Hi there ...All pictures I've seen of different hexa,cuad,tri, y6 ... etc copters got the different antennas pointing up. But then we are usually BELOW the copter, when it flies.I got three antennas out of my 3DRobotics Y6: Video, data and flight receiver. I carefully point them down, I placed the different transmitters and receivers, pressed between the space in the first sandwich leve (where the three legs are attached into the Y6 body.I even am afraid that by pointing them UP we are probably disturbing the GPS and or magnetometer chips ?Is there any rationale on this (or lack of) ?Regards,Enrique
You need to be a member of diydrones to add comments!
I'm going to reply mostly out of theoretical knowledge with a limited amount of experience mounting antennas on my airframes. Would love to hear someone else with more experience on actually integrating all this stuff into a multirotor chime in....
Generally speaking I'd expect mounting the control, telemetry and video antennas below the center frame of a multirotor to be a bit better than mounting antennas above in terms of interference with the GPS for two reasons. First, most rubber-duck antennas like most video TX's come with, or the stock 3DR telemetry radios will output a fairly toroidal pattern - where most of the RF energy is leaving the antenna perpendicular to the direction the antenna points. Think of a donut coming out from the sides of the antenna, and basically no energy coming out of the two ends: http://www.antenna-theory.com/basics/pattern.JPG
So, putting an antenna next to each other would put them in the maximum power portion of the pattern - where as putting the antenna below the GPS chip puts the GPS in a less powerful part of the radiation pattern.
Further, the inverse square law means that as you double the distance between the TX and the RX, you're quartering the power: http://en.wikipedia.org/wiki/Inverse-square_law - So, mounting a few inches further away from the GPS on the bottom of the craft (in the lower power part of the donut pattern) should theoretically reduce the RF energy at the GPS position by quite a bit.
Now since for the most part the frequencies that our control / telemetry / video links use are away from the GPS frequencies this shouldn't be too much issue anyway - but in the case of spurious emissions on unwanted frequencies, or a frequency harmonic, this mounting should reduce the chances of swamping the GPS chip in noise.
I haven't experimentally confirmed this mounting pattern improves TX / RX range or interference with the GPS, but as an anecdote I've mounted my antennas this way and seen many others do this as well - and it seems to work well for me.
Understood ... So, the way I am placing the antennas, all pointing down, is OK :) It was just common sense, but then , most Y6 photographs depict antennas going up ...
Replies
Hey Enrique,
I'm going to reply mostly out of theoretical knowledge with a limited amount of experience mounting antennas on my airframes. Would love to hear someone else with more experience on actually integrating all this stuff into a multirotor chime in....
Generally speaking I'd expect mounting the control, telemetry and video antennas below the center frame of a multirotor to be a bit better than mounting antennas above in terms of interference with the GPS for two reasons. First, most rubber-duck antennas like most video TX's come with, or the stock 3DR telemetry radios will output a fairly toroidal pattern - where most of the RF energy is leaving the antenna perpendicular to the direction the antenna points. Think of a donut coming out from the sides of the antenna, and basically no energy coming out of the two ends: http://www.antenna-theory.com/basics/pattern.JPG
So, putting an antenna next to each other would put them in the maximum power portion of the pattern - where as putting the antenna below the GPS chip puts the GPS in a less powerful part of the radiation pattern.
Further, the inverse square law means that as you double the distance between the TX and the RX, you're quartering the power: http://en.wikipedia.org/wiki/Inverse-square_law - So, mounting a few inches further away from the GPS on the bottom of the craft (in the lower power part of the donut pattern) should theoretically reduce the RF energy at the GPS position by quite a bit.
Now since for the most part the frequencies that our control / telemetry / video links use are away from the GPS frequencies this shouldn't be too much issue anyway - but in the case of spurious emissions on unwanted frequencies, or a frequency harmonic, this mounting should reduce the chances of swamping the GPS chip in noise.
I haven't experimentally confirmed this mounting pattern improves TX / RX range or interference with the GPS, but as an anecdote I've mounted my antennas this way and seen many others do this as well - and it seems to work well for me.
- Ian
Ian,
Understood ... So, the way I am placing the antennas, all pointing down, is OK :) It was just common sense, but then , most Y6 photographs depict antennas going up ...
Regards,
Enrique