FrSKY R9M & R9MM combo - using as Redundant system

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Mar 2, 2018
18
1
#1
the instructions for this package are usless for non-tec guys like me. I have no idea how the R9MM receiver is connected to the main receiver in the plane, this goes in a Kappa 35. i need a wiring diagram showing me the connections to and from the two receivers. the mini receiver has 4 ports labeled ch 1 tru 4. it also has a 5 pin plug with s bus out, s port/f port, Gnd, v-in, and inverted s port. where do all thoes ports go? the package has a 4 pin plug with a plastic female connector that could hook to the 4 ports ch 1 -4. there is a 5pin plug that could be used for the other 5 ports. but where do they all go ?? video's showing redundant systems using other receivers show using a standard 3 wire connecton from one receiver to the other that wont work here. the receiver i'm trying to connect it to (the main receiver) is a GRX8.
Can any body help ??
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#2
It is my understanding that these Rx are not compatible. The R9MM uses the 900mHz radio frequency band and the GRX8 uses the 2.4gHz radio frequency band. What frequency band are you transmitting on?
 
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Mar 2, 2018
18
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#3
That is true, but part of the redundant package is the 900mHz plug in moduel that plugs into the back of the Taranis radio
that transmits in the 900mHz frequency, supposably to give you not only a redundant system but also the additional distance with the 900nHz frequency transmitter moduel and receiver. at least i think thats what they are advertising with this combo package (R9M & R9MM)
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#4
No that is not how it works. When you plug in the R9M TX module you turn off the internal 2.4 gHz and use the external plugged in TX RF deck, R9M.
I don’t see any mention of using 2.4gHz hardware concurrent with 900 mHz hardware. Nor do I see any redundancy on the 900 mHz band equipment. Can you link to the documents you reference?
https://alofthobbies.com/frsky-r9-mm.html
https://alofthobbies.com/frsky-r9m-transmitter-module.html

900 mHz has a lot longer radio wave propagation than 2.4gHz particularly in high humidity conditions at the cost of data rate transmission. As I read your understanding you will be relying on the single 900 mHz band at distance, as the 2.4 gHz signal will not reach as far as the 900 mHz signal. Loosing any perceived RF redundancy using both RF bands..

You can not hook up the R9MM to the G-RX8 receiver and expect redundancy from a 2.4 gHz band and 900 mHz band.

What you can do is hook up the G-RX8 (2.4 gHz) to a MX+ receiver. This gives you redundancy in that you have two separate 2.4gHz RF receivers placed at some distance from each other sharing a common PWM servo decoder in the G-RX8.
https://alofthobbies.com/frsky-g-rx8.html
https://alofthobbies.com/xm-plus.html

All the best,
Konrad

P.S.
Is this the combo you are looking at? I see no mention of redundancy.
https://alofthobbies.com/frsky-r9m-lite-r9mm-combo-pre-order.html

See Wayne's responce here to dual band use, post #5.
https://forum.alofthobbies.com/index.php?threads/frsky-r9m-r9mm-combo-using-as-redundant-system.594/

Edit: To add "no" to P.S.
Add Wayne's reponce
 
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Mar 2, 2018
18
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#5
OK so my assumption that this package would give me a redundant system is not accurate. I have the Frsky CPPN/SBUS decoder so now all i need is an additional receiver that will work as a redundant receiver ? Will the R-XSR 16 ch receiver work ?? This goes in my Kappa 35 so size is an isue. the R-XSR looks like it has a 5 pin adapter plug. please let me know if you would suggest another receiver. thanks so much for your help.
the module i have is not the "lite" its the red body one.
Tim
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#7
First off I don't know what a Kappa 35 is. How many channels do you need and and what signal the servos need PWM or CPPM/SBus.
The R-XSR 16 outputs CPPM/SBus to the servo. The R-XSR is the main receiver and would need a receiver such as the MX+ as the redundant receiver. These two Receivers would be connected via an SBus lead (standard -+s harness).

