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Video Transmission Signal Strength vs. RC Transmission Strength
771 7 2017-5-12
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BearDrone
lvl.4
Flight distance : 2887251 ft
United States
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When I am occassionally flying my P4, I notice I get a warning across the top and in red on the screen of my iOS device that says, "Warning Weak Transmission Signal". The screen usualy starts to pixilate or hang. I then promptly 180 the craft, bring it closer to home,  and all is well.

When I look at the signal strength indicators at the top, both seem to be full bars, strong signal.

I am flying at sea level, literally, from the beach on the Atlantic. There are no obstructions. I usually get this signal when I am about 4,000 ft. away in distance. This is a far cry form the stated 5.2K (3 miles or approximately 15,000 ft.) range in the specifications of the device.

So, is the Go App telling me the transmission signal for the video is weak, or the signal from the RC that is controlling the craft? Are they one in the same?

Why am I getting such a short range? You can't get anymore unobstructed, flat, and line of sight than flying directly out towards the ocean.

Thanks,
2017-5-12
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Mark The Droner
Captain
Flight distance : 2917 ft
United States
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My guess is the warning is for your FPV / telemetry signal which is independent of your control signal.  

You say you are LOS and only 4,000 feet distance over the ocean.  You say the signal is strong, and yet you get the warning of a weak signal.  How can this be?

LOS is sometimes not good enough.  

https://en.wikipedia.org/wiki/Fresnel_zone

The signal may be strong but it's getting interference from itself because the deflected signal off the water is out of phase with the primary signal.  The fix is to be sure the water is not in the first fresnel zone.

For example, standing up near the water with your controller is better than sitting down near the water with your controller.  Standing on a pier with your controller is better than standing on the beach with your controller.  Etc.

Increasing the altitude of your P4 will help too.  
2017-5-13
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BearDrone
lvl.4
Flight distance : 2887251 ft
United States
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It is odd. I do increase my altitude to the 400 ft. max that is allowed, but it does not help. I may try flying out to sea at different angles to see if that makes a difference. I could also be getting EMI from multiple military installations that are in the area, but not in the near vicinity. Yes, I am flying legally where I am.

I just thought flying out over the water would be the best case scenario for the transmission range of the two units. I am generally standing on the back of the beach near the dunes while I am flying.
2017-5-14
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Geebax
Captain
Australia
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BearDrone Posted at 2017-5-14 17:38
It is odd. I do increase my altitude to the 400 ft. max that is allowed, but it does not help. I may try flying out to sea at different angles to see if that makes a difference. I could also be getting EMI from multiple military installations that are in the area, but not in the near vicinity. Yes, I am flying legally where I am.

I just thought flying out over the water would be the best case scenario for the transmission range of the two units. I am generally standing on the back of the beach near the dunes while I am flying.

The system has two completely separate radio transmission systems, one for control of the aircraft and one to return the FPV video signal. The signal strength indicators on the top status line are showing the control signal strength, and the message is referring to the returned video signal. Usually the control signal works at a longer range than the video signal. The advertised range is very optimistic and can only be achieved under absolutely ideal conditions, and chances are, you won't ever get that range.
2017-5-14
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Mark The Droner
Captain
Flight distance : 2917 ft
United States
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BearDrone Posted at 2017-5-14 17:38
It is odd. I do increase my altitude to the 400 ft. max that is allowed, but it does not help. I may try flying out to sea at different angles to see if that makes a difference. I could also be getting EMI from multiple military installations that are in the area, but not in the near vicinity. Yes, I am flying legally where I am.

I just thought flying out over the water would be the best case scenario for the transmission range of the two units. I am generally standing on the back of the beach near the dunes while I am flying.

If in fact the fresnel zone is causing the disappointing distance problem and you can't fix it by changing the height of your transmitter, you could also fix it by changing to horizontal polarity - which would not only remove the interference, but also give you a signal boost.
2017-5-15
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BearDrone
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Flight distance : 2887251 ft
United States
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Mark The Droner Posted at 2017-5-15 02:33
If in fact the fresnel zone is causing the disappointing distance problem and you can't fix it by changing the height of your transmitter, you could also fix it by changing to horizontal polarity - which would not only remove the interference, but also give you a signal boost.

How do I change to horizontal polarity? I'm not following your suggestion.
2017-5-15
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Geebax
Captain
Australia
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Mark The Droner Posted at 2017-5-15 02:33
If in fact the fresnel zone is causing the disappointing distance problem and you can't fix it by changing the height of your transmitter, you could also fix it by changing to horizontal polarity - which would not only remove the interference, but also give you a signal boost.

That would involve a lot of modification, as you would have to change the orientation of the aircraft antennas as well.
2017-5-15
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Mark The Droner
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Flight distance : 2917 ft
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Yes.  It means you need to point your antennas horizontally instead of vertically so that the wave moves left to right instead of up and down.  That way when it bounces off the water, the receiver will see a strengthened signal due to in-phase deflection instead of a weakened signal due to out-of-phase interference.  

RE the mod, maybe not so hard on the controller but a major mod on the bird side.  I'd likely go with a dipole on the AC.  That way you can bend it exactly the way you want it.  It can be done but it would be a lot of work - especially on a P4.  And then when you're done you might find out I'm full of it and it didn't help.  Because I've never seen a side by side comparison of this kind of flight which makes it kind of theoretical.  But in theory it would work.  See the fresnel zone wiki page where it discusses polarity.
2017-5-15
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