Signal Loss and Time to RTH

[Bob Johnston]

The manual states that "after signal loss, rth is initiated after 3 seconds using the controller, and 20 seconds on wifi" I am using the controller but find it takes around 20 seconds for rth initiation after signal loss. The second part "on wifi" is confusing, as I thought all control was on wifi??? Anyone have some illumination on this.
Thanks

 

[Haggi]

3 sec with RC..
20 sec without RC...just by phone or tablet

I could be wrong

 

[msinger]

The second part "on wifi" is confusing, as I thought all control was on wifi?

That part is referring to flying with only a mobile device (no remote controller).

 

[Bob Johnston]

3 sec with RC..
20 sec without RC...just by phone or tablet

I could be wrong

And that's my question or issue, with controller I'm getting rth only after 20 seconds not 3 as manual states.

 

[Bob Johnston]

That part is referring to flying with only a mobile device (no remote controller).

Ok, thanks.

 

[msinger]

And that's my question or issue, with controller I'm getting rth only after 20 seconds not 3 as manual states.

Are you sure the remote controller is actually disconnected? Is it possible the Spark is ascending to the RTH altitude when it seems it's not initiating RTH after 3 seconds?

 

[Bob Johnston]

Thanks msinger. This is the Airdata inpuut similar to several other flights loosing signal and RTH.
"M 02m 17s 112.2 ft 2,581 ft Mode Mode changed to GPS_Atti
N 02m 19s 110.2 ft 2,605 ft Mode Mode changed to Sport
02m 20s 110.6 ft 2,638 ft

78% Battery at maximum distance
O 02m 47s 165.0 ft 2,498 ft Data Loss Downlink data connection lost for 26.7 seconds
P 02m 47s 165.0 ft 2,498 ft Mode Mode changed to Go_Home
Q 02m 55s 165.0 ft 2,224 ft Mode Mode changed to WiFi_Reconnect
R 02m 56s 164.7 ft 2,188 ft Mode Mode changed to Go_Home
S 03m 13s 164.7 ft 1,630 ft Mode Mode changed to WiFi_Reconnect
T 03m 14s 165.0 ft 1,614 ft Mode Mode changed to Go_Home
03m 27s 165.0 ft 1,183 ft"
Interesting that line O not reported until distance actually less than line P. Maybe lag in event data report vs event?

 

[Bob Johnston]

DJI Flight Log Viewer - PhantomHelp.com
After review of the csv and phantom help it appears that it took around 26 seconds to go from 110 to 165 ft altitude for rth at which time it reacquired the downlink. My questsion now is when does the transmitter give the RTH notification;Before or after ascent to RTH altitude.With no downlink, can the controller report initiation of of RTH or have to wait until down link is restored?
I realize I'm nitpicking this, but its the way I build understanding and confidence in the aircraft.

 

[msinger]

The "Downlink Restored (after 0m 26.7s)" message means the Spark was not sending data back to the remote controller for 26.7 seconds. That doesn't necessarily mean the uplink (remote controller connection) dropped at the same time. RTH is initiated 3 seconds after the uplink drops.

If we assume the downlink and uplink dropped at the same time, your log tells us the following:

• RTH was initiated before the downlink reconnected
• There was a maximum time of 23 seconds when they Spark could have been returning home
• The Spark ascended 54 feet and traveled 139 feet
  
  

when does the transmitter give the RTH notification

It doesn't. The Spark initiates RTH on it's own after the uplink drops.

Before or after ascent to RTH altitude

When RTH is initiated, the Spark will ascend to the RTH altitude before it starts flying back to the home point. The ascent and flying back are both part of the RTH process.

With no downlink, can the controller report initiation of of RTH

No. You won't know the Spark is returning home until the downlink reconnects.

 

[Bob Johnston]

Ok, thanks. I have a much clearer picture of the RTH process for the Spark. With Standard, you usually had control of ac even if video was lost, so RTH was initiated manually, unless of course you were flying blind with no telemetry and video. Different units.I really like the Spark size,and distance is pretty similar to Standard.
One question I still am not clear on, when using 5.8ghz, is video on 2.4, and vice versa for 2.4,or are all streams(control,video,telemetry) on either chosen 5.8 or 2.4?

 

[msinger]

With Standard, you usually had control of ac even if video was lost, so RTH was initiated manually, unless of course you were flying blind with no telemetry and video.

This is how the Spark (and all other DJI drones) works too. RTH is not initiated until the uplink drops.

when using 5.8ghz, is video on 2.4, and vice versa for 2.4,or are all streams(control,video,telemetry) on either chosen 5.8 or 2.4?

All are 2.4 or 5.8.

 

[cozzykim]

All are 2.4 or 5.8.

Wow! That's interesting, I'd assumed that the Spark/RC/Phone combination could use a mixture of bands as required.

Not questioning the accuracy of your statement at all, but, where did you find that info?

Thanks.

 

[msinger]

Not questioning the accuracy of your statement at all, but, where did you find that info?

That's my understanding of how it works. Unless you manually set the video frequency in DJI GO, the Spark will auto choose the best available frequency. The remote controller also auto sets the frequency. Could both determine a different frequency is best? Maybe. I don't think it's likely though.

 

[cozzykim]

That's my understanding of how it works. Unless you manually set the video frequency in DJI GO, the Spark will auto choose the best available frequency. The remote controller also auto sets the frequency. Could both determine a different frequency is best? Maybe. I don't think it's likely though.

I'd assumed that the system would use different bands for each connection, to reduce the chances of crosstalk type interference.

I would have thought that also choosing one band/channel for RC-AC and the other for RC-Phone would mean that both then are likely to find it less crowded given the limited number of channels, if you see what I mean?