frame loss issues

[Ballistic1]

OK this doesn't make any sense so I thought I would run this by other users to see if they have experienced this or I am just missing something? OK here goes
I decided to install a JR 921 receiver in my 260 ,I set it up and bind ed with smart-safe fail-safe
all is OK and all functions operate correctly.
Now I decide to range check the system and it passes all antennas show 0 fades, BUT the logger
shows 20 frame losses and also 0 holds
so I try it again but this time I am standing next to the plane watching the flight logger which is set to count frame losses and it is counting up as long as I hold the button on the module . I stand there and let it go to 55 It stops counting up if I release the button on the module.
I then check the antenna fades and all 4 antennas show 0 and 0 holds ??

so I try this 3 more times and its the same -no antenna fades ,no holds but frame losses continue
to count up while I hold the button on the transmitter module

any ideas

Frank

[1bwana1]

Very interesting numbers that could indicate how the system is working internally. I have no knowledge of the internals, but the following seems logical to me.

It is possible that an antenna "fade" indicates that the system has detected that the current receiver is losing frames, and needs to switch to another receiver that is getting a stronger signal. This switch is what increments the "fade" count. The algorithm may require either a certain number of consecutive frame drops, or a specific number of frame drops in a given time period, before it decides to switch. In this way, you could get a positive frame drop count, but still no fades.

The hold function is known to follow this model, in that it requires a certain number of consecutive frame drops before going into hold.

I would be interested to hear a detailed explanation from someone who has inside knowledge of the Spektum system, and it's algorithms.

[sweetpea]

I had always thought that fades where specific to each RX.

And that frame losses were where all RX's had a fade at the same time. And that it takes 45 frame losses in a row to equal 1 Hold.

With this information if you see 50 frame losses you may not see a hold because it doesn't tell you that those 50 were consecutive. Keeping that number below 45 would then give you piece of mind that your system is not near going into hold.


I'll be interested to see what you find out is the issue.

[1bwana1]

Sam,
You are correct on the 45 consecutive frame drops being required to cause a hold. I think we can be confident that a frame drop is when the system doesn't receive the next "packet" of data that it expects. The question we are trying to address is what constitutes a "Fade". It appears the system can have frame drops, and no fades. So a frame drop must indicate something other than a simultanious fade on all receivers.

[1bwana1]

Below is what Spektrum says, if it is correct, then Franks numbers should be impossible to acheive. Very curious.

Antenna fades – represent the loss of a bit of information on that specific antenna. Typically it’s normal to have as many as 50 – 100 antenna fades on any one of the antennas during a flight. If any single antenna experiences over 500 fades in a single flight, the antenna should be repositioned in the aircraft to optimize the RF link.

Frame Loss – represents simultaneous antenna fades on all attached receivers. If the RF link is performing optimally, frame losses per flight should be less than 20.

Hold – a hold occurs when 45 contiguous (one right after the other) frame losses occur. This takes about one second. If a hold occurs during flight, it’s important to re-evaluate the system, moving the antennas to different locations and/or checking to be sure the transmitter and receivers are working correctly.

[sweetpea]

Thanks Steve, that was the info I was getting my thoughts from.

What is possible though is a weak connection on from the logger to the RX.

I know I've seen my numbers jump all around if the connection isn't tight. Maybe that is what he is seeing.

[dick hanson]

Take a peek at the new 6 channel Carbon Fibre Spektrum rx
super trick setup
I have used a few logger but since I long ago figured out what is GOOD antenna placement I find no losses except for a piddlin few.
Mostly tho I use the DX7 rx - I do have the 9 channel setups but because I use many NON digital servos (by choice), the DX7 ,7000 rx works better no jump on connecting with these servos and the 1024 rx..

[phippsj]

Just run the range test just like the instructions say. Run it without the engine running, and then again with the engine running. Just have someone stand over the tail (assuming it's a large scale gasser).

