Replies

    • Pavel > Ben Norris October 7, 2015 at 5:35am

      The advice is generally especially usable for somebody who is getting only small control range or not reliable remote control with with open LRS remote control and some other UHF frequency band remote control systems. Also for sophisticated users which prefer improve things to maximum. The advice generally probably is not for user which likes plug and play working systems and which system is working in their usable remote control distance they usually fly.

      Regarding if it is nonsense or not that is very questionable. Please read comments from Alasdair and R. D. Starwalt to find out their opinion also.

      PS: I will probably try to do demonstrate some test which should hopefully prove if APM is able to cut remote control in some situations under some specific conditions or not when I will get a time. The practical answer should be yes or not.

      Regards

    • Ben Norris > Pavel October 7, 2015 at 6:59am

      No. If you come up with a crazy theory it is up to you to find some evidence BEFORE you claim that it is actually happening.

      Or else it is a question and you can't argue with other people's experience that it does not occur.

    • Moderator
      RM Aviation > Ben Norris October 9, 2015 at 6:05am
      Hi Ben, firstly may I apologise for replying out of sequence to your latest post- for some reason I cannot reply under it. There seems to be some confusion in to exactly what we are all discussing which is leading to problems. Pavel has not to my knowledge ever claimed that the apm is causing issues to the majority, this is only a discussion over one particular scenario. If this is understood and the basic electronic and rf theory is applied we can see that the idea has scientific basis and merits discussion, more so we can also see that he is actually testing it in the only real way possible.
      His distinct point of contention is that when using a UHF signal at its weakest strength, it looses performance due to background noise from other electrical components that includes the apm. I can see from your post that you accept that the apm generates noise as I have previously explained (at a very low level and without much distance). If we apply a suitable analogy, let's say trying to listen to a conversation far away that is approaching the limit of your hearing range. It does not take much noise close to you to render that conversation inaudible. Therefore, any noise that is generated will raise the noise floor and potentially affect the signal capability. Now as for how to test this supposition, it is standard practice to start looking for signals on particular frequencies but this is only part of it. Measuring the noise floor is almost impossible, as Alasdair had alluded- in order to measure you have to set a starting point. This is not as easy as you may think. Then you have to factor in as I have already pointed out, that the amount and type of noise generated is partly controlled by the processing and workload of the systems which changes all the time whilst in flight. Don't even begin to take into account sunspot activity etc.! Therefore one of the best ways to investigate is to shield various components and see if anything improves......
      When you take all this into account you begin to see that Pavel is far from any of those things you called him. We are not discussing particular signals being generated by the apm on the UHF range, this is all about the general noise floor when operating at the limits and if shielding may help.
    • Developer
      Bill Bonney > Ben Norris October 7, 2015 at 9:00pm

      Pavel proposition is not crazy. There will be some interference, it's just too small to be an issue in most cases. The solution, is a partial solution, not perfect. The testing is ad-hoc, but I know plenty of Hams that use another radio to scan for interference, light bulbs as current limiters etc.. It's part of the 'hobby' side of figure stuff out.

      The problem may be only be apparent with interference generating components close together, distance is the best in all cases as the interference drops of so quickly with weak signals.

      The only problem with this thread is the commentary that moves from 'interesting' type discussion and critique, to playground bullying. That doesn't usually happen that much on this site.

      As for tin foil hats, it you know anything about RF, you need a tin foil suit to be protected, maybe ;-p

    • Moderator
      RM Aviation > Ben Norris October 7, 2015 at 2:46pm
      I'm sorry to say Ben but RF noise due to clock oscillators in digital equipment is basic electronic theory. There are really two general kinds of digital interference: that due to the "clock" oscillators in computers, peripherals and other digital devices, and that which is caused by the processing in a digital device. They are just another form of direct interference that is caused by leakage of radio signals at the digital clock frequency or some multiple and interference caused by the operation of the internal processor (or digital signal processor) in the device. The interference is not necessarily at a multiple of the clock frequency; instead it can be related to the rate at which instructions are being processed. The level and character of the interference can vary greatly with the type and amount of processing occurring, and the interference can disappear entirely if the digital device is not actively processing. Digital interference is usually relatively easy to identify. The signals involved are not strong and rarely affect systems at distances greater than about 6 feet.
      Now the question as to wether this is applicable to us is uav design is a different matter. Suitable placement of components goes a long way in tackling the problem but shielding is also a valid point for discussion. For a more technical explanation please see Alasdairs post in this thread.
    • Ben Norris > RM Aviation October 8, 2015 at 5:07am

      No, the fact is that some electronics give off RF interference but there is no sign that the APM gives off any significant amount.

      What makes Pavel crazy is that he has done no test to identify the APM as a source whatsoever and yet still claims it is despite wide experience and actual tests with the proper equipment show it is not one. He states other components which are known offenders such as the mobius/runcam, then falsely assumes that the flight controller must be too.

