Scale Soaring UK

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)!

Paul,
I have sent you an e-mail.

BC

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!

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.

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!!

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!

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.

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.



BC

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.

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.

The new Frsky Access system boasts a better range than most on 2.4!

OK, seems there are systems about.
I've not heard of them because I have a good 2.4 system in the first place and don't need to fix problems.
I am still amazed by the number of posts on different forums of people having to re-bind, re-flash, lots of different software bug fixes and B****r about with the FrSky gear, that puts me off straight away. If it was right in the first place it wouldn't need upgrades.
But it does look like a solution to a problem that doesn't exsist really.
If the 2.4 system was an improvement on 35 mHz why should 868 be necessary?
Complication and expense for its own sake - just buy a good 2.4 system in the first place.
I guess I had a bad day yesterday and grump over - I'll get me coat now.

John M

SP250 wrote: ↑06 Aug 2020, 08:40 OK, seems there are systems about.
I've not heard of them because I have a good 2.4 system in the first place and don't need to fix problems.
I am still amazed by the number of posts on different forums of people having to re-bind, re-flash, lots of different software bug fixes and B****r about with the FrSky gear, that puts me off straight away. If it was right in the first place it wouldn't need upgrades.
But it does look like a solution to a problem that doesn't exsist really.
If the 2.4 system was an improvement on 35 mHz why should 868 be necessary?
Complication and expense for its own sake - just buy a good 2.4 system in the first place.
I guess I had a bad day yesterday and grump over - I'll get me coat now.

John M

The flashing of Frsky is not down to bugs it is all updates, most people using Frsky go from the native Fros to OpenTX as the OpenTX is a much better system. The OpenTX team is constantly working on the software to add to it and improve it. Frsky is not the only company to allow this with their systems. I have had Frsky for years now and have never had a problem with it and for how long it takes to update the system to the latest firmware it really is not a problem. The new access system allows you to update "over air" so now if you use the latest receivers, no matter where they are in the model you can update the firmware just by transmitting it to the receiver. It is no different really to Microsoft or Apple updating their systems all the time. It's not a question of the system being "right" in the first place, the system is constantly evolving. It is only my opinion but I believe Frsky is probably one of the best systems on the market, for the price, it outperforms even the big boys!

Hi John,
As originator of this thread, I think I should respond to your post, because you may have the wrong impression about FR-Sky equipment as a result of my original post.
- I have never had any issues with range on 2.4GHz with my FR-Sky equipment. I have used a number of different receiver types in a number of different types of models sometimes at great range, with no issue at all.
- I have seen the approach offered by Jeti, and just wanted to explore the opportunities presented by FR-Sky for creating some redundancy (there is a new Horus transmitter coming soon with both transmitter modules built in as well). I now understand there are systems in place which allow for battery redundancy, for receiver redundancy and also protection against servo overload.
- For my application, there is really no need to consider using any of them! Experience from other FR-Sky users confirms this. One 2.4GHz receiver set up correctly has a greater range than my eyesight, even with 1/3rd scale models. Reliability is not an issue to be worried about.
- Regarding people all over the internet struggling to bind their equipment - I have seen issues reported by many people with different systems struggling with this - it's not FR-Sky specific . A couple of years back, there were differences between EU and non-EU firmware, and you had to make sure your transmitter and receivers were flashed with the same level firmware. This was not fully appreciated, and led to people failing to bind to their receivers. In fact, flashing the firmware is a trivial task when done properly, and it makes sense (IMHO) to take advantage of the work done to ensure bug free reliable firmware and to keep everything up to date.

One of the biggest selling points of FR-Sky equipment in my view is OpenTX. I have been a firm advocate of open source for many years - for example my home computer systems have run linux since 1996. OpenTX is an excellent piece of software, and ensures that there are no limits from the transmitter software preventing me from creating any program I like. As a previous Multiplex user, this is great, but I do understand that for many it is too much faff and they aren't interested.

