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Controller Frequencies

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When I visited our local flying club field yesterday, another member asked me what radio frequency does the inspire use.

Without hesitation I said 2.4 GHz radio and 5.8 GHz video which is what we all come to expect.

He then said something which made me think, Wi fi light bridge works on 2.4 GHz therefore is the radio also 2.4 GHz.

Checking the manual it does state remote controller 5.725~5.825 GHz and 2.400~2.483 GHz

Also confirms radio link between master and slave controller is 5.8 GHz

But what frequency is the video downlink from the inspire.

Any thoughts?
 
2.4 both ways between radio and aircraft, 5.8 between radios on the ground.

Envoyé de mon GT-I9505 en utilisant Tapatalk
 
Checking the manual it does state remote controller 5.725~5.825 GHz and 2.400~2.483 GHz
Also confirms radio link between master and slave controller is 5.8 GHz
But what frequency is the video downlink from the inspire.
The 2.4GHz is used for command and control (C2) between the I1 and RC and for the Lightbridge video downlink with a max power of 100mW. The 5.8GHz is link between the Master and Slave RC for C2 and video with a power of 25mW. This differs from the diagram on the DJI website which shows the video transmitted directly from the I1 to Slave RC.
 
and video with a power of 25mW. This differs from the diagram on the DJI website which shows the video transmitted directly from the I1 to Slave RC.
Where did you get that "info"?
Spectrum analysis shows the diagram is correct, no way video could be sent over the bandwidth used by the 5.8 link.

Envoyé de mon GT-I9505 en utilisant Tapatalk
 
The 2.4GHz is used for command and control (C2) between the I1 and RC and for the Lightbridge video downlink with a max power of 100mW. The 5.8GHz is link between the Master and Slave RC for C2 and video with a power of 25mW. This differs from the diagram on the DJI website which shows the video transmitted directly from the I1 to Slave RC.
Sorry, have to correct you on that one.
The control AND video is transmitted over 2.4ghz using digital transmission for the video along with the standard 'packet' style control link with the usual parity and identity confirmation checks over frequency hopping spread spectrum.
The 5.8ghz link is nothing more than a 'bluetooth style' link between the master and slave to control the camera/gimbal etc.
The 2.4ghz is transmitted at the legal (UK) limit which is 100mw EIRP/20dB. Because the video is 'embedded' digitally it kind of gets round the 25mW limit that would otherwise be applicable for analogue 5.8ghz video transmission.
Hope that clarifies things.
 
Sorry, have to correct you on that one.
The control AND video is transmitted over 2.4ghz using digital transmission for the video along with the standard 'packet' style control link with the usual parity and identity confirmation checks over frequency hopping spread spectrum.
The 5.8ghz link is nothing more than a 'bluetooth style' link between the master and slave to control the camera/gimbal etc.

Let me ask for clarification on one further point. The actual video is received direct from the bird to the slave (or multiple slaves), only the gimbal and camera control, is relayed through the master, right? (that is what I thought anyway)
 
Yep. BUT synchronisation is needed between the controllers for slaves to be able to pick up the video signal. I.e. a slave that is out of 5.8GHz range of the master will not display video even if it could technically pick up the aircraft's video signal.
 
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Yep. BUT synchronisation is needed between the controllers for slaves to be able to pick up the video signal. I.e. a slave that is out of 5.8GHz range of the master will not display video even if it could technically pick up the aircraft's video signal.

By "synchronisation" you mean all the slaves have to be registered with the Master? That makes sense. I never got that far. I only have one master and one slave. I have never even seen another Inspire 1 in the wild, beyond my own.
 
By "synchronisation" you mean all the slaves have to be registered with the Master?
And be in range so they can continuously talk to each other. As I said as soon as a slave gets out of range of the master's 5.8 link (about 100m or so) it will lose video.
 
Sorry, have to correct you on that one.
The control AND video is transmitted over 2.4ghz using digital transmission for the video along with the standard 'packet' style control link with the usual parity and identity confirmation checks over frequency hopping spread spectrum.
The 5.8ghz link is nothing more than a 'bluetooth style' link between the master and slave to control the camera/gimbal etc.
The 2.4ghz is transmitted at the legal (UK) limit which is 100mw EIRP/20dB. Because the video is 'embedded' digitally it kind of gets round the 25mW limit that would otherwise be applicable for analogue 5.8ghz video transmission.
Hope that clarifies things.

I can confirm this with real-world tests I have conducted with my Inspire and 2 controllers. We were having video feed issues with the second (camera) controller. We had a signal booster on the first controller, which was receiving strong video feed. Adding the signal booster to the second controller fixed the video feed issues on the 2nd controller. Clearly, video is fed directly to both controllers FROM the Inspire.
 
Yep. BUT synchronisation is needed between the controllers for slaves to be able to pick up the video signal. I.e. a slave that is out of 5.8GHz range of the master will not display video even if it could technically pick up the aircraft's video signal.

This is good to know! I find DJI's claims of "300 feet between controllers" dubious at best. I'm usually within 30' of my pilot and have had some dropout issues even that close to each other. The cure is to stay within ear-shot of each other, which is something we want to do anyway.
 

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