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Message |
    
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 30
Registered: 12-2002
| | Posted on Wednesday, January 17, 2007 - 9:01 am: | 
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I was wondering if the performance of the astroplane would improve by removing the top radiator and replacing it with a 102 1/4 wave whip. Is the take off angle dependant on the capacitance hat. anybody ever try this?
thanks steve |
Bruce
Senior Member
Username: Bruce
Post Number: 4319
Registered: 9-2003
| | Posted on Wednesday, January 17, 2007 - 10:40 am: |
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if I remember right by removing the top hat it went up into the 10 meter band .... a 102 inch wip will make it go down in frequency .... |
Marconi
Advanced Member
Username: Marconi
Post Number: 681
Registered: 11-2001
| | Posted on Wednesday, January 17, 2007 - 1:08 pm: |
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Steve, if you check it out you will find that the AstroBeam antenna uses the AP antenna as a driven element. In that case the top is as you suggest, straight and it still is designed for 11 meters. I don't know the length, but the antenna doc's should indicate the length in that case.
The use of the cap hat is a design feature used to create a lower height by a few feet at the top of the antenna.
It is my opinion that the amount of horizontal material in the cap hat and the bottom loop may well help to produce a bit of horizontal polarized radiation, which may account for the reported excellent DX reports.
Why would you make the change? |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 31
Registered: 12-2002
| | Posted on Wednesday, January 17, 2007 - 2:27 pm: |
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thanks bruce thanks marconi, I'm apt to try to hotrod anything I can!! LOL. the top radiator and the cap hat are said to be equal in length electrically to a quarter wave. ive been reading here and there that if a coil or cap hat is introduced to an antenna for height reasons the performance will suffer. I thought maybe there was additional performance to be had by going with the steel whip in its place. ei. wilson 1000 vs. the steel whip. the 102 whip will win everytime, right? thanks again steve |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2362
Registered: 9-2004
| | Posted on Wednesday, January 17, 2007 - 4:56 pm: |
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it certainly is an original idea steve.
i didnt know that the top of the astroplane was equal to a quarter wavelength, but if thats the case, it might be worth a shot.
only way to see is to try it.
you might have problems getting the two to mate togehter, as the threads are metric in the new "top one" astroplane copy available today.
you might need to fabricate a custom threaded stud of some sort.
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 32
Registered: 12-2002
| | Posted on Friday, January 19, 2007 - 8:19 am: |
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I've been thinking, I'm going to leave the top one alone.......for the minimal gain i may see in the vertical radiation its just not worth it.
It is the best all around base antenna I've used. Less static than any fibreglass antenna.I've read 833's new antenna, very cool!!The part I found interesting about his antenna and the astroplane is the noticeable reduced pickett fencing. with the a99 the meter would dance around when talking to mobiles. with the top one, this is greatly reduced. not in signal strentgh , but the needle wavering and voice wavering on recieve. Like 833 would say "leave it alone and live happily ever after". thanks steve. |
Bluebird
Junior Member
Username: Bluebird
Post Number: 42
Registered: 2-2004
| | Posted on Tuesday, February 27, 2007 - 10:43 pm: |
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iam attempting to build an astroplane ,, i was wondering if there was a plastic sheild between the top radiator and the mast bracket,
Moderator Note!
It mentions a Black Plastic Insulator in the Original Assembly Manual for the Astro Plane AV-101 that I sent you.
Lon
Tech808
mitchell
bluebird
cef 398
cvc 113
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2427
Registered: 9-2004
| | Posted on Wednesday, February 28, 2007 - 12:41 am: |
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yes,
if you look at a pic of the antenna, where the coax connects to it, you will see that the shield goes to the big metal bracket that the mast attatches to; the center pin goes to the element pointing downward, which is also insulated from the mast bracket.
the center pin connection goes down that side of the antenna, around the hoop, and up the other side, to a nut that the top radiator screws into.
this nut is insulated by being seated in plastic.
the lower mast bracket is totally isolated from the rest of the antenna.
important things to remember about this antenna is the spacing between the downward elements, their lengths, and there must be a solid metal to metal connection from the mast to the top bracket, continuing down 8.5 feet past the hoop.
this means that you must scrape the paint off of painted mast sections where they meet, and where they would meet the antenna mast bracket.
run the coax right down the mast.
i think wildrat has built one of these before.
