Telemetry lost

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Raythegreat
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Telemetry lost

Post by Raythegreat » Sat Oct 12, 2019 3:17 am

Hi all,

I know the subject of telemetry lost has been discussed several times before but I have special problem.

I've been using the X9d+ with a X6R receiver on a plane for 3 years now without problems. Made several flights.
Suddenly, since a few weeks,I have telemetry lost warnings when I taxi on grass. I was able to fly the airplane with no problems but when I taxi I get the telemetry lost signal and the controls are all obviously not working (motor does not work and AIL, ELE, RUD are frozen).

I have attached a picture of the receiver X6R in which I taped the two antennas with grey Duct tape (non metallic of course).
I also changed my ESC because I thought it was the culprit but apparently it's not.

I'm suspecting now the receiver X6R who worked fine for 3 years and I did not change anything. My Tx X9D+ works fine with other airplanes.

What can be the causes of telemetry lost in openTx Taranis besides being too close or too far.
My RSSI was at 65 db just before the telemetry lost and the plane was about 30 meters from me on the grass not moving.
I can produce this problem relatively easily and it only occurs on the ground (short grass) and not too far from me.

What can cause telemetry losses?
Please advise.

Thanks,

RTG
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kalle123
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Re: Telemetry lost

Post by kalle123 » Sat Oct 12, 2019 6:30 am

As always, it is a good idea, to have a look into the log file.

br KH

Carbo
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Re: Telemetry lost

Post by Carbo » Sat Oct 12, 2019 8:12 am

Raythegreat wrote:
Sat Oct 12, 2019 3:17 am
Suddenly, since a few weeks,I have telemetry lost warnings when I taxi on grass. I was able to fly the airplane with no problems but when I taxi I get the telemetry lost signal and the controls are all obviously not working (motor does not work and AIL, ELE, RUD are frozen).
Seems you lost not only telemetry but your complete RX. Presumably a hardware issue, most likely a loose power supply connection.

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jhsa
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Re: Telemetry lost

Post by jhsa » Sat Oct 12, 2019 9:48 am

Not at all a power supply problem :) because he only loses link when taxing the plane on grass and faraway.

I do have alarms when my.planes land on grass quite faraway from me, and that is quite normal because if the antennas are quite low under the plane, the grass can block the signal. Only the fact that the plane sits on the ground reduces the signal a lot. But if this problem didn't happen before, I would check antenna placement. Then I would do a low power range check. Place the plane on a wooden bench at about 1 meter high ( not on the ground), put your transmitter in range test mode, and walk away from the plane. If link is lost within a distance of about 50 meters, do not fly your model. A good range test can reach 90 to 100 meters without losing control completely.
If the receiver passes the test, look at antenna position. Is the model made out of carbon fiber? Are the antennas mounted at 90 degrees to each other? Are the antennas running paralel to pushrods, cables, or other metal parts? Are you pointing the tip of your radio's antenna at the model?(don't do this). The tip of the antennas has the weakest part of the signal. The side of the antenna radiates most of the signal. So never point the tip or the back of the antenna to the model. Always its side.

If all this checks ok, apart from the range test, you could have an hardware problem on your receiver. A lose antenna, a broken antenna, or other hardware problem.

But still, grass will also attenuate the signal.

João





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Carbo
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Re: Telemetry lost

Post by Carbo » Sat Oct 12, 2019 10:19 am

jhsa wrote:
Sat Oct 12, 2019 9:48 am
Not at all a power supply problem :) because he only loses link when taxing the plane on grass and faraway.
Hmm, sometimes taxing means also shaking the plane ;)


Raythegreat
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Re: Telemetry lost

Post by Raythegreat » Sat Oct 12, 2019 5:05 pm

Thanks for the answers.

I do not think I have a power supply issue but I will check this. The plane does recuperate the telemetry sometimes.
I agree with jhsa about the ground attenuating the signal but it was not like this before and the plane is close max 30 meters.

Let me answer JHSA questions:

I do have alarms when my.planes land on grass quite far away from me, and that is quite normal because if the antennas are quite low under the plane, the grass can block the signal.
rtg: the antennas are placed on the side of the airplane and the airplane is all wood, no carbon rods.

Only the fact that the plane sits on the ground reduces the signal a lot. But if this problem didn't happen before, I would check antenna placement.
rtg: the placement of the antenna has not changed and it worked before.

Then I would do a low power range check. Place the plane on a wooden bench at about 1 meter high ( not on the ground), put your transmitter in range test mode, and walk away from the plane. If link is lost within a distance of about 50 meters, do not fly your model. A good range test can reach 90 to 100 meters without losing control completely.
rtg: good idea to do a range test. will do.

