07-06-2023, 03:59 PM
Another incident!
My slick is a 90cm span 3d plane with a elrs matek R24P rx; it has a 2S lipo that I connect to the vbat plug signal pin (in row7 of pwm pins) to monitor lipo voltage. In the following plots from monitoring a flight yesterday a burst of throttle led to a sharp decline in the rx signal-to-noise ratio (RSNR). As pilot I was not aware of any change in signal link quality, although I got the warning about the jump in tx power to 25 mw.
Up to 129.5 sec into the flight RSNR was 10 or 11, and TPWR (tx power) was 10 mw. At 130s RSNR fell to 6 and TPWR was 10. At 130.5 s RSNR fell to 3 and TPWR increased to 25. TPWR remained at 25mw until 137 sec into the flight, when it returned to 10mw.
Throttle setting has a range of -1000 to + 649 in the flight log. I divided values by 100, providing in the plot a throttle range -10 to the flight maximum throttle of 6.49 which occurred at 128.5 sec.
Lipo v. dropped from 7.1v at 127 s to 6.8 at 128 s; this is normally plenty of power for the esc.
It is clear from the plots that an burst of throttle at around 128 s into the flight triggered the fall in RSNR and the jump in tx power (TPWR).
What does this mean? A fall in RSNR caused a jump in power, as expected, however a RSNR that fell to 3db means the signal is still 3 times stronger than the noise, and it seemed this was enough to avoid a loss of RSSI (rx signal strength indicator) and RQly/VFR (rx valid frame rate). It is unclear whether the incident was caused by a loss of signal-to-noise due to interference, or a drop in rx voltage, or something else.
What I need to do is to monitor the rx voltage. Unfortunately I am using the vbat on the r24P for the lipo voltage, and I have now decided to modify the slick and other planes to allow rx voltage monitoring instead. I use the lipo voltage for deciding when to land, and I am reluctant to give it up. However I now think rx voltage monitoring has priority.
My slick is a 90cm span 3d plane with a elrs matek R24P rx; it has a 2S lipo that I connect to the vbat plug signal pin (in row7 of pwm pins) to monitor lipo voltage. In the following plots from monitoring a flight yesterday a burst of throttle led to a sharp decline in the rx signal-to-noise ratio (RSNR). As pilot I was not aware of any change in signal link quality, although I got the warning about the jump in tx power to 25 mw.
Up to 129.5 sec into the flight RSNR was 10 or 11, and TPWR (tx power) was 10 mw. At 130s RSNR fell to 6 and TPWR was 10. At 130.5 s RSNR fell to 3 and TPWR increased to 25. TPWR remained at 25mw until 137 sec into the flight, when it returned to 10mw.
Throttle setting has a range of -1000 to + 649 in the flight log. I divided values by 100, providing in the plot a throttle range -10 to the flight maximum throttle of 6.49 which occurred at 128.5 sec.
Lipo v. dropped from 7.1v at 127 s to 6.8 at 128 s; this is normally plenty of power for the esc.
It is clear from the plots that an burst of throttle at around 128 s into the flight triggered the fall in RSNR and the jump in tx power (TPWR).
What does this mean? A fall in RSNR caused a jump in power, as expected, however a RSNR that fell to 3db means the signal is still 3 times stronger than the noise, and it seemed this was enough to avoid a loss of RSSI (rx signal strength indicator) and RQly/VFR (rx valid frame rate). It is unclear whether the incident was caused by a loss of signal-to-noise due to interference, or a drop in rx voltage, or something else.
What I need to do is to monitor the rx voltage. Unfortunately I am using the vbat on the r24P for the lipo voltage, and I have now decided to modify the slick and other planes to allow rx voltage monitoring instead. I use the lipo voltage for deciding when to land, and I am reluctant to give it up. However I now think rx voltage monitoring has priority.