After you make your walk-around with the bind button pushed (to reduce signal strength), then check the numbers on the logger. Don't stand right next to the plane with your radio to watch the numbers on the logger. You will get bogus info doing it that way. I had the same problem my first time as you.

Remember, you don't need the data logger plugged into the receiver for it to give the data readout at the end of a range test or flight. You can plug in the logger after the test or flight and read the numbers. The data is stored in the receiver, not the logger.

The best thing to do is set up a charge port in the wall of the fuse with an extension going to the data port, and use this to plug in the data logger after a test or flight. Of course, you have to remember NOT to turn off the power to the receiver, or the data will be lost.

As long as the fades and frame losses are within the range stated in the instructions, you are good. Holds are bad. You can re-position the antennes to maybe get the numbers lower, but don't expect to see zeros across the board every time.

I fly three planes with R921's, all giant scale gassers. Two are composites. I have had zero problems in the past 6 months since I converted everthing to Spektrum.

The data logger is a useful tool, but don't get totally hung up on the numbers it's giving you.

[DC Gayhart]

I have a similar experience when I first installed an AR9000 in my 1/3 Cub. The frame losses exceeded fades. I never really got a good explanation of why it happens. After many test flights, my frame losses are non-existent.

I agree with Jim, use good installation practices and don’t get to hung up on the Data Logger numbers unless they exceed the manufacturers recommendations.

[Ballistic1]

I decided to check my set up by replacing the 921 receiver with a spectrum 9000 and now all is well - no frame losses
while standing next to the plane in low power mode
It must be a problem in the receiver so I called Horizon today and will send it in as they advised
I have an identical set-up in a 40% 300 and I know what I should expect to see from the data logger numbers
and this just dosent seem right
I would rather be safe than sorry with a 40% airplane

[phippsj]

I have had several flights on my 35% composite plane that there were zero's all across the board on the data logger. That's makes me worried more than if I saw a spike in the number of fades and frame losses.

[Ballistic1]

that's just it there are no antenna fades from any antenna -just frame losses counting up to about 60 in 2 to 3 minutes and also 0 holds -45 consecutive frames lost should count as 1 hold

[Cobra1]

I too had these unexplained frame losses but after I sent in the receivers to get the fast reconnect feature all unexplained datalogger data went away. They are 7000 rcvrs and they have always worked perfect but when transmitter was close I would get a # of frame losses but no antenna fades. After the upgrade, no more frame losses up close - wonder why. Oh well, as long as they work I am happy.

[kiosk]

well instead of starting new thread figure add on this one.....I almost lost my P51 Sunday, had a good 2-3 sec lockout with X9303 and R921!!! it came back and was able to pull out safely but scared heck out me. The flight log showed 430 frame loses but no holds?? hell if that wasnt a hold I dont know what is. did range check after and was all good

anywayys sent the RX back to Horizon, not about to lose a $2000 bird with this nonsense.....has been working ok for 50 flights, voltage was 6+ on RX batteries

[bodywerks]

What wer your fades per antenna? We need pics of your install as well to better help you.
It takes 45(or something like that) consecutive frame losses to get a hold. JUst because you have that many frame losses (they are frame losses and not fades, right?) doesn't mean you have to have had a hold.
I had a similar incident where I had anywhere from 400 to 800 fades on my antennas, frame losses in the hundreds, had a very convincing loss of control of my plane for a couple seconds, but no holds were recorded. I am running redundant A123 batteries through no switches and was on landing approach so brownouts were ruled out. Then, after going through my system, I moved my antennas around, paying special attention to keeping them at least 4 inches away from metal, big pieces of carbon fiber(like my wing tube), AND MY FUEL TANK. I also only had my antennas on the x and y axis and none on the z. Changed that around as well and got major improvements. BUT, I also found that how my Tx antenna is positioned greatly affects my fade performance. I went from pointing it straight out to pointing it straight up and my numbers improved noticeably.