will let you know, but I believe you are right. I expect to find the ground plane just as I did some years ago and not as all those guys told me.
Maybe you can explain how they get that it is a 5/8 wave?
I never fail to learn something even with my foot in my mouth.
Thanks
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Pintail617
New member
Username: Pintail617
Post Number: 8
Registered: 2-2004
| | Posted on Monday, January 31, 2005 - 1:19 pm: |
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How do you adjust these antennas or they pretuned? Just wondering, I am considering buying one. Thanks. |
Pintail617
New member
Username: Pintail617
Post Number: 9
Registered: 2-2004
| | Posted on Tuesday, February 01, 2005 - 9:27 am: |
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KD,
Thanks for the information. I think I may have to give this one a try. |
Tech833
Moderator
Username: Tech833
Post Number: 985
Registered: 8-2002
| | Posted on Tuesday, February 01, 2005 - 10:05 am: |
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I can explain how they get 5/8 wave from the design. The marketing department.
To the marketing department- It is an upside down folded 1/4 wave ground plane. But, if you take out your tape measure and your imagination.... The return path back to the hub would make the feedpoint-to-shunt measurement a 1/2 wave. Add the ground plane support and you have a 5/8 wave. Maybe? |
Marconi
Intermediate Member
Username: Marconi
Post Number: 344
Registered: 11-2001
| | Posted on Tuesday, February 01, 2005 - 11:56 am: |
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I agree 833. Looks like sort-of-a' upside down starduster to me. I doubt the AP would allow for a natural match using direct fed if it really was a 1/2 wave or a 5/8 wave. Looks like a 1/4 wave radiator to me.
BTW, I don't have any problem with a 1/4 wave antennas. From my own experience I have found that I have never really lost a contact, using a antenna with a 1/4 wave radiator (SD'r), that my local buds were able to make with their big gun antennas. I might not make quite as big a signal at the other end, but seems they always heard me a little bit. I also recall once getting my SD'rs hub up to about 65' one time. The hub was almost to the tip of my old Sigma IV and the TX/RX signals were very often about the same at both ends. You really have to try it to see it. That too is not the true test of any antenna, but doing one this year and another two years ago sure don't cut it.
Seems simplictity is just not in vogue anymore? |
Tech833
Moderator
Username: Tech833
Post Number: 988
Registered: 8-2002
| | Posted on Tuesday, February 01, 2005 - 4:59 pm: |
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The main difference between the Top One and a Starduster is the return path for the radiator. Picture this antenna here, but upside down- http://www.andrew.com/products/antennas/bsa/DB201-A.aspx |
Marconi
Intermediate Member
Username: Marconi
Post Number: 367
Registered: 11-2001
| | Posted on Wednesday, February 16, 2005 - 2:48 pm: |
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833 and Kid Vicious, I have to give it to you guys again, you were right and I was wrong about this old AP idea. I have been at it again, trying to understand how it works.
Kid you were right and I really need to apologize for questioning your veracity in your claim that the support mast needed to be very secure for both safety and operations. It is vital to operations as well as safety.
833 you too bud. The mast needs to be metal and secure to the hub, because the relationship it has to both the vertical 1/4 wave elements spread a bit to the sides of this mast determines the impedance at the feed point. It is all right there in the patent document and I missed it.
I was confused by the fact that I saw a short at the feed point, and questioned that, using a 5/8's end fed element if that is what it is. However, the short is right there, but only when the opposite side of the hub makes complete circuit connection via the two elements and the bottom horizontal loop, making what looks like a radiating loop to me. Disconnect that and the feed point shows open. There is the missing insulator that I did not see.
I figure that since the feed point is located at the A plane, as it is referred to, that this point must be a current null. This is as you noted 833, because the current has to flow around this loop in order to get back to the feed point from the other side of the hub, and point A is a 1/4 back from the voltage node at the bottom loop end of the first 1/4 wave element, in what I will call a larger overall loop. Don't know what size it is, maybe a bit larger than a 1/2 wave, mabye a 5/8 wave. I think that is what you were talking about 833 when you said the return path for the antenna.
Haven't got it all yet, but I think I'm at least plowing another path. Been there before.
Is this thing some kind of modified loop of some sort, maybe like a folded dipole?
How does the shortened 1/4 radiator at the top come into play here? We know for sure that if it is not there, then the thing will not match out according to what happened to 1861, in his thread in another area of this forum about a new Top One. It sill doesn't look like a ground plane to me.
Thanks again.
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Marconi
Intermediate Member
Username: Marconi
Post Number: 372
Registered: 11-2001
| | Posted on Wednesday, February 16, 2005 - 7:19 pm: |
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More is coming soon on the Astro Plane. Look in the Product Review section. |
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