90m altitude - weak/no signal?

[Proud_Hufflepuff]

I had the Phantom out for the second time today, and I took it out of beginners mode for the first time.

I was in two areas where there shouldn't be any interference, and I was able to get up to about 90m altitude (a few metres away from being directly above me) before I got weak signal warnings, and a couple of times a brief no signal warning.

Is this normal? Or should I be expecting more?

Also theres a definite whistling/whining noise when I'm flying, especially when heading upwards. Is this anything to be concerned about?

 

[PaulSouthport]

When directly above the antennas are not in the correct alignment, so yes it's to be expected. You need to have the antenna facing side on and roughly parallel to the legs, as per the manual.

Can't comment on the noise without hearing it.

 

[Proud_Hufflepuff]

When directly above the antennas are not in the correct alignment, so yes it's to be expected. You need to have the antenna facing side on and roughly parallel to the legs, as per the manual.

Can't comment on the noise without hearing it.

Ah I didn't know that. So with the drone further away from me I should be able to get more height?

I'm going to try to fire the motors without props tonight to try and identify the source of the noise. I'll take a video as well if I can.

 

[PaulSouthport]

Correct, but bear in mind the max height allowed depending where you are. You don't want to be mixing it with real aircraft!

 

[rockydog]

When the drone is directly above you, you need need to have the antennae parallel to to the ground so that the flat side is facing upwards.

 

[grin factor]

I think the noise you talk of is normal. Its the blades pushing the wind/air. Mine makes the same sound

 

[Paul Sw]

Long time lurker but first time poster. I must correct an error that I have seen several times. To transmit the maximum signal between the A/C and controller the controller directional beam must be pointed at the A/C. In addition the polarization of both antennas must be the same. When a few hundred feet away at a low altitude the antennas are parallel, that is they are both vertical. However, when overhead, as in the fine picture by rocky dog, the beam is pointed at the A/C but the polarizations are exactly wrong. There is really no way to maximize both the signal strength and the polarization with the given configuration. It probably makes little difference how the controller if held when the A/C is directly overhead. Either position is wrong for either signal strength of polarization. Its probably just a well that it quits below 400 ft. directly overhead.

Paul

 

[rockydog]

Long time lurker but first time poster. I must correct an error that I have seen several times. To transmit the maximum signal between the A/C and controller the controller directional beam must be pointed at the A/C. In addition the polarization of both antennas must be the same. When a few hundred feet away at a low altitude the antennas are parallel, that is they are both vertical. However, when overhead, as in the fine picture by rocky dog, the beam is pointed at the A/C but the polarizations are exactly wrong. There is really no way to maximize both the signal strength and the polarization with the given configuration. It probably makes little difference how the controller if held when the A/C is directly overhead. Either position is wrong for either signal strength of polarization. Its probably just a well that it quits below 400 ft. directly overhead.

Paul

The picture I posted was taken from the DJI manual....you may disagree with it, but I can assure you that in practice, it works.

 

[Proud_Hufflepuff]

I think the noise you talk of is normal. Its the blades pushing the wind/air. Mine makes the same sound

This is a separate sort of high pitched noise though. I'm just concerned that it may be a motor getting to give out.

 

[RodPad]

@Proud_Hufflepuff
Please read this post, thread and replies.
Phantom 3 standard Rc signal lost

Rod

 

[120CCPM]

Long time lurker but first time poster. I must correct an error that I have seen several times. To transmit the maximum signal between the A/C and controller the controller directional beam must be pointed at the A/C. In addition the polarization of both antennas must be the same. When a few hundred feet away at a low altitude the antennas are parallel, that is they are both vertical. However, when overhead, as in the fine picture by rocky dog, the beam is pointed at the A/C but the polarizations are exactly wrong. There is really no way to maximize both the signal strength and the polarization with the given configuration. It probably makes little difference how the controller if held when the A/C is directly overhead. Either position is wrong for either signal strength of polarization. Its probably just a well that it quits below 400 ft. directly overhead.
Paul

What you have seen several times is not an error. Keeping the RC antenna parallel to the ground maximizes the signal going straight up (the theoretical radiation pattern of an omni-directional antenna is a donut wrapped around the antenna itself, so near-zero signal along the antenna's axis, maximum signal on the perpendicular plane), which is definitely better than keeping the antenna pointing at the AC. Even if the receiving antenna is in the worst possible position (pointing straight down at the RC), the orientation of the transmitting antenna does indeed make a difference.

