RFU - diversity receiver for X10+ - Page 5 - RC Groups
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Jun 03, 2017, 08:29 PM
I have a X10 control program that I have been working on forever, and that will give you the other controls. I am working on the X24 control program at the moment. Once it is done, I might go ahead and finish up the X10 control program.
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Jun 27, 2017, 01:08 AM
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FlyingW's Avatar

RFU SBUS Failsafe Behavior


I am preparing an airplane for which the receiver will be an RFU. The RFU will output SBUS to a Navio2 flight controller.

I configured the RFU to talk SBUS and the Navio2 sees the channel movements.

Using the XDP program I set the throttle channel to turn off when in failsafe. It appears that with the RFU in failsafe, the throttle channel goes to 1500us.

Is this how the RFU should behave with SBUS when in failsafe? I thought OFF in SBUS meant no signal at all.

This might an ArduPlane setting or behavior that I do not yet understand. In any case I want to understand exactly how the RFU with SBUS will behave in failsafe.

Please clarify how the RFU outputting SBUS should and will behave when in failsafe.



p.s. Update: I read more and remembered that you set the SBUS failsafe flag(s) to signal a failsafe condition. I do not know yet if Ardupilot reads those flag(s) as part of its failsafe logic.
Last edited by FlyingW; Jun 27, 2017 at 10:25 AM.
Jun 27, 2017, 02:10 PM
Yes, the SBUS protocol itself has flags that determine the state of channels 17 and 18, lost frame, and failsafe. There is no "signal off" possible with SBUS.
Jun 27, 2017, 05:26 PM
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FlyingW's Avatar
Thanks Jim. Now to figure out whether ArduPilot uses the SBUS flag(s).

In the meantime I had the RFU capture the failsafe settings with the throttle channel 3 set down to 950us in the transmitter. I configured Ardupilot to declare a failsafe condition when it sees less than 975us on channel 3.

Then, for normal operation I reset the throttle channel range in my transmitter from 1100 to 1900us.

In comparison, the Eagletree Vector simply uses the SBUS failsafe flag.
Last edited by FlyingW; Jun 27, 2017 at 05:32 PM.
Jun 28, 2017, 12:39 PM
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FlyingW's Avatar

Does the RFU emit any RF energy when the telemetry is turned off?

I found my Navio2/GPS to be very sensitive to emissions from my 2.4GHz (XPS 9C module) transmitter. If I move it closer than two feet the GPS will not acquire satellites.

Just want to understand if the RFU is contributing to the RF activity in the area.


Jun 28, 2017, 01:21 PM
Yes, the RFU (like all XPS receivers) transmits an ACK response to the transmitter module for every packet received. This is one many things that sets our system apart from all others.

Remember, hobby GPS recievers have incredible sensitivity without much regard to selectivity, so they can be affected by spurious emissions. A proper GPS receiver can use Bluetooth communications without any adverse effects.
Last edited by JimDrew; Jun 28, 2017 at 10:48 PM.
Jun 28, 2017, 01:57 PM
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Ok thanks Jim. Interesting. I did notice that the nearby presence of the RFU had an affect on the ability of the GPS to acquire satellites.
Oct 27, 2017, 04:01 PM
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outkast1779's Avatar

High dollar install- need to confirm

Hey Jim,
I'm getting ready to install the RFU in a Ultra Flash Turbine Jet moving along at around 250MPH 200 MPH. Can/should I install a second RFU on the X10 for more coverage?

Since this is a composite model how do you suggest I place the antennas ?
Last edited by outkast1779; Oct 27, 2017 at 06:11 PM.
Oct 27, 2017, 05:54 PM
First of all, you can't do 250MPH with any turbine powered model. Your (our) turbine waivers have a speed limit of 200 MPH.

I would use two RFU's in the Ultra Flash because the turbine pipe is long, and there are a lot of onboard electronics for the turbine.

I would place one RFU in the nose of the aircraft with one antenna wire at the apex of the nose (curved) and the other antenna wire taped to the side of the nose, about 5" away from the nose. I would place a 2nd RFU either in the wing itself or (preferably) in the vertical, with the antenna wires 90 degrees apart.

Make sure that you do the range test, spinning the aircraft 360 degrees, and then check it on its nose 360 degrees.
Nov 14, 2017, 08:57 AM
I'll Fly Anything...

RFU SBus versus PPM

Good Day,

I use a number of RFU receivers with fixed wing models and X10+ Channel Expanders.

My question is about the use of RFU's programmed in PPM mode and used with small racing quadcopters.

Recent advanced in Flight Controller technology has begun precluding the use of PPM inputs and going forward only seems to support SBus of Spektrum protocols. As this may be more due to popularity of those two platforms, PPM is fading away. Sorry, couldn't resist the pun.

There are many who claim that SBus is faster than PPM, something to the tune of 10 milliseconds faster. Whoopee.

Question: With the RFU, it's plenty fast - whether programmed with SBus, Xtremelink, PPM, Spektrum or whatever, is there any difference in speed with this magnificent device?

Ross Wegryn-Jones

Loyal Xtreme Power Systems Afficianado
Nov 14, 2017, 11:10 AM
The SBUS protocol is about 15x faster than PPM. If your device can use SBUS, then use it! The RFU can handle anything thrown at it.
Nov 16, 2017, 10:51 AM
I'll Fly Anything...
Originally Posted by JimDrew
The SBUS protocol is about 15x faster than PPM. If your device can use SBUS, then use it! The RFU can handle anything thrown at it.
Holy ^%$#

Thanks Jim!