sudden dive

[erhard52]

The amount time before entering failsafe can be programmed.  2 seconds is the default.  As soon as the signal is available failsafe is exited.

Again, failsafe set to HOLD will not change the servo positions while a failsafe is occurring.  A failsafe set to USER DEFINED will hold the failsafe at whatever positions you have deliberately set them to.  You should be setting the failsafes to some known position.  We typically recommend slight up elevator, and either slight left or right rudder.  Failsafe is not designed to save an aircraft - it is designed to give you predictable flight path where you can determine where a loss of radio control impact will occur so that people can be moved.

We are still selling products, and doing upgrades and repairs, so people are still using XPS radio systems.

i understand the setting  and i remember an article from the 70ies  the title was - "crashing with or without failsafe".
my problem is that the planes see to get down as if you suddenly push the elevator down because i cannot really explain this behavior with turbulences etc - wish o had a movie of it. one time i think it was diving more than 2 seconds from higher up and then reacted to my elevator pulling.

it is also interesting that it happened on traditional tails and vtails which would require 2 servos go in sync for the vtail or it would be more like a rudder effect. anyways, weird.
then again there is always pilot error too

erhard

[erhard52]

so today i flew with the new setup (spectrum DX6i + AR610) and all went well - 3 flights and nothing unusual happened where i felt i had a delay in response etc. i also put the plane purposely into a dive and it did not recover on its own but responded immediately to up-elevator.
so that leaves my in limbo with my XPS setup. it is sad because the multiplex evo 12 is a much more capable transmitter than the dx6i.
also the previous dives happened with the 10CH XPS receiver but as i said i forgot to mount the transmitter antenna after range test. so different receivers leads to the transmitter module as problem. i wish i could find my XDP to do further investigations.
i think i should also repeat the range test with both systems and compare.
any other suggestions?

so i did the range test for spectrum and XPS
both on full power (no range check mode, model was inside house and i walked outside)
spectrum range is about 2x than XPS (in XPS i used the NANO receiver)
it seems with XPS there is no difference when pressing the external prog. button on the transmitter for reduced power - or does only the internal prog button work for this?

i also double checked the power level mode and it is set to 5 which i assume is the highest one.

the range test was done in the same plane just the receiver was swapped out and i used a webcam to monitor the rudder motion.

[XPS]

There is no "external" prog button for the EVO radio with the XtremeLink module. Which actual EVO model are you using? What version EVO firmware you using? Did you get our module updated for the EVO radio?

Are the antenna wires on the Nano completely straight out, 180 degrees from each other? How is the Nanon mounted? Glider installations are tricky because there is very little space. Most people use the RFU and X10+ with glider setups because the RFU has dual long antennas that can be placed anywhere. The Nano requires very strict mounting requirements.

[erhard52]

There is no "external" prog button for the EVO radio with the XtremeLink module.  Which actual EVO model are you using?  What version EVO firmware you using?  Did you get our module updated for the EVO radio?

Are the antenna wires on the Nano completely straight out, 180 degrees from each other?  How is the Nanon mounted?  Glider installations are tricky because there is very little space.  Most people use the RFU and X10+ with glider setups because the RFU has dual long antennas that can be placed anywhere.  The Nano requires very strict mounting requirements.

i have the royal 12 evo. yes, the wires are straight out on the nano. for the range test the nano mounted as photo shows.
hope the photo works because when i copy the link in the mask it does not work

nano mounting.jpg

this is the EVO. i do not have the description anymore  but there was an update that made these external buttons work  so one did not have to open the transmitter anymore.
clearly the binding works this way. 
my FW is 3.46 for the evo

evo royal 12 -XPS.jpg

is there still a way to get an XDP module from somewhere - i checked ebay, FB nothing

i want to add that i do have an RFU and X10 but this is a small glider but i can try the range test with it. i also have the XPS RF module for the hitec radio and can bind that one and try the range test

[XPS]

OK, so you are using the EVO's bind and range test options. You should see a substantial difference in the range test. When the EVO is in range test mode (beeping and showing RANGE on the display) the power output is only 0.19mw. However, the Nano's range can be several hundred feet with this power when doing the range test correctly (model at least 1 foot off of the ground) in the case of aircraft that have no landing gear. When you stop the RANGE test mode and go back to full power, the range will be 41.2 times further. So, if you got 100 feet in your range test before intermittent control started occurring, your full range would be about 4120 feet. We typically see about 400 feet with the Nano on dry ground.

The installation you have is not good though. You can't have wires passing under the antenna halves. Those antenna wires create a single antenna... that's not two antennas. So, wire(s) passing between the wires, especially if they can ever move (even a small amount) will de-tune the antenna. Moving wires are devastating, and the receiver can actually disconnect from the transmitter. Failsafe will hold the servos at their last known position or positions you have defined when this occurs. You won't ever get uncommanded input. You would be better off moving the receiver either up into a vertical stab or into the nose. Small installation like this are difficult to work with and were never the focus for this product line.

