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L9R failsafe for unknown reason.

#1
Hi,
I bought a 2nd hand Taranis and LOVE IT, huge improvement over my basic beginners radio. It came with a bunch of receivers, one of which was an L9R which i mounted to my fpv Simple Cub. However it failsafed after launch (ok maybe my transmitter got too close or something?) Then again at about 100m distance. The failsafes happen at the beginning of this video, and at 4:20

What would the cause be, do you think? I've got the L9R antenna in a V under the wing (visible in the photo at the end of the video). To close to VTX maybe?

The only other reason i could think was that there is an R9M module in the back of my transmitter with it's antenna attached (obviously this module is disabled) I had both antennas next to each other, parallel. Would that affect things?
 

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Ihichi Bolls

Well-known member
#2
I never put my receiver antennas on the same plane. One will always be vertical for normal flight the other will either be pointed aft inside the plane horizontally or parallel out the side on a wing.

Also I never point the radio transmitter antenna straight up. You are always pointing the radiation pattern dead zone at your aircraft... the weakest part of the signal.
 
#3
I never put my receiver antennas on the same plane. One will always be vertical for normal flight the other will either be pointed aft inside the plane horizontally or parallel out the side on a wing.
Great info, but I'm just surprised that even with the worst case scenario antenna orientation that the L9R failsafed at ~100 metres. Even more so that it lost connection at launch <10 metres. Wonder if something else is playing a part? I'll try range testing from various angles maybe?
 

Ihichi Bolls

Well-known member
#4
You technically "should" be doing 360 degree range testing already. :p

I know... its not the 70's and most gear is reasonably trustworthy.

As far as failsafes really close I have had them. Most times on boot up. I get the telemetry lost message if I boot the craft too close to the radio.

It depends where your antennas are in refrence to the transmitter. If both antennas are on the wing the deadzones will be pointing at you most of the time as you pass by parallel to yourself.

Get one vertical and make sure the other is not nested with servo wires or where signal can be blocked.

Depending on your radio you could probably program in verbal rssi warnings to let you know of potential issues too.
 

FDS

Well-known member
#5
Also check that the firmware in your TX matches the RX. Flex firmware works well on R9. I have it on mine, had no issues at all. I used the latest Flex on module then I keep the RX firmware on the radio and flash every one I buy, regardless of what it says it shipped with.
 

Ihichi Bolls

Well-known member
#6
@FDS The L9r reciever is not part of any 900mhz system it is 2.4ghz made for long range with Taranis system.

The only thing I can think of other then placement is that the tiny connectors inside the reciever have come off on one side making failsafes more random.
 

FDS

Well-known member
#7
I get them confused.
Those IPEX connectors on the antennas are annoying, they do come off easily. Thanks for the correction, post edited.
 
#8
You technically "should" be doing 360 degree range testing already. :p

I know... its not the 70's and most gear is reasonably trustworthy.

As far as failsafes really close I have had them. Most times on boot up. I get the telemetry lost message if I boot the craft too close to the radio.

It depends where your antennas are in refrence to the transmitter. If both antennas are on the wing the deadzones will be pointing at you most of the time as you pass by parallel to yourself.

Get one vertical and make sure the other is not nested with servo wires or where signal can be blocked.

Depending on your radio you could probably program in verbal rssi warnings to let you know of potential issues too.
The L9R doesn't (i don't think) have telemetry, but when i got my taranis ialso got a couple of R9 Slim+ receivers so i might try one of those and switch on logging so if i DO get a failsafe I'll have a better idea of why. FDS: on the R9 transmitter and receivers I've already updated to the latest flex firmware. I've not flown it yet, but i drove my car 5km away and it worked despite no direct line of sight, so I'm impressed.

I'll also try moving the antennas on the L9R, as I'd like to learn good antenna placement and better know the limitations of the hardware.

Thanks all!
 

FDS

Well-known member
#9
Make sure they are in different poles to each other, ideally 90 degrees apart and well away from esc’s, motors or batteries. So if you have one sitting horizontal out the side on a wing, the other might sit vertically out the top of the fuselage.
Remember the null field is like the hole of a donut, over the end of the active part of the antennae. Simplified view.
Same applies to RX field to an extent.
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#10
Make sure they are in different poles to each other, ideally 90 degrees apart and well away from esc’s, motors or batteries.
I assume the PCB antennas on the L9R have a similar donut radiation pattern? Mine came with a v-shaped mount like this and I notice that each antenna is not only at 90degrees to each other, but also rotated 90degrees along the length which I thought was interesting.
 

FDS

Well-known member
#11
If you look at the antennae planes in that they are at 90 deg. The flat edges show the direction. I think the blade antennae on that RX are not a simple dipole. I suspect it’s more like a double ended T shaped radiant pattern.
That mount would work on a wing, it might not be as good on a plane, especially if you have space to put the two apart and on different planes, it would possibly be better?
@Hai-Lee knows a lot about radio receivers.