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Figured I'd say hi

Discussion in 'Introductions' started by VenomBallistics, Aug 30, 2018.

  1. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Clearly, much more investigation is required before jumping into any sort of multiplexed, single-channel, duplex communication scheme. You are absolutely correct in your observations about propagation through vegetation, such as trees, being affected by frequency. I had not considered that a problem if using amateur radio frequencies and allowable amateur radio power levels, but of course it is, especially as you move higher in frequency. You mentioned in another post using lower frequencies (900 MHz) to propagate around or through obstacles, but that isn't always practical either because of size, weight, and power (SWAP) constraints.

    I don't think it is either necessary or desirable to separate the command/telemetry functions from the video/still-image functions and use separate frequency spectrum for each, but this is apparently current practice, and it was not by design. Instead, existing control and telemetry technology using one part of the radio spectrum was paired with later video technology that "happened" to use a different part of the radio spectrum. So we are stuck with it for now.

    There is a lot of unused bandwidth available "between the lines" of even HD video, and breaking data up into digital packets with cyclic redundancy check characters, and error detection and correction using a duplex communications link, is standard practice for Internet Protocol packets... otherwise you would never be able to transmit files without corruption or loss of data. Of course a "noisy" path with lots of packets that need to be re-transmitted is going to degrade latency and introduce an undesirable delay, but with sufficient power and bandwidth even that can be mitigated to allow real-time radio control. The axe and mop approach, so-to-speak.

    I have done some more reading about UAV operations. It appears that FPV control is the wave of the future that some operators or pilots may now be surfing (illegally) as we speak. There are procedures in place to request and obtain FAA exemptions from the line-of-sight visibility, 400 foot ceiling above ground level, and 100 mph speed limitations for those pursuing a non-hobby FAA drone licensing path. Unfortunately, I have no idea how often, or under what circumstances, such exemptions are granted, but it seems like a lot of hoops to leap through just to fly an airplane with FPV visualization. I suspect there are a LOT of UAV pilots that are ignoring the FAA line-of-sight rules. If so, they would certainly need a reliable radio link to do this. If this high-quality link were to be enabled by an FCC licensed amateur radio operator, that operator would have to also abide by the FAA rules and regulations and obtain an exemption to the line-of-sight rule before flying off into the wild blue yonder to escape the surly bonds of Earth, and maybe touch the face of God. (Apologies to John Gillespie Magee Jr.)
    Roger, that. Can't legally do FPV flight control over long distances either. Guess I should apply for a drone pilot license and then ask the FAA for a line-of-sight exemption. Ever heard of anyone doing that? I don't want to lose my amateur radio license because I violated an FAA rule or regulation.
     
    Last edited: Dec 16, 2018
  2. Hopup

    Hopup

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    Jul 5, 2015
    Honestly, its not going to hurt anyone by using little bit more power on the 5.8Ghz bandwidth and I doubt anyone will really even care if you use 500 to 1000mw or even more. Other frequencies might be different thing since they are used for all kinds of avionics etc applications which might be actually disturbed by your signal.
     
  3. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    yes .. for now, a great many things occur outside the constraints. The FAA drafted their regs listening to CNN, Google and crybabies rather than the AMA. I'd say that easily 15% of all model airplanes can exceed 100 MPH. this has been the case since the late 1900's
    race quads enjoy a higher concentration of 100 MPH + machines as well. It's just not a practical limitation.
    400 feet ... we actually try to abide by this, it nests into long standing private pilot regs. We even drop altitude below 100 feet in the presence of full scale craft.
    I guess they are working on a revised special rule for RC ... perhaps it'll contain less navel gazing than current. Our situational awareness meets or exceeds that of a full scale flight with current FPV gear, so I expect that to change at some point.
    The bulk of the problem is due to hype over a few avoidable incidents.

    Now the main reason for a two band approach is a brand protocol kind of thing. Taken individually, I have no doubt that any given brand of radio could be multiplexed into extremes beyond any proposed need. The issue is that a Spektrum DSMX system does not play the same tune as a Futaba FASST system, or a FrSky ACCST.
    While in each case, the same data goes in at point A and the same result comes out at point B You have to match the color of the ink between em. Thus, it's never been a practical idea from a product perspective. You're doomed to catering to a single system, or offering a product array too vast to sort out for most users.

    FAA part 107 ... yeah .. we have a few in my club so licensed.
    The rules are in flux right now. the FAA may work around something closer to reality in the next drafts.
    Our current work around is to have a spotter keeping visual on the craft. Now that might be spec out on the horizon ... but a visual is a visual.
    To take this a bit further, someone somewhere can see it, thus you always have a spotter, and if not, no witness ... no crime.
    This also illustrates the vital need to sort out this trainwreck legislation.

    Aside from unreasonable laws that need revision to comply with the laws of physics as they apply ... we do strive to work within the law as much as we can. Just 5 years ago, none of these issues were even issues and simple guidelines set forth by the AMA were sufficient to avoid any issues. The only laws that existed for our violating pleasure were FCC. Most of us strive to comply to them.
     
  4. Faraday's Cage

    Faraday's Cage

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    Mar 21, 2019
    Sorry to bump an old thread, but I was just engaging in some internet archaeology and when I noticed that DF was down I found this through Google. Good to know at least some of the guys are still talking somewhere :)
     
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Welcome to Electronics Point, @Faraday's Cage! Where are you from and what are your interests?
     
  6. Faraday's Cage

    Faraday's Cage

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    Mar 21, 2019
    I grew up in New York, but living in California now that I've graduated from university (computer science). I'm interested in pretty much all things science-related, but I am recently getting back into electronics and 3D printing. As my post earlier mentioned, I used to (mostly around 2007-2010 I think?) frequent the electronics forum at dutchforce.com, which is now down. If you're more curious about my interests, I have a twitter that I think is fairly reflective of my interests.
     
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