In order to satisfy my bloodlust for the Inspire 1, at least temporarily, I've decided to try and maximize the performance of my IRIS+ w/ Tarot 2D and GoPro, especially for video and photo. I have the following upgrades to make and thought it might be useful to post the process and results here as I go.
- GPS/Compass: install a Ublox GPS + Compass Module with mast as a new primary GPS, retaining the existing internal GPS as a secondary source. I'll have a very similar mount to this. My current model is the + upgrade kit on the original IRIS, with the original covers and configuration.
- GoPro lens filters: I'll test all three of the filters here. I have high hopes for these, although I might need to make some adjustments for the filters to fit all the way on the lens despite the blue Tarot bracket. I'm especially excited to see if I can get some decent nighttime shots with my basic GoPro.
- FPV: The hit-or-miss aspect of flying photos and video without FPV and trying to frame shots at a distance with little depth perception is a fun and useful learning experience, but at this point I'd like more reliable outcomes. There's a very reasonable looking kit from Helipal here. With a splitter I'll power it off the gimbal power source exactly like the LiveView system does.
- Gimbal Dampers: I've read that the Tarot rubber dampers on the 2D gimbal are not ideal, so I'll try a couple stiffer replacements, especially with the added filter weight and FPV cables.
The idea is to get the low-hanging fruit first, so I'm sticking with my existing GoPro Hero 3 White and the Tarot 2D for now to see what I can get out of it before I consider a camera upgrade or 3D gimbal. If you have any experience with these modifications, I'd love to hear about your results.
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Well, there's another half an hour spent on what exactly a dipole antenna is. I think that's what the IRIS setup is attempting (2 equal length wires, presumably cut to the right length to resonate efficiently, positioned apart at greater than a 90 deg angle). If so, I bet I could get much better performance with a simple reposition.
I also wonder if the failsafe thresholds for FS_THR_VALUE or RSSI or whatever triggers the warnings are set too conservatively by default. Maybe I've got another 400m, but the beeps send me hurrying home.
The two styles for a dipole commonly seen are sleeved dipoles like the ones I linked in for Rob above and regular dipoles that are shaped like a T. If you rip the rubber bit off your transmitter antenna you'll find a sleeved dipole. These are commonly half-wave dipoles (total length, quarter per element), as short dipoles are inefficient.
The RSSI beeps from the transmitter don't actually have anything to do with the pixhawk. They are built into the FrSky module. 1, 2 and 3 beeps indicate something along the lines of 45, 43 and 41 percent RSSI respectively. I think the receiver quits somewhere in the upper 30s, at which point the Pixhawk will go into falesafe. That's assuming you don't have the RSSI hooked up between the pixhawk and receiver.
Thank you for the explanation, Muhammad. It sounds like a little empirical experimentation is in order.
Thanks, that's interesting. The beeps have been a bit of a mystery, especially the thresholds you mention. So I have to consider which will fail first in a range test, the Pixhawk's FS_THR_VALUE or the FrSky RSSI...
I'm pretty pumped about my new dipole smarts, it looks like resonance increases and impedance decreases are ideal at slightly less than half-wavelength for total antenna length (both pieces total, or quarter-wave monopoles as you say above), so hopefully I'll find something close to that (29mm-31mm) under the hood. I understand your rationale a little better now for how the antenna is aligned as well, a horizontal V or T shape taped under the shell is not going to be ideal since I'd be "looking up the wire's butt" a lot on the Z-axis when flying at low altitudes.
Rob,
Testing things out on the ground is a great way to see how antennas behave (roughly). I tape a Rx and antennas to a piece of cardboard in different orientations and tape that to my mailbox. With my transmitter in range-test mode, I walk down my street and take note of the distances I hit 45% RSSI with some rocks. Very roughly qualitative, but interesting nonetheless.
Thanks. I think this is the one you are referring to?
I understand about the radiation pattern. No free lunch there. I was hoping someone had some thoughts on better placement of the internal antennae or something. As you can see in the picture above, the two wires just sort of run together for a bit and then the last few inches split off. Just doesn't seem that well thought out.
I almost exclusively use these on receivers: http://www.alofthobbies.com/25cm-receiver-antenna.html
The phantoms have both dipoles pointing downward in adjacent legs. The idea is that if one antenna is blocked by the camera it will switch to the other. Being on adjacent legs, there's always at least one in good view of the Tx.
On my quad I have one pointing vertically on top and one pointing backwards on the bottom. The idea behind having one horizontally polarized on the bottom is that It would switch to it if I flew over myself where one of the vertical antenna's null-points exist, but it rarely switches to it.
Some folks place them in a v configuration on top. This works well too, but I feel like this is more beneficial on a fixed wing since our copters are flying level most of the time.
Also, your control should in general out-perform your video in terms of distance, even with cp on the video. Directional video antennas can invalidate this.
What do you mean by the RC antennas and 915? The stock rc transmitter antenna is 2.4 and does pull down some telemetry data.
The other antenna on a stock IRIS is 915 (N. America) and that's your telemetry antenna. 915 has great distance normally. Are you using Mission Planner or a Droid tablet?
As far as FPV antennas go, yeah, everyone seems to be going to the CP antennas. This site allows you to play around with different setups to see what may work best for you. www.maxmyrange.com Plug in your equipment and see what distances it comes up with. Note that these are suggested distances in optimal conditions but you can really see what a difference antennas make.
-Mike
I don't know what to think, because my stock 915 telemetry has terrible distance, using Mission Planner or Tower/Android device. And then I've read that 100m is about what I should expect of the stock telemetry, which is about what I'm getting.
You're right, I was thinking of an upgrade to the 2.4 RC antennae depending on how my range tests go. People talk about 600m, 800m, even 1200m radio range with stock IRIS equipment, so I'm chasing down why I'm not getting anywhere close to that. I honestly haven't really evaluated the stock RC transmitter quality, all I know is that it's not cutting it at the moment. Or something's off. I definitely need to do more testing before I just go buying random stuff, as it seems like 90% of issues like this so far have been much more to do with my ignorance than the hardware.
Cool site, thanks!
If I needed another FPV transmitter I'd probably try this. On the pricey side, but I'll be pushing the limits of the IRIS+ payload with a camera, gimbal, GPS and mast, AND a 55g FPV transmitter. This one comes in at just 20g with about twice the range, helped a lot by the stock circular antenna, and I suspect small enough to fit inside the shell.
Yeah, the video transmitter I got is huge and heavy, larger than most of the examples I've seen. I might have to mount it to the underside of the battery door.
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