Any of these "RX" receivers will make a good primary receiver and are setup to use a second receiver as the redundant back up. I really like the RX8R pro with the MX+ as a back up receiver placed way in the back with the antennas sticking out the back at close to 90° to each other.
https://alofthobbies.com/radio/frsky-telemetry-system/redundancy-receivers.html
https://alofthobbies.com/frsky-rx8r-pro.html

And yes, you will need an SBus decoder on each standard PWM servo and ESC.
https://alofthobbies.com/frsky-sd1-sbus-converter.html
Or if you can fit a block decoder.
https://alofthobbies.com/frsky-sbus-decoder.html

Now I'm not sure why you want a redundant system (2 receivers) instead of a long range system (900 mHz).
A redundant system does not offer any range advantage over a simple single receiver. It does offer a more robust RF link in that reflective parts of the aircraft are less likely to totally block all the RF signal from the TX.

So are you concerned with the carbon and batteries in the aircraft blocking the antennas (redundant RX) or do you want longer range (900 mHz) for non- line of sight flying?
 
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Mar 2, 2018
18
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#8
sorry i didnt make my self very clear. the Kappa 35 is all carbon glider (Fuse & wings 3.5 m F5J) right now the antennas exit the fuse under the wing so i have DEAD SPOTS (the fuse is very small, about 36mm dia, hatch access about 27mm) so i dont have alot of room to move things around. i dont have to have more range as we fly line of sight, just thought it would be nice for the additional range .I'm using all digital servos, with the GRX8 receiver, i need 7 reg channels to operate the plane ( 2 ails, 2 flps, 1 elv, 1 rud and the motor ) in order to use ch 7 as a normal you have bind the GRX8 with a jumper between ch 1 and 2. now i still have ch 8 as SBUS out and port #9 as SBUS in. can i connect from the GRX8 to the backup receiver using the sbus to pwm decoder ? using either the XM+ or the R-XSR as backup receivers ??
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#9
Wow, you can get a flight battey through that small an opening (FAI F5J)?

I’m now using a G-RX8 in my 3.2 meter sport glider and have had no range issue with the RF link.
https://alofthobbies.com/frsky-g-rx8.html

In carbon fuselages I like to use these antennas as they help get the antenna out from under the wing.
https://alofthobbies.com/frsky-150mm-x-8mm-dia-replacement-antenna.html

Now the G-RX8 has a, in my opinion, a gross limitation. That is to be set up to accept a redundant RX it needs to be in SBus mode. This means that Ch7 output is dead and Ch8 is used as SBus out. To use more than 6 native PWM channels with the G-RX8 you need to keep it in normal mode. This means that one can not use a redundant RX with the G-RX8 in normal mode.

Now I think you can use the G-RX8 in SBus mode and use the first 6 channels from the RX bus bar. connect your Sbus decoder to the SBus out (Ch8) and assign these 4 PWM outputs Ch7 through Ch10.

Just spit balling here but I think we could add one of those SBus converters to the ESC assign it to CH7, with the G-RX8 in SBus mode, plug it into SBus output (Ch8).
https://alofthobbies.com/frsky-sd1-sbus-converter.html

Or for a cleaner installation put the SBus converter in the wing to drive the 4 PWM servos. This would result in only 3 wire going across the fuse/wing joint.

I don't understand why one woud want to use an R-XSR as the redundant (back up) receiver. But as it has an Sbus output it looks like you could use it as such ( a redundant RX).

Good to hear that the servos are digital.

All the best,
Konrad
 
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Mar 2, 2018
18
1
#10
can't tell you how nice it to talk to somebody who knows what thy'e talking about. can't do anything with modifying the wing, its molded carbonfiber, the wing harnes comes out at the bottom of the wing to a fixed plug that plugs into a fixed plug in the top of the fuse so when the wing is attached the plugs do also. because i struggle through this like its Greek i think what your telling me is, i could use the GRX8 in sbus mode, plug the decoder into sbus out of the GRX8. then i would plug in my ch 7 (L ail) to one of the 4 plugs on the decoder ( i was looking at the R-XSR only because of convince with the pig tail as plug & go) Then where does the R-XSR ( or whatever receiver i use for redundancy) plug in ?? to the sbus in on the GRX8 ? or into one of the 4 pins on the decoder ? at some point after my brain recovers, i'll need to know if there is a video that shows me how to assign channels to the decoder.
https://get.google.com/albumarchive...ClfRo_RDQm-XpvVnw7N6nZEYqRkkbLne_q?source=pwa
this link could help you see what i'm working with.
Thanks again for your help.
Tim
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#11
Thanks, but I hate to shatter your opinion of me, but I really don't know much about these high performance gliders. As to Fr Sky I can usually get things to work but often after a bit of trial and error. This is normal for most technical endeavors.