 

[SkyHog]

I don't disagree with anything said above, at least in terms of theory. However, in the real world, the actual radiation patterns and the actual signal polarization are not exactly like the idealized patterns we talk about in our diagrams. In the real world there are reflections, and imperfect antenna construction, and a dozen other factors that cause signals to propagate differently than expected, which sometimes helps, and sometimes hurts.

In theory, we can completely shut down the link, just by cocking the transmitter to the right by 90 degrees which creates cross polarization. But it the real world, we probably get less than 30 db of isolation by doing that, and stray reflections can keep the link humming along nicely.

We want correct polarization when we can get it. However, when I have the bird directly overhead, I find that I get best results by keeping the radiation levels high (i.e. RC antenna parallel to the ground), which seems to overcome any degradation due to cross polarization. It works..... even though theory says there should be zero antenna coupling when the bird is directly overhead. But the ground isn't perfectly flat, antennas aren't perfectly straight, and the bird is never perfectly overhead anyway. Reflections help in this case.

 

[120CCPM]

Which is exactly what I said...

 

[SkyHog]

Which is exactly what I said...

Which is why I said I don't disagree. I was addressing the comment on polarization.

 

[Paul Sw]

Sky Hog, you are quite right about reflections and degrees of cross polarization response in both antennas. However, what people are overlooking is the range we are talking about...less than 400 ft. Even if it were legal or advisable to fly straight up one kilometer, I doubt if the data link could be maintained. Either the antenna pattern or the polarization would be wrong. You cannot maximize both while flying directly overhead. You can demonstrate this by flying straight out some distance and then rotating the RC 90 degrees around the line of sight. That puts the transmitting antenna and receiving antenna polarizations orthogonal to each other. Without having done the experiment I predict the range will be reduced by a large amount, perhaps to a few hundred feet.

Paul

 

[rockydog]

Without wishing to sound rude, can I suggest you put your theories to a practical test, and then come back with your findings. I have personally flown to 600 feet directly above me -( which is legal if you're flying FPV and have a spotter with you)- ,and the GO app was still showing full signal strength. That was with the antennae parallel to the ground.

 

[SkyHog]

I have flown straight up several hundred feet, without much problem. Don't know the max I've flown that way, but I routinely come back 300 ft over home with no problems. Sometimes it does get flakier at high altitudes directly overhead. I can believe 600 ft is much harder. Nowhere near the distance you can get with any kind of horizontal distance.

 

[120CCPM]

Sky Hog, you are quite right about reflections and degrees of cross polarization response in both antennas. However, what people are overlooking is the range we are talking about...less than 400 ft. Even if it were legal or advisable to fly straight up one kilometer, I doubt if the data link could be maintained. Either the antenna pattern or the polarization would be wrong. You cannot maximize both while flying directly overhead. You can demonstrate this by flying straight out some distance and then rotating the RC 90 degrees around the line of sight. That puts the transmitting antenna and receiving antenna polarizations orthogonal to each other. Without having done the experiment I predict the range will be reduced by a large amount, perhaps to a few hundred feet.

Paul

Paul, nobody is overlooking anything. We all agree that flying directly above the RC puts the AC antenna in the worst possible orientation and you will likely not break any distance record going straight up. That's not the point, though. What we are all telling you is that, in those situations where the AC ends up right above the RC (for example, if you want a straight-down shot), keeping the RC antenna flat in order to maximize its signal in the direction of the AC is a good and proven practice (not an "error" as you called it) and greatly improves your chances to maintain control. That's all.

 

[Paul Sw]

You guys are really touchy... I was just trying to point out that in addition to the RC antenna being perpendicular to the line of sight it is also necessary to have both dipoles parallel to each other. An impossibility when flying directly overhead. The latter did not seen to be common knowledge. Reading back, post #2 actually said it correctly. I will go back to lurking.

 

[120CCPM]

Sorry if I sounded "touchy", but it seemed to me we were going in circles, you repeating that antennas must be parallel for best reception, myself and others insisting on correct orientation of the RC antenna. All in all, we're all saying the same thing, and hopefully the OP got some practical advice as well as a theoretical explanation.