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FR-Sky Dual frequency setup and redundancy

Discussion about Tx, Rx, Servo's, Batteries, Chargers, and all the other things we like to talk about..
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paulj
Posts: 54
Joined: 23 Dec 2018, 17:51
Location: North Wales

FR-Sky Dual frequency setup and redundancy

Post by paulj »

Good morning all!
I am looking a the options for running a dual 2.4GHz and 868MHz setup with my Taranis. These are the options I think are available:
Common to both options:
- Get a module for the transmitter: FrSky R9M 2019 ACCESS 868MHz Module

Option 1:
- Slave a X4R receiver (or other 2.4GHz receiver with SBUS) to a master R9-Slim+ receiver
- Use one battery pack, or two packs and redundancy with diodes (as explained elsewhere in this forum)
- Telemetry through the R9-Slim receiver

Option 2:
- Use an FR-Sky Redundancy Bus 10
- One or two packs, with separate inputs to the Bus-10
- sbus input from two receivers into the Bus-10
- Telemetry through one of the receivers
- Option 2 advantages: overload protection on the servo outputs

Here are my questions:
- Are there any options I haven't considered (exclude options like buying the new dual band transmitter coming out soon!)?
- With option 2, how does the redundancy bus decide which receiver to take as correct? Is the assumption that one of them is a master receiver, and in the event of losing signal from this one, then the other receiver will be used.I think this is the arrangement with the receivers in option 1 - use the R9-Slim+ signal, and if there isn't one, then switch to the slave 2.4GHz receiver.
- Can I use ACCST with the 2.4GHz side, and ACCESS on the 868MHz side? I don't see any reason not to, since they are independent but I always prefer a positive confirmation!I am quite happy with the ACCST kit I have, but if I am going to buy new bits for the 900MHz side, I don't see any reason to flash them to use ACCST (unless there are other reasons which make the ACCST a better choice).
- Are there any caveats I haven't recognised?

Based on these factors, I think that option 2 is the safest, due to the overload protection on the servos, with option 1 a better choice if space is at a premium. Since I am exploring this as I am finally getting around to building my Moswey, I don't think I have any space issues (compared to my sport gliders)!

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Barry_Cole
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Location: Hampshire UK

Re: FR-Sky Dual frequency setup and redundancy

Post by Barry_Cole »

Paul,
I have sent you an e-mail.

BC

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paulj
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Joined: 23 Dec 2018, 17:51
Location: North Wales

Re: FR-Sky Dual frequency setup and redundancy

Post by paulj »

Quick update in case anyone else is following this thread, after receiving very helpful advice in a phone call with Barry!

Advice:
- One option I didn't list was to run the glider on one receiver, with one pack. In Barry's experience, backed up by other FRSky users, there is no need to consider redundancy as a general rule, and more equipment could mean more to go wrong.
- If you do consider fitting a redundancy bus, then look at the RB 20 - it has better a range of features.
- ACCESS receivers have been reported as delivering better range than ACCST receivers, or certainly better than some of the earlier models. Apparently hardware changes to the later ACCST receivers improved their range as well.

My considerations:
- If I do lose the 2.4GHz signal, the 868MHz backup is good for safety of the model.
- I don't think there is much risk of equipment failure as such, so I am not worried unduly about the risk of losing a receiver or indeed a pack. It would also mean I don't see the need for two receivers on 2.4GHz. Barry did say he had a two receiver setup in his tug, which were configured to control the surfaces on each side of the model, so if one receiver did pack up, there is still a degree of control to get the model down again.

At the moment, I haven't made any final decision, and won't be buying any equipment - I have to build the glider first (after building the workbench). It was very helpful to consider the options, and also to have Barry's advice - I now feel better informed than previously.

If anyone else feels like adding anything, please do!

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Cliff Evans
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Re: FR-Sky Dual frequency setup and redundancy

Post by Cliff Evans »

I have an RB20 redundancy box and two X8r receivers and two 5000mah Jeti battery packs in my 1/3 scale T21. All works well.

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paulj
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Joined: 23 Dec 2018, 17:51
Location: North Wales

Re: FR-Sky Dual frequency setup and redundancy

Post by paulj »

Cliff Evans wrote:
> I have an RB20 redundancy box and two X8r receivers and two 5000mah Jeti
> battery packs in my 1/3 scale T21. All works well.

Have you ever considered using dual frequency as well, so rather than two 2.4GHz receivers, have one 868MHz receiver and one 2.4GHz receiver? How does the RB20 use the receivers - is one the primary receiver and this is used unless there is no signal in which case the second is used, or does it look for the one with the strongest signal?

PS: BBCode is showing as off when I reply - odd since my reply to your private message yesterday shows that it was on!!

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Cliff Evans
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Re: FR-Sky Dual frequency setup and redundancy

Post by Cliff Evans »

BBCode settings must be in your private setting somewhere as it is on globally! Will look into it for you

Basically it will use the strongest signal from whatever receiver. You must have one of the receiver's with telemetry off in this setup with the older receivers. Access has solved this problem. I am in the process of switching all my receivers over to Access. I have the new 10 channel Rx which is really quite nice, two battery inputs! will be using the new Archer RS receiver as soon as they release it as redundancy.

With regards to using 868Mhz as well, I just dont see the need!

SP250
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Joined: 18 Mar 2015, 06:19
Location: North Shropshire

Re: FR-Sky Dual frequency setup and redundancy

Post by SP250 »

How many people have a transmitter putting out 868mHz as well as 2.4????
I've not heard of a single one which does this and certainly not a Taranis.
Dual Multiplex Rx's in one case is fine for my modelling requirements.

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Barry_Cole
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Location: Hampshire UK

Re: FR-Sky Dual frequency setup and redundancy

Post by Barry_Cole »

SP250 wrote:
05 Aug 2020, 17:01
How many people have a transmitter putting out 868mHz as well as 2.4????
I've not heard of a single one which does this and certainly not a Taranis.
Dual Multiplex Rx's in one case is fine for my modelling requirements.
You can put a 868mHz module in the back of any Taranis, and transmit both.

Many peple doing it round the world.

8-) 8-) 8-) 8-)

BC

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paulj
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Joined: 23 Dec 2018, 17:51
Location: North Wales

Re: FR-Sky Dual frequency setup and redundancy

Post by paulj »

I believe the top of the range jeti transmitters have an option of dual frequency operation built in. They prioritise the signal on 2.4GHz, as the latency is apparently less on the higher frequency.

FrankS
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Joined: 18 Mar 2015, 14:29
Location: Gloucestershire

Re: FR-Sky Dual frequency setup and redundancy

Post by FrankS »

Yes on the Jeti's you can plug a "868 MHZ" satellite into a receiver or power distribution box as a back up.

Recently at the club we've had a couple of new members turn up with Frsky gear using 868 MHZ modules and receivers as they understood 2.4 GHz had poor range................................

I can't remember anybody at an aerotow every flying out of radio range, regardless of brand.

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