Yes, with the G-RX8 in S.Bus mode you plug the S.Bus signal from the redundant RX into (S.Bus in). If you need more than 6 channels output from the GRX8 in S.Bus mode you would plug the SBus compliant devise into S.Bus out (Ch 8). From your post this would be the 4 channel S.Bus decoder.

If working with S.Bus you need one of these.
https://alofthobbies.com/frsky-servo-channel-changer-sbus-cppm.html
It tells the servo, or whatever, what data packet to read from the SBus serial port.

If this was my set up and I wanted to use the GRX8 I'd put the GRX8 in S.Bus mode. In the TX I'd assign all the wing servos to Ch1- Ch4 as these are the high precision channels coming out of the GRX8 RX. Rudder and elevator would be assigned to Ch5 and Ch6. What we get is all the primary flight controls coming directly off the RX in PWM mode. Less chance of a wire or plug failure.

This still leaves us with the question of what to do with the ESC? I'd convert the ESC to be compliant with SBus by soldering on this converter.
https://alofthobbies.com/frsky-sd1-sbus-converter.html
Once this was done I would, with the S.Bus Channel Changer, assign the ESC to channel 7. Make sure you have also assigned the throttle command (I use the left slider) to output on channel 7 in the TX. Plug the newly converted SBus ESC into S.bus out (RX pin Ch8).

You will need to make a very long 3 wire Male to Male extension to place the MX+ RX in the tail. One end of this extension will plug into the 3 pin block (you will have to solder this onto the Mx+) and the other end plugs into the S.Bus in port. As there is no real power being transmitted you can use the thinner wire to make this extension. I like the twisted 28 AWG wire. I'm make it about 50mm longer than the distance between the GRX-8 and the MX+.
https://alofthobbies.com/servo-wire.html
https://alofthobbies.com/xm-plus.html

Some other links;
https://forum.alofthobbies.com/inde...eceiver-is-not-ready-for-the-mass-market.227/
https://forum.alofthobbies.com/inde...wm-mode-continuous-digital-servo-chatter.452/
https://alofthobbies.com/taranis-plus-user-manual.html
http://rc-soar.com/opentx/setups/esoarplus/index.htm


All the best,
Konrad

May I ask who you are (background)? As you seem to use videos, I assume you are a lot younger than myself. This is not a judgement, rather I'm trying to ascertain my audience. All I know about you is that you think you aren't tech savvy and you fly F5J.
 
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Mar 2, 2018
18
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#12
Well i'm located in Mt Vernon WA. been flying gliders for 30 + years, just keep trying not have to learn the techie stuff so now i'm trying to catch up to all the cool stuff thats out there. now retired, i was a West Coast supervisor for an industrial construction company. probably not younger than you , graduated high school in 1965. now back to the chalange.
Let me se if i can do a better job of narrowing down what i'm trying to do.keep the # of components in the plane as few as possible and minimized the amount of solder joints & wiring. after working my way through all your suggestions i think you need to know my radio setup.that ( open tx clinic ) site front page is almost idenical to my set up. ch1=esc ch2=L ail ch3=Elv ch4=Rud ch5=Rail ch6=Rflp ch7=Lflp. my motor is activated from sf. i replaced sf with a momentary swich. then any time during launch if you have to abbort for any reason just let go and motor is off, so many accidents at launch could have been minimized if the pilot could have goten the motor shut off sooner. all my planes are set up this way so i would like to get this set up so all thoes channel assignments stay the same. i believe you convinced me that the RX8R Pro would be the best as the main receiver, then all my hookups remain the same, now i use the GRX8 or the XM+ as the secondary receiver, the advantage using the GRX8 is it gives me altimeter, then would i still nee the decoder ? and how would the hook ups look in this configuration.
sorry i keep bothering you but i don't know anywhere else to go.
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#13
You are a lot like me, ok 15 years older. You come out of a school system that did not teach to the test. And you actually made stuff in the real world other than piles of paper work.