[erhard52]

ok
1. i accept your suggestion for the receiver location but i want to mention that the ar410 i mounted the same way and i flew again today with no issues.
2. thanks for mentioning the range test - i noticed i did it wrong - i need to push the prog button before i turn on the transmitter which i forgot. and then i see the RANGE message on the screen. that explains that i did not see a difference when i just pushed the button while transmitter was on - it always was in full power and i saw not difference that at least that was consistent.
3. see attached pics. i use my mini spectrum analyzer set to center frequ=2.4GHz and span 200MHz. so a lot of bouncing pics as the pics shows.
a) now when i turn on the EVO i see barely a difference in the max peak (around -50dBm)
b) i turn on my optic6 hitec with XPS rf module and the peak goes to -30 - -25 dBm
c) spectrum dx6i peak up to -20dBm.
so i would conclude that the EVO output is the weakest and the optic 6 and dx6i about equal and much higher.
it seems they all do the frequency hopping but the weak evo output i do not like.

if i use the RFU unit where would i mount that one ? do the antenna wires need to be away form each other?

the NANO receiver is considered a full range receiver correct, not only of park flyers

you never answered my question about the XDP availability

thanks
erhard

https://photos.app.goo.gl/pVxioLNzkgN9WZF56

[XPS]

That AR10 is an integrated antenna, likely not passing over your wires or split.

Your spectrum analyzer is likely too slow to be measuring signals. The entire band should be saturated. R/C systems will use the entire band from 2.405GHz to 2480GHz.

Power means very little when it comes to communications. Every 6dB of receiver sensitivity doubles the effective range, but it takes 4 times the output power to double the effective range. XPS receivers are extremely sensitive, and have excellent noise rejection (besides the normal rejection that spread spectrum offers). All XPS RF modules output the same power. Make sure that your antenna is not cross-threaded as that can significantly reduce the output power (partial shorting of the antenna).

The Nanos are full range, but the RFU receivers have even higher sensitivity, so their range is longer. The antennas should be located 90 degrees from each other for the best possible reception. Those are two separate antennas, which provides spacial diversity.

The XDP has not been available for about 8 years. You can make an XDP by using our Serial Link (used for expander products) with a Nano receiver. The Serial Link was also discontinued by our supplier a few years after the XDP.

[erhard52]

thanks for the response

not sure i understand your 6dB thing - 6dB is 4x power
attached my cable layout in the evo - should be ok

so would the serial link than work with the XDP program?

btw i flew again several times with the spectrum setup and had no unusual behavior during the flight. it makes me sad that i cannot use the evo/XPS anymore in good faith. i will try to relocate the nano away from the wires -

i am using the TinySA spectrum analyzer and could not find any good info on the web on how to measure FHSS power output

https://photos.app.goo.gl/eDtFKbY5H6ge3Zk87

so even with the assumption that my problems come from poor reception it still does not explain why the models went into this dive because if i turn off the transmitter the failsafe leaves the last servo position. nevertheless the RF communications seems to play a big role based on the no issues with the spectrum system

[XPS]

Let's say you are using the same transmitter that has an output power of 100mw EIRP with 2 different receivers - one has a sensitivity of -92dBi and the other receiver has -98dBi of sensitivity. If you get 1000 feet of range out of the receiver with -92dBi of sensitivity you will get 2000 feet of range out of the receiver with -98dBi of sensitivity. You can also get 2000 feet of range with the receiver having -92dBi of sensitivity if you make the transmitter's output power 400mw (4x the power). The FCC does not allow that high of power though because there is no way possible to pass spurious emissions and peak power limits. The only way to increase range is to have very sensitive receivers.

You are using a different transmitter with the Spektrum setup. This could be something as simple as a pot that is dirty, which can cause exactly what you describe.

[flyingw]

Erhard,

Please consider the possibility that you experienced some temporary lockouts. These can happen when the line of sight between the transmitter and receiver is blocked by equipment and or other parts in the airplane. The XPS system will hold a servo at the last position for which it saw a good control signal. If the receiver receives a good signal again before the two-second failsafe timer expires, then no failsafe is declared and the system continues on from there. If the receiver does not see a new signal by the time the failsafe timer expires, then it (or the X10) will declare a failsafe condition and put the servos into whatever "User" positions you configured. Or, it will leave them in the last known position if you configured "Hold" as the failsafe output. I determined that in my case my system never went into failsafe while flying - I felt only the short gaps in control.

These equipment and parts that can block the signal includes servos, servo wiring, metal landing gear struts, ESC and wiring, batteries, and carbon fiber parts. I had a plane with which I experienced temporary lockouts and the problem was repeatable with two different radio systems - Futaba and XPS. Turned out it wasn't the radio system, it was the location of the receiver antennas relative to that other stuff.

I could reproduce the problem by setting my transmitter on a chair in low power mode, and then walking the airplane away from the transmitter until the system went into failsafe. Just before reaching that failsafe distance, I tilted the airplane into differing orientations with respect to the transmitter. I found an orientation where failsafe came much closer than the failsafe check distance (about 100 to 150 feet). It was just about the same orientation that the airplane was when in flight and I experienced the lockouts.

I ultimately located the receiver antennas (dual antennas on the RFU) with one element pointing aft, and the other pointing down and out through the bottom of the fuse. The element pointing down below the fuse was "out of the way" of the large aluminum landing gear part. After relocating the antennas out of the way of the other stuff in all orientations I haven't had the problem since. I'll bet the XPS Nano would have also worked fine if I placed it below that big aluminum landing gear.

Paul