      To ask the question is not stupid. To dispute people who have tested it and found it not to be the case when he has no evidence at all is very foolish.

  • naish October 5, 2015 at 6:46am

    Hi Pavel,

    I had a look at the APM mini schematic, and is essentially the same as the APM. There is notting in therms of circuitry or devices that can radiate enough power on the UHF frequency to affect your RC receiver. I'm unsure about the power module you use. 

    I will also like to add you some notes:

    Shielding with aluminium foil won't help for 2 reasons, first because your problem is not the APM and second because you need to do a proper ground shielding to become effective. 

    Wrapping the APM in aluminium foil won't affect any of the sensor onboard, and there is no need of perform again a magnetometer calibration, since alloy is not a ferromagnetic material. 

    Open LRS it's not a true spectrum analyser that will help you to troubleshoot this kind of issues, to do so you need a "true" spectrum analyser that is out of reach for most hobbyist.

    I will suggest you to review your system and place some attention on power and antennas/transmitter placement. Issues like ground loops or RFI transmitter ( non radiated ) form other devices travelling on you power wires can kill your range. 

    Also just a personal suggestion. When you post on a forum like this, if you make a statement be prepared on demonstrate what you are claiming because people will ask for. Particularly if what you are claiming requires serious RF knowledge to be proven, and if you do have such skills you won't be here asking a basic RF shielding question. It's a scientific forum not a gossip one. 

    • Pavel > naish October 5, 2015 at 10:06am

      Hi naish88,

      Thanks for reply. I am glad that discussion here starts to return to constructive level. The power module used is this:

      http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=...

      As measured with open LRS spectrum analyzer, this power module also produces UHF noise. So I wrapped it to aluminum foil already to minimize it.

      Ground Faraday Cage aluminum foil shield is not necessary. See this practical experiment example video, that it simply works without ground, please.

      Yes, by definition of Faraday Cage, the magnetic field for compass should still work. (Today and yesterday flight proved it.)

      https://en.wikipedia.org/wiki/Faraday_cage

      "Faraday cages cannot block static or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside). "

      Thanks for confirmirming this.

      Open LRS UHF band spectrum analyzer is a tool which is more than enough to find differences in spectrum. That it is why you can measure and let draw graph of normal UHF spectrum signal with no electronics powered and measure and draw to the same graph UHF spectrum when some electronics component is powered. You can see detailed difference. Would recommend to try and play with open LRS.

      I momentarily do not have any observed range issue, since I have more or less all measured problematic electronics components wrapped with aluminum foil. It simply solved it. Thanks for tips and suggestions though.

      (There was one issue with not wanted grounded aluminum foil of RunCam HD camera, it looks like via ground wire it propagated to other components. It was solved by isolating the aluminum foil to not to touch the USB connector ground. Then the noise stopped to be propagated.)

      I have practical experience and some knowledge in area, which I can use to prove the fact that even if electronics component was not designed to generate electromagnetic noise, it simply produces it. First it can be measured with spectrum analyzer. And second it can be proved with practical experiments the way that we can try, if placement of such electronic component near remote control receiver will not cause loose of control or interference. In the case if transmitted remote control signal is small, which is when our UAV device is far away it is very important. We can simulate such behavior with attenuator on RC transmitter connected prior to transmitter antenna and or minimize the transmitter transmitted power and or to walk far away. I did similar experiments as in video above where Mobius HD cut RC control, also with Mobius HD, with RunCam HD camera,video transmitter and it cut the remote control. I have measurements, graph of noise of such components. I can compare noise levels. I can try to do similar experiment with APM to prove it, if it will cut RC control, if I will have a time and without promise.

    • Pedals2Paddles > naish October 5, 2015 at 8:31am

      I tried to explain to him that simply wrapping tin foil around something doesn't make it shielded. That's called an antenna :).  It just changes how the RFI is radiated rather than blocking it.  It might actually make it worse!  The foil would have to be grounded with very few gaps.  This is probably why he reported seeing the RFI move and change rather than go away in some of his attempts to shield the cameras.

    • Pavel > Pedals2Paddles October 5, 2015 at 9:38am

      Pedals2Padles, try to find term Faraday Cage on internet for explanation about why simply wrapping tin foil around problematic electronics component simply works. Without need for grounding. https://en.wikipedia.org/wiki/Faraday_cage "Faraday cages cannot block static or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside).". There is huge discussion over the internet whether Faraday Cage needs to be grounded or not to be effective. But simple experiment as you can watch shows you that it does not need to be grounded to minimize interference. (I even observed opposite behavior when my aluminum foil was grounded by mistake with not wanted connection to USB connector ground. If I isolated it the noise from RunCam HD camera was shielded again. )

      Faraday cage
      A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of con…
This reply was deleted.