Downlink Antennas?

Discussion in 'Video Assist & Video Accessories' started by Josh Lambeth, Jul 22, 2012.

  1. Nick Kolias

    Nick Kolias Moderator
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    Hey Andy, sorry I missed your question earlier. Ideally the transmit and receive antennas are oriented the same way to maximize range. The way I've mounted mine is a compromise but it's been that way for a while and we've been getting good results. It's only when I push the distance past 1500' that it starts to get dicey but it's rare I fly so far away. I'm also running two 5.8 channels which adds to the challenge. The video quality really is impressive with these things. For a crappy SD signal it actually looks decent even in a smallHD or 17" production monitor. Stedicam guys would have died for this even five years ago. :D

    nick
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I'm not enough of an antenna guru to know whether Gary's two different antennae are 100% compatible with the single TX antenna, so I chickened out and use two of the 4-lobe Bluebeams on the RX and single 3-lobe on the TX.
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hey no sweat. I almost missed your answer! :)
    Yeah, I'd think the range would be better if the antenna on TX and RX were symmetrical.
    Thanks for also answering a question I didn't even ask, but wanted to -- which was, "I wonder whether I can get two 5.8Ghz rigs working on the same bird?" (Obviously set to different channels...)
    I really am impressed by the quality of the video coming off the Sony CX760 composite video through 5.8Ghz Mondo Stinger/Passport down to a Small HD DP6 (which are pretty nice mtr's by the way).

    I've also upgraded my FPV camera to a WDR770 (700 lines). The Smart OSD works with it, but the picture quality is noticeably improved and the color saturation is much better. I've configured the Smart OSD to have several different screens -- one of which is "all flight critical data" -- a bit cluttered, through to "no on-screen data" just so I can see the entire view.

    As an aside, I discovered if you try and add the BL-Ctrl data to the Smart OSD, it bricks the SOSD board -- it just flashes the company name and firmware version number. The workaround is to remove the BL-Ctrl icons from all screens and re-send the screens and it unbricks the SOSD board. (Note: it may be that it's not the BL-Ctrl data, but a combination of that and something else...but it's sure as hell deterministic -- I can brick/unbrick at will.)

    Thanks
    Andy.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Well, when Tabb comes out with a radar altimeter, we can use that to disable the Radian pan module and disable the motor safety switch, right, Tabb? I suppose we could do it now with an aneroid altimeter, come to think of it. Or use the altitude data from the GPS? Or even an downward pointing ultrasound sensor that could act as a ground proximity sensor.

    Andy.
     
  5. Nick Kolias

    Nick Kolias Moderator
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    A radar altimeter would be pretty sweet! I looked into one with the hopes we'd have better altitude data than what the MK pressure sensor provides on the SOSD. Would come in handy for those low, surface skim shots. My hopes were crushed however- costly little sucker and I don't have the knowledge needed to integrate it into the system. But Tabb and the R&D team.... :D

    I'm using the same WDR770 cam for FPV. Very good image for its size. Great combo with the SOSD overlay. Funny you mention it because I too have a comprehensive screen for one configuration and a blank screen for another. Sometimes you just want to see the camera output and nothing else. The two 5.8 channels work well. I've spaced them as far apart as the channel assignments allow. And I'm using right hand polorization for one channel and left hand for the other to further encourage them to get along. :cool:

    nick
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Should we engage in the process known as "ratification of rumor?" As in, "I've heard there X is developing a radar altimeter." OK. That's the rumor started. Let's see how it plays out from here.

    An alternative method might be to use some kind of downward looking autofocus system be it optical or ultrasound -- point and shoots and smart phones do it pretty effectively now and we really only need a "you're less than six (or three) feet from something directly below the copter" to configure for landing (pan module off, motor safety off, stow antennae, camera gimbal horizontal, and brace for impact).

    As you say, some of those low altitude passes can really become quite scary on altitude hold. I find I fly them on FPV better than rely on AH, but it's, errr..."tense" and "colorful."

    Did you stick with the stock lens for the WDR770? I'm going to try a wider angle lens because the stock lens with 92 degree FOV feels a little blinkered.

    Thanks for the idea re: left/right polarization, Nick. As I'm not an antenna guru I don't know the degree to which opposite polarization causes appropriate signal rejection, but, as we say in the software business, "it should work." ;)

    Andy.
     
  7. Nick Kolias

    Nick Kolias Moderator
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    Using different polarization for the two channels is something I gleaned from others on the forums. With so much RF so close together it seemed like a good idea and it does seem to work.

    I did install a different lens on the 770. I forget what the focal length is but it gives me a field of view around 127°. I like to see around. :D
     
  8. Gary Haynes

    Gary Haynes Administrator
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    Andy

    The 'father' of the BluBeams is the one that recommended using the two different antennas on the receiver, one of the 4 lobe BluBeams and the 4 lobe fan antenna from the guys up north. There is a technical reason why the transmitter is a 3 lobe and the receiver is a 4 lobe. But when you buy a set that is exactly what you get.
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks, Gary. Who are the "guys up north," please?
    Google knows about these guys: http://videoaerialsystems.com/products/transmitter-antennas/

    I think I better buy some LHCP antennae as the Bluebeams are RHCP.

    Nick: I went with the 2.9mm lens -- which is the one that gives 127 degrees FOV, I think. Just bought one to try.

    Andy.
     