One final comment - I understand that the advantage of 2.4GHz over 35MHz is related to frequency hopping and bandwidth. No longer a need for a pegboard, no practical limit to the number of models in the air at once, and enough space in the signal for downstream telemetry and (I guess) lower latency. Downside of 2.4GHz over 35MHz - the range of the latter is greater. 868MHz is finding fans in the worldwide FPV community due to the very long range possible (up to 10km). Of course flying out of sight is not legal in the UK, and shouldn't be practised, so this is kind of unnecessary.
Anyway - no need to get your coat! I hope you have a better day today!

Thanks for the reply Paul - interesting to get your reasons for looking at the multi frequency issue.

Being a Multiplex user for 25 years now, I am happy that people are enjoying the freedom of the Open TX software, as it started out as the MPX 4000 which many said was unfathomable when it first appeared.
Yet here we are a couple of decades on and whilst the OTX system is changed out of all recognition from the 4000, I agree that it is the most capable system I have used or looked at (can't speak for Jeti as I have not used it).
Many more people can now get their head around it thanks to the rise of forums, FaceBook and Mike Shellim etc..
Each to their own eh.

Yes a much better day today - confirmation from the speciallist that I am not losing the sight in my right eye.
John M

I had a 4000 for years. When I got it, it took me 3 days to make a servo move, after that it gradually got easier. Back in those days Mpx were friendly and you could talk to them, if you needed help. When I saw FrSky and Open TX, I swapped over immediately. Programming was much the same, and there was and still is an army of people out there to help, and advise. Added bonus was and still is, that the gear is a fraction of the price of Mpx.

When things need updating it is usually straight forward, and in many cases if you do not want to, you do not have to.

Yes I am a convert.



BC

SP250 wrote:
> Yes a much better day today - confirmation from the speciallist that I am
> not losing the sight in my right eye.
> John M

That’s a relief John - I hope the issues you have with your eye are sorted out quickly.

Best regards,
Paul

Cliff Evans wrote:
> The new Frsky Access system boasts a better
> range than most on 2.4!

How when everybody is working to the same standard, do the ACCESS receivers have some form of improved signal filtration and amplification? Or is it down to better software reducing the data rate?

Both telemetry and control range increased by 40% according to Frsky. If you want details contact them directly as I am not a techy!!

Since this is about redundancy, which system would you guys think provides the best reduncancy features, on a large model with split elevators/ailerons etc.

1. Two receivers- one side of the plane on each receiver, each fed from a Lipo or suitable battery.
2. A single receiver but twice the number of channels, provided with a dual lipo feed through a battery backer or similar diode reduncdant set up.

Obviously in case 1, there is double the chance you will lose one side of the plane as its two systems. But in case 2, the single point of failure is the receiver as theres only one.

Swings and roundabouts? Im thinking myself that case 2 is probably the best system? Discuss. Cheers,!

Sorry, if its off topic, mods feel free to move it to a new topic if you think it needs it.

Frsky makes a redundancy bus system that utilizes two batteries and two receivers. There are two units RB10, https://www.t9hobbysport.com/frsky-redundancy-bus-10 and RB20 https://www.t9hobbysport.com/frsky-rb20-redundancy-bus. I use the RB10 in my 1/3 scale T21 and have been for the last three years. They have new system coming soon to replace these two systems. The RB30 https://www.frsky-rc.com/product/rb30/ and the RB40 https://www.frsky-rc.com/product/rb40/

With the Access system you can have up to three receivers bound to one model, each can have their own power supply. Only one will have a direct connection to the servos, the other two receivers are connected to the main one via Sbus which in the event of loss of signal even if the battery goes the servos are always connected to the other two receivers so redundancy is pretty good.


In the not too distant future, there is a new transmitter planned that has both 2.4 and 900mhz on board that can be used together to transmit to two separate frequencies simultaneously.