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Thread: Weird China RF triggers

  1. #21

    Default Re: Weird China RF triggers

    Modified it with the antenna - works up to 40m, at 1/160s shutter. (I too lazy to walk and test beyond 40m). Below are some sample shots. Cheers!


  2. #22
    Member/Tangshooter zaxh81's Avatar
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    Default Re: Weird China RF triggers

    Nice mod,you really need a very long lens to shoot from that distance.

  3. #23
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    Default Re: Weird China RF triggers

    Quote Originally Posted by chanjyj View Post

    Your real one is what? Pocket Wizard, Bowens or Elinchrom?
    Yeah I switch to PW.

    btw the same mod I did and I coin up the antenna in line of sight, it can go very far like 100m.

  4. #24

    Default Re: Weird China RF triggers

    Quote Originally Posted by zaxh81 View Post
    Nice mod,you really need a very long lens to shoot from that distance.
    Argh. I guess my soldering skills not up to standard

    Blardy antenna just fell off

  5. #25

    Default Re: Weird China RF triggers

    Quote Originally Posted by chanjyj View Post
    Disappointed. After adding the extra antenna, (despite theoretical increased range of 30m), range remains the same and the furthur you go, the slower the flash responds. By the time I reach 11m, shutter speed has to be approx 1/60s (which means I cannot overpower the sun) and that is, if the stupid receiver fires the flash at all. (I would say failure rate of 50%).

    Any engineer here who can advise me on the antenna? I really at a loss now. According to science, I have already done everything right.

    (It is not the transmitter or receiver problem. I have already went to change for a new set. Problems are identical)

    How did you come to 5.5cm? A quick calculation for 433MHz would give a 17.5cm long quarter wave monopole. Then you'll need a large enough ground plane for it to work properly.

    Also, you do not know if there were already matching components on the board itself. If so, changing the antenna would require the matching components to be changed to obtain a better matching for your new antenna. So in fact, changing the antenna might only make the performance worse.

    You want it to be fast, use an optical slave. Set a triggering flash in a tele mode, use flash extenders (or maybe even a telescope?) with barn door to reduce the angle of coverage if required and point the optical slave at the flash. If need be, add some optics (telescope?) in front of the slave to make sure it is pointing to the trigger. I think you can get a very long distance with this kind of set up.
    Last edited by lsisaxon; 23rd January 2008 at 12:05 PM.

  6. #26

    Default Re: Weird China RF triggers

    Quote Originally Posted by lsisaxon View Post
    How did you come to 5.5cm? A quick calculation for 433MHz would give a 17.5cm long quarter wave monopole. Then you'll need a large enough ground plane for it to work properly.

    Also, you do not know if there were already matching components on the board itself. If so, changing the antenna would require the matching components to be changed to obtain a better matching for your new antenna. So in fact, changing the antenna might only make the performance worse.

    You want it to be fast, use an optical slave. Set a triggering flash in a tele mode, use flash extenders (or maybe even a telescope?) with barn door to reduce the angle of coverage if required and point the optical slave at the flash. If need be, add some optics (telescope?) in front of the slave to make sure it is pointing to the trigger. I think you can get a very long distance with this kind of set up.
    1/4*17.5. But I think I calculated wrongly - 4.37cm, not 5.5 cm. BAH.

    Nevermind - my modded RF trigger works darn well now. Optical slave cannot work for what I want, because at 30m plus distance it has to be line of sight already. If I am shooting from ground storey, then place a strobe at 5th storey pointing down, then another strobe at 1st storey pointing up, subject is on an elevated platform, there is now way both strobes can be triggered.

  7. #27

    Default Re: Weird China RF triggers

    Quote Originally Posted by chanjyj View Post
    1/4*17.5. But I think I calculated wrongly - 4.37cm, not 5.5 cm. BAH.

    Nevermind - my modded RF trigger works darn well now. Optical slave cannot work for what I want, because at 30m plus distance it has to be line of sight already. If I am shooting from ground storey, then place a strobe at 5th storey pointing down, then another strobe at 1st storey pointing up, subject is on an elevated platform, there is now way both strobes can be triggered.
    3x10^8/ 433 x10^6 = 0.7m

    0.7 / 4 = 17.5 cm

    Why did you divide by another 4?

  8. #28

    Default Re: Weird China RF triggers

    Quote Originally Posted by lsisaxon View Post
    3x10^8/ 433 x10^6 = 0.7m

    0.7 / 4 = 17.5 cm

    Why did you divide by another 4?
    17.5 too long so divide again - no choice

  9. #29
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    Default Re: Weird China RF triggers

    Quote Originally Posted by lsisaxon View Post
    How did you come to 5.5cm? A quick calculation for 433MHz would give a 17.5cm long quarter wave monopole. Then you'll need a large enough ground plane for it to work properly.

