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Thread: Crosshair - 10 dbic Circularly polarized antenna tutorial!

  1. #121
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    Here is my attempt at a 1280Mhz crosshair. I used a 8x8 reflector mounted on a patch antenna front cover (perfect fit). I then encased the whole front in black Depron foam and covered in packing tape. Sorry I forgot to take pics of the inside. Everything was cut to IBCrazy's formulas using digital calipers. Initial ground test are too good. I can't point the antenna where it doesn't get a perfect signal even through brick walls. I will have to test more, when I can get out and do a proper test.

    Click image for larger version. 

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    I think I'm gonna smash this VTX with extreme prejudice!! [B]KK4HBG [/B]

  2. #122
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    Just FYI 8*8 won't give you 10dbi. I forget what Alex said it actually was, 9 I think. Should still perform very well.

    Marc
    [QUOTE=whakahere;63562]I keep thinking I should give up crashing too ... I guess it is an addiction.[/QUOTE]

    [QUOTE=CaliDave]Who sliced open that tauntaun?[/quote]

    Me----"This is a results may vary type of hobby, get used to it."

    Video Aerial Systems Operations Manager

  3. #123
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    Quote Originally Posted by MASHTON1138 View Post
    Just FYI 8*8 won't give you 10dbi. I forget what Alex said it actually was, 9 I think. Should still perform very well.

    Marc
    Yes I wanted a little bit of side and back lobes. Plus I had a 8x8 sheet of aluminum laying around. I wish I would of took pictures, because I made a bolt on balun. Soldering on aluminum is almost impossible.
    I think I'm gonna smash this VTX with extreme prejudice!! [B]KK4HBG [/B]

  4. #124
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    Well, I just read through this and I think I'm going to take a crack at making mine tomorrow night. After my experience with the CL/SPW combo, I am very excited about the performance of this one.
    KF7TRU, [COLOR="blue"]youtube.com/user/wildwill1970/videos[/COLOR], Skywalker 1680mm, RMRC 400mW 1280mhz vTx, Dragonlink V1, MFD ATT, Crosshair GSA 1280mhz

  5. #125
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    HI dude, Im Newby from Korea.
    Um I'd like to ask something about antenna.

    I plan to make a 2510Mhz Crosshair Antenna.

    following is my calculation (2510Mhz)
    Wire diameter =0.425mm~0.607mm
    Height over reflector = 23.78mm
    Length of copper tube = 29.68mm
    Size of reflector panel = 89.05mm~177.09mm
    Short leg length = 25.198mm
    Long leg length = 29.802mm

    BTW in the following picture, Im wondering.
    Is 'Height over reflector' means "C" or "B-A"??
    Is "A" should be about 1/16"?

    Click image for larger version. 

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    If B=Length of copper tube=29.68mm and A=1/16" ,Height over reflector=29.68-1.588=28.092(in geometry) but my caculation is not same.(23.78).

    what is the problem with my point.

    Please let me know as soon as possible, Im dying to Flying my airplane stuff dude.

    Thank you so much.

  6. #126
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    Quote Originally Posted by k6821340 View Post
    HI dude, Im Newby from Korea.
    Um I'd like to ask something about antenna.

    I plan to make a 2510Mhz Crosshair Antenna.

    following is my calculation (2510Mhz)
    Wire diameter =0.425mm~0.607mm
    Height over reflector = 23.78mm
    Length of copper tube = 29.68mm
    Size of reflector panel = 89.05mm~177.09mm
    Short leg length = 25.198mm
    Long leg length = 29.802mm

    BTW in the following picture, Im wondering.
    Is 'Height over reflector' means "C" or "B-A"??
    Is "A" should be about 1/16"?

    Click image for larger version. 

Name:	tger.jpg 
Views:	649 
Size:	19.8 KB 
ID:	7955
    If B=Length of copper tube=29.68mm and A=1/16" ,Height over reflector=29.68-1.588=28.092(in geometry) but my caculation is not same.(23.78).

    what is the problem with my point.

    Please let me know as soon as possible, Im dying to Flying my airplane stuff dude.

    Thank you so much.
    I understood

    sorry ^^

  7. #127
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    You have the idea. The tube must protrude through the back. The tube is longer than the element height so there is no other way to do that.

    Element height is "C"

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    [url]videoaerialsystems.com[/url] - Performance video piloting

  8. #128
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    Quote Originally Posted by IBCrazy View Post
    You have the idea. The tube must protrude through the back. The tube is longer than the element height so there is no other way to do that.

    Element height is "C"

    -Alex
    Does the rear protrusion matter? My element height is correct but the tube is shorter than the recommended size because it doesn't protrude out the back far.
    I think I'm gonna smash this VTX with extreme prejudice!! [B]KK4HBG [/B]

  9. #129
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    Madison Heights, VA
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    "Install the copper tube so it protrudes through the back of the panel. Because the tube is longer than your element height it must protrude through the back some. The measurement from the top of the tube to the base of the reflector should be about 1/16” less than your height so your elements can clear it."

    So yes if using the balun method the tube must protrude. The tube is basically 1/4 wave length.

    Marc
    [QUOTE=whakahere;63562]I keep thinking I should give up crashing too ... I guess it is an addiction.[/QUOTE]

    [QUOTE=CaliDave]Who sliced open that tauntaun?[/quote]

    Me----"This is a results may vary type of hobby, get used to it."

    Video Aerial Systems Operations Manager

  10. #130
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    Dec 2011
    Location
    Utah USA
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    Very impressed with IBCrazy and Hugo and their willingness to share with the FPV community. I was hoping to upload a .xls spreadsheet that has quick calcs for the frequency you input, but can't see a way to get the xls file here. If someone likes to have the calculations file, PM me or maybe another will have a way to make it available to all. Here is what it looks like so far, the yellow blocks are for you to input your particular frequency. There were lots of calculations but are all removed in this text only upload.
    mmmmmmmmmmCh1
    9101280244157055705
    Wire Dia Min1066.81.17230.83340.4370.187
    Wire Dia Max15241.67471.19060.62430.26710.26
    Height over refl.5969065.59346.63324.45310.46310.4
    Length copper tube7449881.86658.20230.5213.05813.05
    Size refl panel Sml223520245.63174.6391.56939.1812000
    Size refl panel Lg444500488.46347.27182.177.91453.4
    short leg length6324669.50149.41125.9111.08611.08
    long leg length7480382.20158.4430.64413.11213.11
    Posts from center4572050.24235.71918.738.0148.01402
    Rules 13, 16, 33, 40, 44, 59, 76, 82, 94, 97, 111,211, 218, 242.
    But most of all RULE 117: "You can't free a fish from water."

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