I graduated high school in 1979 (I think). Been flying RC for 40 years. Was a machinist for half my working years. Last worked as a Field Service Engineer, flight testing the 787, at Boeing. Retired early.

The GRX8 used as a redundant RX would NOT need the decoder. The GRX8 would be in S.Bus mode. All sixteen channels would be available from the S.Bus port (S.Bus out [ch8]). Don't know if the vario would work, as normally one turns off the telemetry from the redundant RX. I know at least one RX needs to have the telemetry suppressed. It is normally the redundant RX that has the telemetry suppressed.

As far as hook up, I think all you need is that long 3 pin Male to Male (Jr style connectors) S.Bus lead.

I've never tried to set up a plane with the redundant RX sending telemetry and the primary RX having the telemetry turned off.

I will say I don't like using the vario as I find them very annoying. I find myself flying the tone rather than the sailplane.

Glad to help.
Now it is often a good idea to get a second perspective, particularly when dealing with software and system integration. This is because there is often more than one way to address the issue.
https://openrcforums.com/forum/index.php?sid=ca880f41edfe8de16f5ba462f763ed35
 
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Mar 2, 2018
18
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#14
still a little fuzzy on hook up. I see 3 scenarios. use the RX8 PRO as the main receiver and use the RXSR as the redundant.In this case the connection would be from the s bus on the RX8 to the s bus out (ch 8) on the GRX8, and hope for the altitude function. Or use the RX8 PRO for the main and the RXSR as the redundant (the advantage here being it comes with a pigtail & plug) i assume it also would plug into ch 8 on the GRX8. Or go with the R9M & R9MM package and make thoes little solder connections. Just got your last post while i was writing this. i guess we have two post's going here ? so what Wayn is saying is the 900 system will work with the 2.4 ?
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#15
Yes, Wayne is saying that you can set up theTX to transmit on both the 2.4 gHz and 900 mHz at the same time. He thinks that since the output of the 9mm(RX) is S.Bus it can be used to link the the 9mm to any redundant capable 2.4 gHz receiver. I don't know this but I'd take Wayne's word for this.

Now what I have an issue with is, I don't see what the benefits would be to dual RF bands. I'd think that for range and use in obstruction environments the 900 mHz band is what one would want. I don't understand the desire to be draining the TX batteries twice as fast supporting the RF links on both the 2.4 gHz and 900 mHz bands.

You are aware that the RX8Rpro, RXSR and G-RX8 are all primary redundant capable receivers?

The RX8Rpro (primary) and RXSR (redundant) receiver combination would use the S.Bus output from the RXSR to the S.Bus input on the RX8Rpro.

Not sure I follow the second scenario But I think you are trying to say is use the G-RX8 as the redundant receiver with telemetry left on (keeping the vario option) connecting this receiver from the S.Bus out (ch8) to the RX8Rpro S.Bus in. With the telemetry on the RX8Rpro turned off so as not the interfere with the telemetry (vario) from the G-RX8.
Rx to RX.jpg
 
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Mar 2, 2018
18
1
#16
yes, i see that using the 900 system is not much of an advantage in my case, did'nt know about the additional battery consumption. so i will try the RX8 PRO as primary with GRX8 as redundant and see if i can get the altimeter function. if not, i will still use the RX8 PRO as primary and use the RXSR as redundant. i have thoes components on the way. i will be out of town for the rest of the week but will keep you posted with the progress. Thanks again for all the help.
I'm going to the AMA Expo if your going maybe we coul meet up. i would think Aloft would have a booth there.
 
