As mentioned earlier one of the major contributing factors at our club is Drones, without generalizing many of the drone guys are a decent bunch, very sensible and have some really nice equipment (DJI, Yuneec etc.) which are CE and FCC approved I might ad. However, we also have some other gadgets (home built FPV’s to mention a few), which are NOT regulated and/or approved, and are different to the common DRL FPV’s. Hover one of these close to your TX and your telemetry warning goes crazy (Spectrum DX18).
Anyway, up until about 18 months ago there were NO signal issues to speak of (and it had been like this since we migrated from the older FM days with the Peg and Board System), but lately there has been approximately a dozen signal related incidents with about 60% of those resulting in a crash.
With all the data that we collected the most venerable system has been DSM2. This system would go into failsafe – with the most common settings being HOLD (and a few other settings such as gear down, throttle to idle, etc. depending on the users preferences), and in ALL these cases the RX never recovered, they simply maintained their last controlled input until impact. On other occasions with DSMX, FHSS and FASST the models in question also went into HOLD, but recovered after several seconds and a safe landing was made, albeit with a shaky pilot at the helm (only one FHSS crash to date).
I must also highlight that all the models in question; the installations were scrutinized by myself (and other experienced modelers), with single RX setups having dual battery redundancy, and Two RX setups using Power Management Units. One of the most common errors with Two RX setups is the guys would mirror both RX antenna’s so we would make them change this so that all four antenna represent the four axis. The point being that poor installations and setups were unlikely to be the root cause.
So we asked ourselves what has happened, what has changed recently, and several factors seemed very plausible (including new military activity), so we started to collect data, which of course can be very subjective. To know for sure you would have to fly the same model, the same routine, whilst changing manufacturing RF equipment, etc. and this would be impossible, so I decided to do the following and use Gliders, three 6-meter gliders.
WHY, because the're big, they fly high and far, and there would be no contributing external influences in the cockpit/cabin (such as ECU, Fuel Pump, Smoke pump, Ignition, and so on), just two receivers, a power distribution unit, and some servos. All gliders were 6-meter wingspan; all had the same power distribution unit, RX’s and antennas mounted in very similar locations, but all had different manufacture Radio Equipment. Not perfect I know but at least you can collect and record data from three models that have all flown at the same time and in similar parts of the sky.
The results from my 6-meter Ventus were recorded via my JETI telemetry and PowerBox Competition SRS with Zero Lost Frames and Zero Holds. Typically the TX Q-line data will remain almost straight at 100% but on this day there was certainly some periodic RF Noise. Under the same conditions the gliders with other systems recorded almost 100 Lost Frames and several Holds.
To conclude both Weatronic (BAT 60), and JETI are handling “our sometimes erratic”, high noise and hostile RF environment with excellent results.
Additional Information:
FCC Part 15 limits RC 2.4GHz to 247mW and CE conformity limits it to 100mW (perhaps some of you guys can confirm and elaborate on this). Over here some home made units will transmit at extremely high power outputs.
JETI telemetry has a really nice feature where you can download/record your A1/A2 and Q signals. A1 and A2 is the RX signal antenna strength (that the TX receives), and Q is the overall performance of how well the RX understands.
Tassos: Futaba FASST shifts frequency hundreds of times per second, so there are no signal conflicts or interruptions – and no need for frequency pin. As far as the PowerBox protocol works it registers the Two RX’s and uses both RX’s at the same time. JETI does it differently as each RX is bidirectional so Two RX’s is like having four. The P/Box will use the strongest RX (bidirectional signal), and switch automatically should the other one be stronger due to airplane orientation.
Here are some interesting links:
http://www.thenational.ae/uae/201609...drone-activity
http://www.thenational.ae/uae/uae-av...one-disruption
https://www.rc-thoughts.com/
http://www.futabarc.com/faq/faq-fasst.html
Last edited by darryltarr; 04-06-2017 at 09:12 AM.
Reason: typo