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Thread: Introducing the "Vulcan"

  1. #21
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    I usually fly on 1360 since a year ago somebody put up some kind of rotating beacon that trashes 1280 video across the entire state. My crosshair works great on level ground, but flying in the mountains is hit and miss. Colorado's mountains have a very high metal content, which tends to cause lots of signal reflections. I can be flying about 2 miles away in front of a peak, 3000 feet above my ground station with direct line of sight and the antenna aimed right at the area where the plane is, and I'm flying in and out of tons of static. Usually happens either directly in front of a mountain, or right over a ridge line. The worst is when I'm in front of the mountain and down in a bowl-type area, where I still have clear LOS to the plane, but the mountain wraps around to the side towards my launch site.

    It kind of concerned me at first since I had read crosshairs were supposed to be really good at multipath interference. I've since just learned to live with it. But my goal is to do more and more mountain missions, and it would be nice to be able to cut down interference. Could I perhaps have a defective crosshair? I have noticed that the wood plate the reflector is mounted on is a little warped (probably my fault for storing the antenna in a backpack). Don't know if that would affect it.
    Last edited by prelator; 11th March 2014 at 10:25 PM.
    ~Patrick M.

    YouTube Channel: youtube.com/user/SerithianFPV

    Colorado FPV Pilot and Flying Site Map: mapsengine.google.com/map/edit?mid=zjYlxx5w300I.kmgDGKOhrMAo

  2. #22
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    Click image for larger version. 

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    This is a simulated freq. sweep from a 1280 crosshair, you can see an axial ratio at 1280 of 0.99, but quickly drop to below 0.4 at 1360.
    I think a custom made crosshair will help you there.

    -Hugo

  3. #23
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    Ahhhh. So a higher axial ratio has better multipath rejection? I guess that explains it then. So I either need to use 1280 like the antenna was designed for, or get/make a crosshair tuned to 1360. Interesting.

    I should do an experiment next time I fly. I'm temporarily living in Boulder and have been flying along the Flatirons, and there are several places that reliably cause lots of static. I should try flying on 1280 and see if it's better. The problem is this beacon or whatever causes a burst of static every 12 seconds that thrashes your video signal for a second. We think it's based in Denver so it's not so bad in the mountains, but I've seen it even as far away as South Park, which is over 100 miles away and across the continental divide from Denver.

    I'll have to play around with frequencies more, and maybe learn how to build by own crosshair since you can't buy them tuned to 1360. Thanks for your help!
    ~Patrick M.

    YouTube Channel: youtube.com/user/SerithianFPV

    Colorado FPV Pilot and Flying Site Map: mapsengine.google.com/map/edit?mid=zjYlxx5w300I.kmgDGKOhrMAo

  4. #24
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    Hugo, is that plot from 4NEC2? How do you plot axial ratio like that?

    Patrick, I'm not entirely certain that the "12 second signal" on 1280 still exists. I think it was probably a temporary additional aircraft radar during the fire season.
    youtube.com/secretspy711
    [COLOR="#ff8c00"][B][COLOR="#696969"]CO[/COLOR]FPV[COLOR="#4169e1"].com[/COLOR][/B] [/COLOR]

  5. #25
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    Quote Originally Posted by prelator View Post
    Ahhhh. So a higher axial ratio has better multipath rejection? I guess that explains it then. So I either need to use 1280 like the antenna was designed for, or get/make a crosshair tuned to 1360. Interesting.

    I should do an experiment next time I fly. I'm temporarily living in Boulder and have been flying along the Flatirons, and there are several places that reliably cause lots of static. I should try flying on 1280 and see if it's better. The problem is this beacon or whatever causes a burst of static every 12 seconds that thrashes your video signal for a second. We think it's based in Denver so it's not so bad in the mountains, but I've seen it even as far away as South Park, which is over 100 miles away and across the continental divide from Denver.

    I'll have to play around with frequencies more, and maybe learn how to build by own crosshair since you can't buy them tuned to 1360. Thanks for your help!
    Give Mashton1138 a shout, he may be able to help you out.
    http://fpvlab.com/forums/showthread....by-Mashton1138!
    When nothing else out there will suit your needs... design and build it yourself.

  6. #26
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    Quote Originally Posted by prelator View Post
    Ahhhh. So a higher axial ratio has better multipath rejection? I guess that explains it then. So I either need to use 1280 like the antenna was designed for, or get/make a crosshair tuned to 1360. Interesting.

    I should do an experiment next time I fly. I'm temporarily living in Boulder and have been flying along the Flatirons, and there are several places that reliably cause lots of static. I should try flying on 1280 and see if it's better. The problem is this beacon or whatever causes a burst of static every 12 seconds that thrashes your video signal for a second. We think it's based in Denver so it's not so bad in the mountains, but I've seen it even as far away as South Park, which is over 100 miles away and across the continental divide from Denver.

    I'll have to play around with frequencies more, and maybe learn how to build by own crosshair since you can't buy them tuned to 1360. Thanks for your help!
    You can always trim down your crosshair to fit 1360MHz. Center to end of long element: 2.16". Center to tip of short element: 1.83"

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

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

  7. #27
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    Quote Originally Posted by SecretSpy711 View Post
    Hugo, is that plot from 4NEC2? How do you plot axial ratio like that?
    bump. pretty please HugeOne? My plot of the crosshair Alex sent me doesn't look like that, I can't figure out what settings aren't right.
    youtube.com/secretspy711
    [COLOR="#ff8c00"][B][COLOR="#696969"]CO[/COLOR]FPV[COLOR="#4169e1"].com[/COLOR][/B] [/COLOR]

  8. #28
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    hi hugo, i understand these are special order. whats the lead time to get one made? thanks, joe

  9. #29
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    Sent PM

  10. #30
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    Quote Originally Posted by ChrisG View Post
    Hi all,

    Just got my Vulcan braced up and mounted on its tracker after it's long journey from Canada to Oz... I'm very happy with how it turned out.
    It was a little flimsy for my tracker mount so I braced it with depron and Balsa, had to keep weight down as I'm already running a near 2lb counterweight to help the tilt gearbox out.

    Testing it out tomorrow, have a range flight planned for sun but weather forecast is not looking very good at the moment.

    Thanks again for making this for me at my freq Hugo.... Really appreciate it mate.


    Edit... Not sure what's going on with attachments, they are all the same orientation in my phone.
    hi chris, love your setup. i just picked up the same servocity pan/tilt. i see your using a counterbalance and curious what the weight is. thanks, joe

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