Mar 2, 2018
18
1
#17
Yes, Wayne is saying that you can set up theTX to transmit on both the 2.4 gHz and 900 mHz at the same time. He thinks that since the output of the 9mm(RX) is S.Bus it can be used to link the the 9mm to any redundant capable 2.4 gHz receiver. I don't know this but I'd take Wayne's word for this.

Now what I have an issue with is, I don't see what the benefits would be to dual RF bands. I'd think that for range and use in obstruction environments the 900 mHz band is what one would want. I don't understand the desire to be draining the TX batteries twice as fast supporting the RF links on both the 2.4 gHz and 900 mHz bands.

You are aware that the RX8Rpro, RXSR and G-RX8 are all primary redundant capable receivers?

The RX8Rpro (primary) and RXSR (redundant) receiver combination would use the S.Bus output from the RXSR to the S.Bus input on the RX8Rpro.

Not sure I follow the second scenario But I think you are trying to say is use the G-RX8 as the redundant receiver with telemetry left on (keeping the vario option) connecting this receiver from the S.Bus out (ch8) to the RX8Rpro S.Bus in. With the telemetry on the RX8Rpro turned off so as not the interfere with the telemetry (vario) from the G-RX8.
View attachment 1214
I think i have landed on a solution to my redundant sitiuation. Well use my GRX8 as the main and R-XSR for the redundant. I have them wired up and both bound to the reciever.
Yes, Wayne is saying that you can set up theTX to transmit on both the 2.4 gHz and 900 mHz at the same time. He thinks that since the output of the 9mm(RX) is S.Bus it can be used to link the the 9mm to any redundant capable 2.4 gHz receiver. I don't know this but I'd take Wayne's word for this.

Now what I have an issue with is, I don't see what the benefits would be to dual RF bands. I'd think that for range and use in obstruction environments the 900 mHz band is what one would want. I don't understand the desire to be draining the TX batteries twice as fast supporting the RF links on both the 2.4 gHz and 900 mHz bands.

You are aware that the RX8Rpro, RXSR and G-RX8 are all primary redundant capable receivers?

The RX8Rpro (primary) and RXSR (redundant) receiver combination would use the S.Bus output from the RXSR to the S.Bus input on the RX8Rpro.

Not sure I follow the second scenario But I think you are trying to say is use the G-RX8 as the redundant receiver with telemetry left on (keeping the vario option) connecting this receiver from the S.Bus out (ch8) to the RX8Rpro S.Bus in. With the telemetry on the RX8Rpro turned off so as not the interfere with the telemetry (vario) from the G-RX8.
View attachment 1214
I think i have landed on a solution to my redundant sitiuation. Well use my GRX8 as the main and R-XSR for the redundant. I have them wired up and both bound to the reciever. I have the GRX8 bound in the PWM mode, allowing ch 7 to work as ch 1 thu 6 work. also have the altimeter working. all indications are everything is working, the GRX8 green light and the R-XSR blue light. but i can't figure out how to test as the R-XSR has no external plug to hook up to a servo to verify. any ideas ?
Tim
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#18
To see if the redundant RX is working I can only think of using an S.Bus compliant device and Y splice it into the S.Bus harness between both RX's. Mayby wrap the main antenna in aluminum foil?

I thought that the G-RX8 needed to be in S.Bus mode to allow the use of a redundant RX.

I fear you are just using the G-RX8 as a normal receiver (No redundant benefit from the R-XSR) as the G-RX8 is not capable of taking in S.Bus data unless in S.Bus mode.


This is a good question for FrSky. I'll dig into the documentation a bit more.

I think with firmware 170922 you CAN use the redundantcy feature while in PWM mode! I may have learned something new, Thanks!
 
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Jan 23, 2018
705
41
San Francisco
#20
I want to be clear. Lost sensor, (telemetry lost) is really the receiver in the TX saying it has lost the signal. It has no way of knowing if the receiver in the plane has lost contact.

Since the down link is weaker than the up link it is a good indication that you are fly a bit out of range.

In this test the main RX is also sending telemetry the fact that itis showing degraded signal strength is a good indication that you are blocking the main RX's antenna, and you are using the data stream from the redundant RX to control the servos.

Did you do arange check with the main RX blocked?