    Also, you do not know if there were already matching components on the board itself. If so, changing the antenna would require the matching components to be changed to obtain a better matching for your new antenna. So in fact, changing the antenna might only make the performance worse.
    It's also possible/likely to exceed the legal radiated power, or to transmit illegal levels of harmonics. Although I wouldn't be surprised if the entire set was illegal in the first place.

    Note that "improving" the receiver antenna also can cause (illegal) interference - low-cost UHF receivers actually radiate a bit themselves.

  10. #30

    Default Re: Weird China RF triggers

    Quote Originally Posted by LittleWolf View Post
    It's also possible/likely to exceed the legal radiated power, or to transmit illegal levels of harmonics. Although I wouldn't be surprised if the entire set was illegal in the first place.

    Note that "improving" the receiver antenna also can cause (illegal) interference - low-cost UHF receivers actually radiate a bit themselves.
    IIRC, those China made RF triggers are not IDA approved. On the other hand, PocketWizards are also not approved. So the lousiest are not approved, and neither are the best. What a joke.

    That leaves only elinchrom (I not even sure if Bowen is approved).

    Anyway back to point, I modded my transmitter a third time (I have never touched the receiver, only the transmitter. Modding the receiver means I have to mod ALL my receivers while modding the trasmitter means I only have to mod one), and this version 3 mod (using a small car antenna) has approximately the same range as an elinchrom (IDA approved). So the only think to look at seriously now is spillover, which I am not in a position to test.

    So... what the heck.
    Last edited by chanjyj; 23rd January 2008 at 09:47 PM.

  11. #31

    Default Re: Weird China RF triggers

    Quote Originally Posted by chanjyj View Post
    17.5 too long so divide again - no choice
    Wah.. you good.. If it were so easy, I would have been a photographer now because I won't be able to find an engineering job.

  12. #32
    vince123123
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    Default Re: Weird China RF triggers

    Just wondering, why would you ever need to shoot from a distance of 30-40m?

  13. #33

    Smile Re: Weird China RF triggers

    the brand is hovono or something like that?

  14. #34

    Default Re: Weird China RF triggers

    Quote Originally Posted by reachme2003 View Post
    the brand is hovono or something like that?
    It goes by many names.. some call it IMPACT, some call it RF 104, blah blah.. in the end it is the same trigger sold under different names

  15. #35

    Default Re: Weird China RF triggers

    Quote Originally Posted by lsisaxon View Post
    Wah.. you good.. If it were so easy, I would have been a photographer now because I won't be able to find an engineering job.
    Anyway there has been a modification 3 now. I replaced the whole thing with a short stubby $10 car antenna. I gave up figuring the range. Still works to approx 30m.

  16. #36

    Default Re: Weird China RF triggers

    Quote Originally Posted by vince123123 View Post
    Just wondering, why would you ever need to shoot from a distance of 30-40m?
    Concert Halls, put the strobes/flashes on upper levels and shoot down (alternatively, bounce em off the ceiling). Meanwhile, I am stationed at ground floor with camera.

    Another one is outdoor events at night, eg countdown party. Flashes will be placed around the event area, encircling it with light everytime I take a shot.

  17. #37
    vince123123
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    Default Re: Weird China RF triggers

    Hmm I see, you'll need one heck of a telephoto lens then

    Quote Originally Posted by chanjyj View Post
    Concert Halls, put the strobes/flashes on upper levels and shoot down (alternatively, bounce em off the ceiling). Meanwhile, I am stationed at ground floor with camera.

    Another one is outdoor events at night, eg countdown party. Flashes will be placed around the event area, encircling it with light everytime I take a shot.

  18. #38

    Default Re: Weird China RF triggers

    Electromagnetic waves move at lightspeed, the problem, as you found out, was energy, which you seem to have fixed with a higher gain antenna. Which model trigger is that anyway?

  19. #39

    Default Re: Weird China RF triggers

    Quote Originally Posted by jmmtn4aj View Post
    Electromagnetic waves move at lightspeed, the problem, as you found out, was energy, which you seem to have fixed with a higher gain antenna. Which model trigger is that anyway?
    the smaller brother of RF 616 (616 is 4 channel, mine is 2). I'm lazy to take out the duct tape again just to look at the model number.

    actually I'm abit confused. How does an antenna boost gain without drawing energy from the device?

  20. #40

    Default Re: Weird China RF triggers

    http://en.wikipedia.org/wiki/Antenna_gain

    What you did is basically how people boost transfer speed and connectivity at longer ranges with wireless routers- switching to higher gain antennas

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