If the receiver passes the test, look at antenna position. Is the model made out of carbon fiber?
rtg: No carbon, all wood. Pushrods are plastic. in a plastic tube.

Are the antennas mounted at 90 degrees to each other?
rtg. No but they are on the same plane but apart 180 degrees. Not ideal but acceptable.

Are the antennas running paralel to pushrods, cables, or other metal parts?
rtg: No nothing like that except the ESC cable to receiver is about 2cm from one antenna.

Are you pointing the tip of your radio's antenna at the model?(don't do this). The tip of the antennas has the weakest part of the signal. The side of the antenna radiates most of the signal. So never point the tip or the back of the antenna to the model. Always its side.
rtg: Yes I know that, the antenna is properly positioned, never the tip towards the plane. I know about that.

rtg: new info:
I remember now something I forgot to mention. Last year I was using the X9D and did not have this problem. This year I am using the X9D+ and got these problems but my X9D+ works well with all other airplanes.

So my candidates for troubles are:
1- antennas should be moved? No a lot of space.
2- Change the receiver and recheck.
3- maybe my X9D+ Tx RF module?

Thanks to all
RTG

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jhsa
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Re: Telemetry lost

Post by jhsa » Sat Oct 12, 2019 7:46 pm

If.the antennas.are.180 degrees, they ate not ideal. And if one points the tip to the radio, the other will point is back. Not good. Something else that influence the signal strength is moiture in the air.. A wet day means worse link.. There are many factors that can reduce signal strength..

João
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jhsa
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Re: RE: Re: Telemetry lost

Post by jhsa » Sat Oct 12, 2019 7:48 pm

Carbo wrote:
jhsa wrote:
Sat Oct 12, 2019 9:48 am
Not at all a power supply problem :) because he only loses link when taxing the plane on grass and faraway.
Hmm, sometimes taxing means also shaking the plane ;)
His plane would aready been destroyed if he flew it with some bad connection on the battery circuit :)

João
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Raythegreat
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Re: Telemetry lost

Post by Raythegreat » Sat Oct 12, 2019 8:05 pm

Thanks for the replies.

I do not think is is a power issue but it's possible. I will check this.
I had the problem, changed the ESC and still have the same problem. Maybe a bad wire. I will check this.

However, the behavior does not point to a power problem.
Sometimes the plane taxis well and suddenly I get this telemetry lost. Just before that the RSSI was around 65 which is enough even on the ground.
When telemetry lost occurs, I loose 100% of the airplane and sometimes telemetry recover can come back but never in a clean way.
I need to disconnect the ESC from battery to make it work again....and re-fail.

In openTx what are all the possibilities of getting a telemetry lost?

The ones I know are:

1- Too close
2- Too far but RSSI would confirm it.
3- Loosing power
4- Flaky RF link. Either Rx or Tx or antenna problem (placement, broken).
5- what about sensors? I have the Lipo FLVSS added on the smart port.
6- Others?

RTG

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Kilrah
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Re: Telemetry lost

Post by Kilrah » Sat Oct 12, 2019 10:32 pm

If you have telemetry lost AND no more control then your receiver lost the RF control link.
When it loses link it also stops sending telemetry, hence the telemetry lost.

So if power is eliminated it'd likely be either faulty receiver or TX module.

Raythegreat
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Re: Telemetry lost

Post by Raythegreat » Sat Oct 12, 2019 11:22 pm

Kilrah,

Yes I agree, either Rx or Tx or antenna placement border line.
My Tx X9D+ works with other airplanes with no problems so I will start with the Rx (change it) and see the result.

It might also be a combination of the X9D+ X6R and antenna placement and on the ground.
Last year I flew the same airplane several times with my X9D and same Rx and antenna setup. Never a problem.

Thanks all
Ray

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jhsa
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Re: Telemetry lost

Post by jhsa » Sun Oct 13, 2019 8:53 am

Ray, I have just thought of a test you could do to test if the receiver has a bad antenna.
You probably need to remove the rx from the plane, and probably need someone to help you..
The idea is to put the radio in range test mode (low power), separate radio and receiver a few meters so RSSI starts being on the low side. About 10 meters should be enough.
Now cober one of the rx antennas with your hand. Then cover the other. If.you lose link completely when you cover one of them, then the other is damaged.
The receiver has antenna diversity, and when one of the antennas has low signal, it switches to the other.

