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DCSensui

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About DCSensui

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    RC-Cam Visitor
  1. Here's something that converts analog to Firewire: http://www.bhphotovideo.com/bnh/controller/home?O=WishList.jsp&A=details&Q=&sku=312315&is=REG Grass Valley ADVC-55 Analog to Digital Media Converter Price is about $150.
  2. I just noticed this and want one, too.
  3. DCSensui

    FVP and Insurance

    Maybe have a few "barf bags" available, just in case? :-)
  4. Makes sense to do that. With full-scale aircraft, the antenna for the radar transponder is placed below the fuselage so the ground-based ATC receiver can "see" the transponder with less chance of the aircraft's structure blocking the signal.
  5. Yeah, I'm wondering if the counterpoise being that close to the tail fin might have an adverse effect. If it's a problem I'll have to make a Plexiglass version of a tail fin. At least the tail rotor blades are transparent to radio waves.
  6. So here's the actual "flying" version of the antenna. The elements consist of brass tubing with a diameter of 0.9". The length of the elements are 3.09", measured from where the conductor emerges from the ferrite bead. The brass elements are supported on a plastic base with tiny Plexiglass blocks. A quick range check -- almost line-of-sight -- got me 1/10 mile before the image started to break up a bit. I'm not sure how good the receiver antenna works since it's another crudely cobbled setup. Here are the basic parts. The mounting blocks are tiny Plexiglass strips that were drilled to fit the brass tubes. The brass elements were soldered to the conductors, then slipped into the Plexiglass blocks. That eliminated the concern of possibly damaging the blocks with any excess heat. Here's the antenna on the tail. The idea is to have the radiating element clear of any obstructions, away from the RC receiver, and away from the main rotor blades. This is the finished project with the antenna mounted on the tail of the TRex 450.
  7. Correction: I had it set at 3.12" Thanks again for your calculation.
  8. Thanks for the suggestions. This was the "stock" antenna that comes with the transmitter. And it was connected directly to the transmitter as seen in the photo, except that it was pointed downward instead of upward. I've read elsewhere that the stock anteanna can be pretty bad with a reported SWR of 3:1 or so. And pivoting the antenna 90 degrees can make it even worse. The thought behind the solution that I'm cobbling together is to get the antenna way back on the tail, away from the R/C receiver and away from the rotor blades.
  9. I got the length from an online calculator. Thanks for the corrected figure. Would both elements have to be trimmed? Or is the "ground" half of the element less critical? Regarding the metal fences, etc., I noticed something quite interesting. Doesn't take much to foul up a signal. I noticed that the receiver antenna could find tiny dead spots that were about four inches in diameter, and I could actually blank out the signal if I carefully placed the antenna in just the right spot, even though the polarization was correct. And if I used the metal body of my iPod Touch like a mirror, I could interfere with the signal significantly. Anyway, my 4-year-old granddaughter was asking about what I was making, and found it intriguing that you could get a live video signal from one point to another without any wires in-between. Thanks for the guidance!
  10. I finally got the ferrite beads and assembled a very crude dipole as a test. It's an RG-174 wire with a right-angle SMA connector. The ferrite bead sits right where the dipole starts. The center conductor is soldered to a short length of wire as is the shield. Both wires were trimmed so the length of each element is 3.2", measuring from point where the elements start at the ferrite bead. Everything was mounted to a piece of scrap plexiglas. Totally unflyable but it's just a "breadboard" version. I don't have any test equipment except a digital thermometer that I checked by immersing it in ice water to check for accurate freezing point, then boiling water to check that, too. Both were within 0.5 degrees. Ambient temp was 75 deg F (it's winter here in Hawaii). No wind in the enclosed garage. With the stock Range Video antenna in a normal operating position (bent 90 degrees toward the ground), the temp got to 127 deg F in 10 minutes. I had the helicopter suspended one foot off the table on a wood block. With the crude dipole the temp got to 118 deg F after 20 minutes. Someone said that temperature might be a rough indicator of antenna efficiency or SWR? If there's a correlation, then perhaps this might provide some performance improvement over the stock antenna?
  11. VHB isn't a garden-variety double-sided foam tape. This is an industrial product that's used in critical applications. So if it's applied to a properly cleaned surface, it'll stick extremely well. Among the applications include glass windows in high rises and certain aircraft components. I did a quick Google search. Apparently I saw a story about VHB on Modern Marvels: VHB is discussed at the 1:14 mark. Another video that compares VHB to conventional double-sided tape: A company like 3M wouldn't encourage its use in critical applications if it didn't work nearly perfectly: that would expose them to huge liabilities.
  12. DCSensui

    Show Us Your Fpv Platform!

    It reminds me of that martian character from the Bugs Bunny cartoons!
  13. I was using the "stock" Range Video antenna but read that it's not very efficient, and it gets worse when it's bent 90 degrees. I'm going to try a dipole that's in a better location and possibly more efficient. Here's how I had it set up. Unfortunately there's a lot of junk directly in the radiation pattern (tail boom, servo). It also works angled downward with the standard landing skids. Edit: by the way, the transmitter's attached with something called 3M VHB tape. 3M developed it to fasten windows and other high-stress, critical materials. I believe it was used to mount the glass on a high-rise in Saudi. I saw a story about it on the Discovery Channel and found this stuff in Radio Shack. It requires an overnight set to attain full strength, but once it does, it's really stuck. Yet you can cut it free with a razor blade. It tolerates heat and moisture. A tiny strip was all that was needed to bond the transmitter to the carbon fiber rods.
  14. Thanks for the info, Terry. I hope to be able to get a few of the right type of ferrite beads. Apparently they're designed for specific frequency ranges. I'll give this a try and see how it goes. Dean.
  15. I'm new to this forum but have been lurking all over the place researching antenna information. Seems like each discussion forum has its specialties with great experts, and this is the one for transmitters and antennas. Thanks for sharing all the knowledge and experience! I'm considering making a dipole antenna for a 500 mw, 900 MHz Range Video transmitter, to be mounted on an Align TRex 450 helicopter. I wanted to place the antenna way back at the tail rotor, out of the way of the main rotor blade. An RG172 cable leads to the antenna. Attached is a crude diagram, not to scale. It shows the cable, a ferrite bead at the junction where the coax joins the dipole, and how the radiating/ground elements attach to the coax and shield. Would this work? Would the helicopter's carbon fiber tail be a problem if it's adjacent to the ground half of the dipole? I thought an appropriate ferrite bead would act as a choke. Fair-Rite has a ferrite bead that's designed to work within the frequency range of 250-1000 MHz. Would I need more than one of these? Or would it be needed at all? Weight, of course, is a concern this far back on a TRex 450. Needless to say, I don't know a whole lot about antennas and don't have any equipment to measure SWR, radiation energy, etc. With a helicopter this size it's difficult to place an efficient antenna without it being at risk of getting hit by the main rotor or having to sit at some odd angle to prevent it from interfering with landing gear, etc. Many thanks in advance. Dean.
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