Lost communication AC M2Z with RC

[CarlosCN]

I lost contact with AC (M2Z) after ca. 500 m at 118 m altitude. Signal was lost after passing buildings on the route. Buildings are ca. 50 m height and 200 m away from my position.

I have problably underestimated the influence of obstructions on the connection.
I was flighing in a “secondary” flight restriction zone in China (max. altitude 120 m). Do those FRZ have any influence on the signal quality?

The RTH saved my investment. Fortunately, I set the return hight at 100 m.

Comments will be welcome.
Thanks

 

[Goof]

The zones themselves won't affect signal, but they will typically coincide with increased urban activity and signal pollution from other sources.

Beware of trusting the RTH's obstacle avoidance to safely ascend over buildings. Often buildings have thin antennae on the roof which the AC may struggle to detect. The AC can successfully avoid the building itself only to crash into something mounted on top. Not much choice if it's a lost signal RTH or critical battery, but at least the latter can be avoided through proper flight planning. Former can be mitigated at least by ensuring LoS to the AC, and also ensuring the AC flight path never places its RTH course through a building.

 

[CarlosCN]

Thanks Goof for your comments.

Can you please provide more details about the signal being lost at such short distance (500m) due to obstructions?
Despite the building around me, I was not expecting such strong interference.
Does it mean that I can only fly from the top of a montain?

 

[gnirtS]

Remember at microwave frequencies even some relatively low density tree branches can eat a signal up entirely. Range is good but you really do need *unobstructed* complete line of sight regarding signal path.

 

[CarlosCN]

Remember at microwave frequencies even some relatively low density tree branches can eat a signal up entirely. Range is good but you really do need *unobstructed* complete line of sight regarding signal path.

Ok. Thanks for your comment.
According to your experience, what is the reliability of RTH in case of signal loss?

 

[gnirtS]

No idea. I've lost signal twice in 400 flights, both times it came back the second the drone started to climb.

 

[Goof]

I can't speak for the mavic yet since mine is shipping, but I've had dozens of lost signal events on the P4 and it's come back each and every time. Usually I've cancelled the RTH once I regain full control and good RC signal and then continue flying. Where I am under CE regulations, our transmit power is less than the FCC limit, so it's fairly easy for signal to drop out.

Regarding signal loss around buildings, it could be simply a combination of a congested 2.4/5.8GHz space causing the radios to struggle to talk, combined with the fact that it only takes a decent sized bush to obstruct 5.8GHz, let alone a whole building... The signal will refract around a building to an extent, but you will likely suffer significant signal degradation. This is merely speculation on my part though, I fly well outside towns where there is 0 interference on 2.4GHz; my signal losses tend to be due to distance and/or dropping below the treeline.

If there's any RC radio enthusiasts around they can probably offer a much better explanation on the specifics than I can.

 

[CarlosCN]

No idea. I've lost signal twice in 400 flights, both times it came back the second the drone started to climb.

Ok thanks GnirtS!
Cheers

 

[CarlosCN]

I can't speak for the mavic yet since mine is shipping, but I've had dozens of lost signal events on the P4 and it's come back each and every time. Usually I've cancelled the RTH once I regain full control and good RC signal and then continue flying. Where I am under CE regulations, our transmit power is less than the FCC limit, so it's fairly easy for signal to drop out.

Regarding signal loss around buildings, it could be simply a combination of a congested 2.4/5.8GHz space causing the radios to struggle to talk, combined with the fact that it only takes a decent sized bush to obstruct 5.8GHz, let alone a whole building... The signal will refract around a building to an extent, but you will likely suffer significant signal degradation. This is merely speculation on my part though, I fly well outside towns where there is 0 interference on 2.4GHz; my signal losses tend to be due to distance and/or dropping below the treeline.

If there's any RC radio enthusiasts around they can probably offer a much better explanation on the specifics than I can.

Ok Thank you.
I will refrain to flight near buildings.
For me it’s stil too scary losing signal.