But before this do a range test as I suggested above. One thing you could do is also asking someone to turn your plane while you walk away so one antenna points directly at the transmitter at the time, while the other has its side facing the transmitter.

I am starting to think you have a faulty RX, or at least a faulty antenna. Or at least a bad connection between antenna and receiver..

João
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Raythegreat
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Re: Telemetry lost

Post by Raythegreat » Sun Oct 13, 2019 4:11 pm

Hi Joao,

thank you for your reply.

Your test is interesting. I will try that after range test.
I'm also starting to think that the Rx or antenna has a problem because the telemetry lost occurs only in certain conditions:

1- Taxiing (on the ground only)
2- relatively far, more than 10 meters
3- At a certain orientation.
Once the RF link is lost I need to power off and on the ESC to recover. When it says telemetry recovered, the controls are weird (throttle starts at 50%).

In fact Kilrah is right, the problem is not a telemetry lost but more an RF link lost because I lose completely the control of the airplane.
But just before the telemetry lost RSSI was at 65??

But what is so puzzling is why now? why suddenly? I did not touch anything and did not crash or land hard the airplane.
Remember last year I did not see that problem with my X9D and I did not change the setup this year except change the ESC.

Do you think the grey duct tape could have metallic particles or wires in it?

RTG

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jhsa
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Re: Telemetry lost

Post by jhsa » Sun Oct 13, 2019 7:19 pm

Raythegreat wrote:
Sun Oct 13, 2019 4:11 pm

Once the RF link is lost I need to power off and on the ESC to recover. When it says telemetry recovered, the controls are weird (throttle starts at 50%).
Only when link recovered? what about when it is lost? Did you set failsafe? You should..
In fact Kilrah is right, the problem is not a telemetry lost but more an RF link lost because I lose completely the control of the airplane.
That I understood yes, it loses link, I think I also mentioned it above.. Or maybe not :)
But just before the telemetry lost RSSI was at 65??
If I understand what you mean here, yes, this is weird and could point to a worse hardware failure than just an antenna. Please, if you care about your plane do not fly it with this receiver, at least until you find out what the problem is, and solve it.
But what is so puzzling is why now? why suddenly? I did not touch anything and did not crash or land hard the airplane.
Remember last year I did not see that problem with my X9D and I did not change the setup this year except change the ESC.
Was the plane stored in a place with a lot of moisture?
wait there a second, perhaps Carbo was right after all. :) I might have missed this, you say you only changed the ESC, and you taxing when that happens. Is it a nose wheel plane?. Anyway, if the ESC is weaker than the one you had before it could happen that when you taxi on the grass the servos are drawing too much current, the voltage drops and the Receiver stops working (Brown Out). That could explain link lost at an RSSI of 65.
Please do a simple test, move all the servos at the same time and see if you lose link..
Do you think the grey duct tape could have metallic particles or wires in it?
Not sure, if it has carbon in it, it could be a problem..

João
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Raythegreat
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Re: Telemetry lost

Post by Raythegreat » Mon Oct 14, 2019 1:49 am

Hi Joao,

I was not able today to get this telemetry lost. I have to say it was a dry day, no clouds, pretty dry October day.
But I'm discarding this possibility of dry vs humid day to explain my problem.

I did a range test today and all seemed OK. While in test range situation, I was able to walk 75 meters (1 big step = 1 meter) without getting a weak signal and got telemetry was lost only after 80 meters and more. Also my antenna was pointed towards the airplane and antennas inside plane pointing towards Tx. So pretty good range test in the worst situation possible. Plane was on the ground (grass) not moving.

I then moved all the wires to see if there was an electrical power intermittent problem and nothing, all wires were solid. No power loss.
BTW I changed my ESC because I had the telemetry lost before and thought is was an ESC problem. So my ESC is brand new.
I then moved one antenna just a little bit and the RSSI was up by 3 db which is not bad.

My conclusion is either bad antenna placement and/or receiver is faulty.

I will change my receiver and place the antennas at 90 degrees.

One question about the antennas: One of my RC friend told me the useful antenna length is only the 1.5 inch at the end of antennas? The rest is only a wire for the antenna. Is this correct? The region where the antenna does not have the black wire covering?
If this is true, this is good news. I can re-arrange more easily.

RTG

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jhsa
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Re: Telemetry lost

Post by jhsa » Mon Oct 14, 2019 1:54 am

yes, the antenna itself is the end that is not shielded..

João
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Re: Telemetry lost

Post by Raythegreat » Mon Oct 14, 2019 5:21 pm

Thanks João for your all answers and input.
All interesting.

RTG


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