What do the two signal bar graphs really measure?

[joeruby]

What does the RC app up-link and the down-link bar indicators really measure?

I am using the Litchi app with my P3P, but the same questions goes for the DJI-Go app.

That is:
1) Does the up-link indicator measure the RC transmitter RF output power sent to the AC? Does this measurement depend on the AC receiving the signal? In other words will this measurement be the same if the AC is 10 feet away, or 10 miles away, from the RC.

2) Does the down-link indicator measure the AC transmitted power as received by the RC receiver?

3) What information does the up-link signal carry from the RC to the AC?

4) What information does the down-link signal carry from the AC to the RC?

Thank you for your help answering these questions for me.
Joe
KC7GHT

 

[With The Birds]

What does the RC app up-link and the down-link bar indicators really measure?

I am using the Litchi app with my P3P, but the same questions goes for the DJI-Go app.

That is:
1) Does the up-link indicator measure the RC transmitter RF output power sent to the AC? Does this measurement depend on the AC receiving the signal? In other words will this measurement be the same if the AC is 10 feet away, or 10 miles away, from the RC.

NO.. varies with dirtenernce and signal quality

2) Does the down-link indicator measure the AC transmitted power as received by the RC receiver?

Yes- signal quality

3) What information does the up-link signal carry from the RC to the AC?

Control signals

4) What information does the down-link signal carry from the AC to the RC?

Video and telemetry

Thank you for your help answering these questions for me.
Joe

It's not clear what signal quality means, DJI has seemingly not provided detail. It may not be pure RF strength (data quality may have a bearing, ie packet errors)

 

[John Decker]

dirtenernce?
Is your auto - correct a pain in the ar$e too or is this a technical word I've not come across!

 

[N017RW]

RSSI by definition is received strength thus the 'R'.
Typically the Tx power is constant though there are exceptions (such as your cellphone) so an indicator of it is of little use.
The units or value of each 'bar' are often arbitrary so it is usually meant to be relative from min-to-max based on Rx signal requirement and not some means of being secretive or otherwise proprietary.
This can also be a combination/calculation of RF power, Bit Error Rate, SNR, etc. however for simplicity and relevance to an r/c pilot- it is likely just RSSI.

 

[joeruby]

This answer below from Eran at airdata.com provides me some insight into the real answers to my questions above. Thanks Eran.

Here is what Eran told me:
~~~~~~~~~~~~~~~~~~~~~~~~
"Generally, the up-link signal bar refers to how strong is the signal the aircraft can read from the remote, and the down-link bar measures how strong the signal the remote can read from the aircraft. In other words, the down-link bar will indicate how well the video feed is, and the up-link bar will indicate how well you can control the aircraft with the remote.

I hope this helps,
Eran"
~~~~~~~~~~~~~~~~~~~~~~~~

For the up-link signal - this implies that the AC must respond back to the RC, with telemetry, as to how strong the AC received the up-link signal from the RC. Thus there is two way communication on the up-link signal, but I don't think there is two way communication on the down-link signal.

Does anyone have a block diagram of the information flow on both links for the DJI P3P?

Thanks,
Joe