good luck, i would love to see some pics of the project,
matt |
Bluebird
Junior Member
Username: Bluebird
Post Number: 43
Registered: 2-2004
| | Posted on Wednesday, February 28, 2007 - 10:06 am: |
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thanks alot MATT,,i will try that. I will post pics when i get it made,,,thanks again
mitchell
bluebird
cef 398
cvc 113
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Tech833
Moderator
Username: Tech833
Post Number: 1614
Registered: 8-2002
| | Posted on Wednesday, February 28, 2007 - 10:25 am: |
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The top section is NOT insulated from the upper mast bracket. |
Marconi
Advanced Member
Username: Marconi
Post Number: 685
Registered: 11-2001
| | Posted on Wednesday, February 28, 2007 - 11:01 am: |
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Bluebird asks:
iam attempting to build an astroplane ,, i was wondering if there was a plastic sheild between the top radiator and the mast bracket,
and:
Kid Vicious states:
yes,
if you look at a pic of the antenna, where the coax connects to it, you will see that the shield goes to the big metal bracket that the mast attatches to; the center pin goes to the element pointing downward, which is also insulated from the mast bracket.
the center pin connection goes down that side of the antenna, around the hoop, and up the other side, to a nut that the top radiator screws into.
this nut is insulated by being seated in plastic...
Bluebird it appears there were several different AP antennas designed and built. I'm not sure I can electrically describe every one of these, but the one that I have has the insulator in both sides of the mast bracket and the Kid is correct with everything except that the insulator in the mast bracket opposite the feed point side does not insulate the radiator going up to the top from the mast bracket as he describes. The Kid uses the reference "a nut in the insulator" to describe that this part of the radiator is insulated from the mast bracket and that is just not the case.
I think this insulator was added to the AP later on in order to balance the mast bracket design which use to be two pieces (bolted together) with the side of the mast bracket in question being much smaller in order to directly hold and connect (no insulator) both the top and bottom elements on the side going up. Maybe this point might have been found to be a weak connection point and was changed in design.
I believe this point on the radiator is a current node so it makes no difference if it is grounded at that point or not. The magic of this antenna is in the feed point area and we cannot see it. |
Wildrat
Senior Member
Username: Wildrat
Post Number: 1250
Registered: 12-2003
| | Posted on Wednesday, February 28, 2007 - 1:56 pm: |
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I built one out of 5/8ths refrigeration copper when I was in Georgia. My boy's used the antenna on their base for several years before we moved to Florida.
SWR were very good and those boy's talked to everyone I did and my A99 was several more feet in the air.
WILDRAT
MARK
27.285MHZ
CEF674
CVC029
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2431
Registered: 9-2004
| | Posted on Thursday, March 01, 2007 - 12:20 am: |
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thanks for clarifying marconi!
marconi is right, as is 833 (of courseLOL), i was mistaken.
i forgot about that bolt that holds the nut i am speaking of in place. it goes right through the mast bracket, and thus is connceted to it, and therefore NOT insulated from it.
sorry, its been a while since i looked at mine up close. (hard to see that bolt up at 54' in the air!)
this raises one question for me; why is this piece made of plastic instead of just a solid piece of metal with threaded holes in the top and bottom?
what am i missing, and am i now correct about how the antenna is built?
sorry for the confusion.
matt |
Marconi
Advanced Member
Username: Marconi
Post Number: 686
Registered: 11-2001
| | Posted on Thursday, March 01, 2007 - 1:10 am: |
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I explained my reasons why that area might have been changed to plastic at some point.
"I think this insulator was added to the AP later on in order to balance the mast bracket design which use to be two pieces (bolted together) with the side of the mast bracket in question being much smaller in order to directly hold and connect (no insulator) both the top and bottom elements on the side going up. Maybe this point might have been found to be a weak connection point and was changed in design."
Additionally, it could have been changed for cost reasons.
Kid, it might be interesting to look closley at the Signal Engineering Quad feed system of feeding at a voltage node. For me, these two feeder methods seem to have similarities. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2434
Registered: 9-2004
| | Posted on Thursday, March 01, 2007 - 4:37 pm: |
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ahhh, balance marconisan! good point.
i will look at that feed system, as i need to start learning more about beams anyway. never really got into the theory much, because ive never had the room to put one up.LOL
matt |
Twixer
New member
Username: Twixer
Post Number: 1
Registered: 3-2007
| | Posted on Sunday, March 18, 2007 - 9:15 am: |
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A newbie here that just bought an Astroplane from Copper. This forum answered my question. I noticed the antenna was grounded to the mounting bracket by an allen screw. Didn't think this was correct and figured you removed the screw after assenbly,but I see it stays in place. Thanks guys for your help. |
Bluebird
Junior Member
Username: Bluebird
Post Number: 48
Registered: 2-2004
| | Posted on Friday, March 23, 2007 - 9:56 am: |
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My astroplane project is coming together,I am
not sure of the lenth of the mast bracket, I know the fiberglass spreader arm is 13". and is the spacing between them important? I want to thank everyone for the info,I would not be able to make this ant without it.
mitchell
bluebird
cef 398
cvc 113
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