  10. Gary Haynes

    Gary Haynes Administrator
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  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Oh, the guys out East! (I'm in Portland, OR). ;)
    Thanks
    Andy.
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Actually, it turned out that the fan antennas come from Hugo Chamberland at hugo@truerc.net (http://www.truerc.net/) up in Quebec. He takes custom orders so you can ask, for example, for a 90 degree connector and any particular length of cable. He doesn't use the semi-rigid cable that you find on BlueBeams but uses RG-316 coax and then places a plastic tube over the coax to hold it straight.

    Thanks for getting me on the path to him, Gary.

    Thanks
    Andy
     
  13. Dragan Radoicic

    Dragan Radoicic New Member

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    I see I'm not the only one having antena problems. I've had problems with antenas for a long time until I switched to clowerleef. First I had Chinese 500mV Tx &Rx with regular omni antenas, I was able to cross the street and I would start to get interferance. Later I've ordered 1200mV dual Tx &Rx and still did not get few miles as advertised. Once I've made clowerleef omni antenas per "ICBcrazy-alex" tutorials i was able to eliminate interferance but still could not fly beyond 500-600 M. Later Ive ordered video Rx CP 5 turn directional antena and it did solve a lot of my frustrations. I dont have groundstation that folows aircraft so my camera guy needs to turn antena manualy.

    I've just ordered new type of antena from Hugo that should solve our problems. ( http://www.truerc.net/canada/index.php?main_page=product_info&cPath=30_49_50&products_id=214 ). I'll let you guys know once I test it.

    One thing I am still not clear, where is the best location on the copter to place video antena? Most of our components are made from carbon fiber and in most cases two Rx for commands and gimbal. I'would love to see your solutions!
     
  14. Matt Barker

    Matt Barker Member

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    I just got a set of bluebeam omnis for 1.280Mhz lawmate FPV system. This things are gigantic. I have no idea where Im going to put these. I'm hoping to run the 1.3 for fpv, 5.8 for long-range camera, and 60Ghz for short-range HD, and two 2.4 rxs. Too much going on?
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The Bluebeam 1.2Ghz are large. I put mine on top of a 10" semi-right cable so that it's elevated about 8" above the battery plate. I use a cable tie around one of the battery posts to it cannot flop over and stuff the antenna in to a prop. Actually, that should be: "and stuff the antenna into a prop again!" :( See the image below -- sorry if this appears to be rotated 90 degrees. It looks fine in Photoshop and Mac Preview, so I think it's a problem with the forum software....

    Be sure to put a low-pass filter on the 1.2Ghz as the first harmonic is 2.4 Ghz, but other than that "it should work."

    Hope this helps
    Andy.

    Blue beam 1.2Ghz.JPG
     
  16. Philip Ellerbroek

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    Per @Gary Haynes..... He's running Mondo Extremes 1.5w 5.8ghz down to 5.8ghz Diversity receiver. He was nice enough to send me these pics...

    I'm running a similar set up..... A Mondo Extreme 1.5w 5.8ghz to a DSLR feeding down to a Yellowjacket USB 5.8ghz Diversity and then i have a small FPV pilots camera on boom 1 that feeds into a second Mondo Extreme 1.5w 5.8ghz to a Passport 5.8ghz Diversity receiver.

    I ordered the Bluebeam 3 and 4 lobes from Readymaderc.com and then for the special fan antennas I placed an order from truerc.com Everything came in the mail yesterday and I'm installing tonight, hopefully testing tomorrow.

    Phil
     

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  17. Philip Ellerbroek

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    New setup... On the receivers the left side is a 4 lobe Bluebeam clovers from Readymaderc.com, while the right side is the fan from Truerc.com

    On the Mondo Extreme is the 3 lobe Bluebeam clover from Readymaderc.com
     

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  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Phil:

    Are you using the FPV-Japan DVR? Have you had situations where it just hangs while it's recording? The only way to un-hang is to pull the battery -- which also means you lose the recording of the flight.

    Also, I discovered in the documentation the other day, that you can turn off the icons it superimposes on the FPV footage if you press the Esc button after you've started recording. I've not tested that yet...

    Andy.
     
  19. Philip Ellerbroek

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    Andy,

    No, I'm not. Don't know much about it....What can you tell me about it?

    My cameraman is on Vuzixs and I have a 10" 12volt monitor.

    For portability and function, I'd like to end up with the the military version of the Vuzixs so you can have FPV and line of sight flying all in one for the pilot. $3k though.

    Would you be interested in investigating tearing a Vuzix 1200 pair apart, each guy getting a monitor for an eyepiece? That would be about 25% of the cost. Maybe with your electronic skills you could figure how to emulate without paying $6000 for two pairs ($3000 x 2)

    Here's what I'm speaking of..... http://www.vuzixtdg.com

    Im guessing for this project, signal and voltage would have to be altered/dropped for one eye piece vs. dual.

    PS - I'll keep you posting on the qc3328 making noise and if I'll be sending it your way for audio analysis.

    Phil
     
  20. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Oh...it looked like you have a small DVR in the lower left of the image. Not much to tell except that's small, low cost and has the advantage of a video pass-through so you can avoid blue-screen on loss of video sync -- it just shows static but regenerates the sync for the monitor.

    Yeah. Those would be nice.

    Well, tell the truth my electronic knowledge is not that good, I'm afraid. Worse yet, I'm in the middle of a DVD production and have a list as long as your arm of things I need to do on my aircraft before the rain stops in Oregon (which is scheduled to be around July 2013!)

    Thanks!
    Andy.
     

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